Category: Analysis

Anything that I have tested empirically, or explain with detailed calculations, or just generally bother to get all the facts straight.

Post #1657: The World Turned Upside-Down, Part 2

 

Background:  <=24¢/KWH

Yesterday I calculated the cost of running a Prius Prime on electricity versus gasoline.  At the current U.S. average of $3.24 for a gallon of gas, electricity is the cheaper fuel for a Prius Prime if and only if it costs 24 cents per kilowatt-hour or less.

That calculation was prompted by the claim that in much of New England, it’s now cheaper to run a Prime on gas, rather than electricity.  As it turns out, that’s true.  As of September 2022, most of New England faced electricity prices that exceeded that threshold.  (As did the average price in California.)  I’m guessing that New England rates have gone up further since September, owing to a recent spike in the price of natural gas.

Source:  US EIA.

In a previous rant (Post #1548), I had already noted how expensive public charging stations were.  Not only did I find the one I tried to use to be both baffling and unreliable, you can pay anywhere from $0.50 to $1.25 per KWH for the privilege of using one.  Even last summer, when gas was expensive, it was cheaper to buy gas for the Prius Prime than to charge the battery at the commercial charging station I visited.

I’ll note in passing that there didn’t seem to be anything unique about the Prius Prime in this gas-versus-electricity calculation. I did the same calculation for a PHEV Volvo getting gas mileage about half that of the Prius, and came out with just about the same break-even price for electricity compared to gasoline.  The Volvo simply uses more of either gas or electricity per mile.

The upshot is that, at current gas and electric prices, some fairly large segments of the public will not see fuel cost savings from electric transport.  At the moment, that’s pretty much the entire population of New England and California.  (Though I did not factor in generally higher gas prices in California.)  And, likely indefinitely, that includes people who can’t charge at home and so must use a commercial charging station.

How large?  California and New England together account for about 14% of the U.S. population.  More importantly, near as I can tell, about a third of U.S. residents live in something other than owner-occupied or single-family housing.  Assuming those folks typically have no option other than commercial charging stations, that means at current gas and electric rates, something close to half of Americans will see electricity as a more expensive motor fuel than gasoline. 

I’m a big believer in electric transport.  But I wasn’t quite fully aware of the large fraction of the population for which there are no fuel cost savings in switching to electricity.  Sure, eventually apartment buildings might all come with chargers.  And sure, gas and electricity prices will vary over time.  But right here, right now, electricity is the cheaper motor fuel for only about half the population.

Tesla?  No thanks.

Which got me to thinking about a name that’s been in the news these days:  Tesla.

When we were shopping for our last car, and eventually settled on the Prius Prime, we considered going fully electric.  But I can’t recall giving even a moment’s thought to getting a Tesla.  And offhand, I couldn’t quite remember why.

So I took a look.

Oh, yeah, it’s because I’m cheap.  And because we buy our cars purely to be practical transport.

In any case, here’s the head-to-head comparison between the Prius Prime and the cheapest Tesla, the Model 3 rear-wheel-drive, courtesy of fueleconomy.gov

To boil it down, the cars are equally efficient as electric vehicles, and are the same size (same total interior volume).  But the Tesla costs almost $20K more, and has less than half the range.

The Tesla is faster, for sure.  But in Northern Virginia traffic, that’s more-or-less completely irrelevant.  My zero-to-sixty time isn’t set by my car, it’s set by whatever pace the inevitable traffic dictates.

I’m sure there are some bells and whistles on the Tesla that you don’t get on a Prius Prime. But, to tell you the truth, I don’t much like the ones we got on the Prius.  The very first thing I switched off, from the factory settings, was the automatic-steering function in cruise control.  I guess if I’m driving my car, I want to be driving my car.  Not having the car second-guessing where I want to be on the roadway.

And, to be fair, the Prius lacks snob appeal. It’s a pedestrian workaday vehicle, suitable for middle-class people who have some sense of concern for the environment.  It’s also exceptionally cheap in terms of lifetime cost-of-ownership.  Or so said Consumer Reports, at some point.

But with a Tesla, you can user their network of superchargers.  And if you have to pay for that, you’ll pay an average of $0.28 per KWH.  (That, per a 2021 article in Motorbiscuit.)  And, duly noted, $0.28 > $0.24.  So even with that dedicated network of branded charging stations, at today’s prices, you’ll pay more to fuel your car with electricity than with gasoline.

But the environment …

In America, we burn an average of 600 gallons of gasoline, annually, per licensed driver.  (Calculated from this reference and this reference).  Driving a Prius Prime, I’m guessing that my wife and I are down to maybe 25 gallons each, per year.  (I have to guess, because we go so long between tanks that neither of us could remember when we last bought gasoline.)  That’s the result of driving mostly on electricity, and otherwise driving an extremely efficient hybrid.

In theory, sure, we could reduce that 25 gallons down to zero by going fully electric.  But, honestly, in the context of my fellow Americans, I can only feel but so bad about the 25 gallons.  And that annual quarter-ton of C02 emissions from driving is probably not the worst environmental sin I commit.

But, as importantly, right now, one of the biggest constraints to electrifying the U.S. fleet is the lack of battery manufacturing capacity.  All the majors are now going full-out to build more battery factories.  There just are not enough traction batteries available to electrify the entire U.S. fleet, and there won’t be for years to come.

So the other way to think of the Prius Prime is that it makes efficient use of a scarce resource:  EV batteries.  The same amount of batteries that will build one EV Tesla Model 3 will build about eight PHEV Prius Primes.  Those eight Primes, displacing standard gas cars, will have a far larger environmental benefit than that single Tesla.

Moreover, that big battery, in the Tesla, is mostly wasted, in the sense that the driver will rarely use the entire capacity of the battery.  By contrast, the PHEV Prius Prime has a much smaller battery, that is fully discharged far more frequently.

From that standpoint, EVs are … wasteful.  As long as lack of battery capacity is a hard constraint on electrifying U.S. transport, we’d get a lot more environmental bang-for-the-buck out of PHEVs than EVs.  For the simple reason that a PHEV has a small battery, and uses it hard.  While an EV has a big battery that is hardly used.

Bottom line:  I just don’t see the fundamental value proposition in a Tesla.  Which means, to me, that people by-and-large were not choosing it based on a simple dollars-and-cents calculation.  And if image was a big factor in the choice, well, based on what I’ve been reading in the newspapers of late, Tesla may face some challenges moving forward.

Post #1656: The World Turned Upside-Down

 

Today my wife came across a thread on PriusChat in which a New Englander claimed that it now cost more to run his Prius Prime on electricity than on gasoline.

After I got done scoffing, I decided to look up the data.  Actually check the facts.  Just as a last resort.

And, in fact, that’s plausible.  With the recent declines in the price of gasoline, and sharp spikes in electricity prices in New England, it’s entirely possible that running a Prius Prime on gas is now cheaper than running it on electricity in that area.

Let me just chuck out a few numbers here, all based on the current EPA ratings of 4 miles per KWH and 54 miles per gallon for a Prius Prime.

First, it’s just math to figure out the break-even price of electricity, for any given cost of gasoline.  That is, the price at which it would cost you the same to power the car with electricity as with gasoline.  Because a gallon gets you 54 miles, and a KWH gets you 4 miles (per the U.S. EPA), just multiply the price of gas by (4/54 =~) 0.074.  So running the Prius Prime on $4/gallon gas costs the same as running it on electricity costing ($4 x 0.074  =) 30 cents per KWH.

Like so.  The “break-even” price of electricity just shadows the actual price of gas:

Source:  Gas price data from the St. Louis Fed FRED system.

Historically, at least in my area, that gasoline-equivalent cost was well above the actual price of electricity.  Hence, the fuel cost for electric-powered miles was well below the cost for gas-powered miles.

But now?  In, say, Boston?  Not so.  Take the red line off the prior graph — that’s your gasoline-break-even cost of electricity — and compare it to the actual cost of electricity in Boston and in the Washington DC area.

Source:  Electric rates via the St. Louis FRED system, e.g., DC electric rates.

And, sure enough, of late, the precipitous drop in gasoline prices, combined with the spike in New England electricity rates, has made it noticeably more expensive to run a Prius Prime on electricity, than on gasoline, in that area.  Although, as you can see from the very bottom line, it’s still cheaper to fill up on electricity than gasoline in the DC area.

Discussion

Apparently the spike in New England electric rates is due to a spike in U.S. natural gas prices, which, in turn, seems to be blamed on the war in Ukraine and the resulting spike in European gas prices.  The general idea being that the New England area is heavily dependent on natural gas for electricity production.

Either way, prices in the natural gas market now seem to be easing.

On the one hand, this raises an interesting advantage of having a true dual-fuel vehicle like the Prius Prime.  Within the limits of your battery capacity, your fuel cost can always be the lesser of the gas or electric per-mile rate.  You are protected from price spikes in either the gas or electric markets.

The question is, is the Prius Prime something of a special case, owing to its overall high efficiency? Or, does this have any strong implications for the per-mile cost advantages of electric vehicles in general?  I think the answer is, I think, the latter.

So, let me do the same calculation on a more typical U.S. vehicle.  Offhand, let me choose a PHEV Volvo, getting a pitiful 2 miles per KWH or equally pitiful 26 miles per gallon of gas.

Source:  2022 Volvo from Fueleconomy.gov

But the key here is “equally pitiful”.  The conversion factor from gas price per gallon, to the equivalent cost in electricity, is calculated just as it was for the Prius.  In this case, with 26 MPG and 2 miles per KWH, the conversion is (2 /26 = ) 0.077, virtually identical to what it was for the Prius.  And that’s because the Volvo uses just about twice as much gas, and twice as much electricity, as the Prius does.

Equally pitiful mileage on either gas or electric.  Which means that, as with Prius Prime drivers in New England, Volvo drivers in New England will also now find it cheaper to run on gas instead of electricity.  Sure, they’re paying twice as much per mile as Prius Prime drivers.  But that’s true whether they are burning gas or electricity.

I should probably do another one or two, to make sure that wasn’t an accidental cherry-pick.  But I’m guessing that what that sharp-eyed New Englander calculated for his Prius Prime applies to much of the dual-fuel gas-electric fleet.  With gas as cheap as it is now, there are spots in the U.S. where the fuel cost of gas is lower than the fuel cost of electricity.

In prior posts, I already showed that recharging your car at typical commercial-charger rates already costs more than running it on gasoline.  So if you don’t have a home-recharge option, or can’t recharge for free, there are no fuel savings from converting to electricity.  This means a significant fraction of the U.S. market may have little financial incentive to go electric.  This latest analysis just shows that unless those electrical rates come down, entire geographic areas of the U.S. will be in the same fossil-fuel-powered boat.

Post #1654: Testing eyeglasses and sunglasses for UV protection. Part 1, the set-up.

I’d like to know the level of protection from ultraviolet rays that my current eyeglasses and sunglasses provide.  In this post, I don’t actually do the test, but I set up all the background information.  The test has to wait for materials to arrive from Amazon. Continue reading Post #1654: Testing eyeglasses and sunglasses for UV protection. Part 1, the set-up.

Post #1641: Of Freon and Schrader Valves

 

Let me get to the punch line first, and tell the story second.

Yesterday, I found out that:

  1.  I own about $5,000 worth of R-22 refrigerant, a.k.a., Freon.  That’s at full retail, the price I’d have to pay currently to replace it.
  2. That $5K worth of refrigerant is held in place by a less-than-reliable $1 device that was invented in the late 1800s.

As an economist, I goggle at the mismatch.

But there appears to be nothing I can do about it.  Except to wait for the inevitable leak.

Now I’ll tell the story.  And try go get up to speed on modern refrigerant options.  And try to plan ahead.

My world and welcome to it.

My house came with an exceptionally quirky HVAC system.

The key elements are a pair of ground-source heat pumps.  That sounds pretty eco-friendly and high-tech, right?

As actually implemented, my home HVAC is a Rube Goldberg machine.  There’s a mile of plastic pipe buried in the back yard. Two pumps circulate water through that mile-long loop, terminating at two commercial (not home) AC compressors.  These grumble away in the basement, feeding refrigerant lines running to air handlers — the things that actually blow the hot or cold air around the house.  Those air handlers were clearly part of an earlier system, and to reach the one in the attic, the installers ran about 100′ of refrigerant lines outside, up the side of the house, and over top of the roof.  The whole mess is controlled by a mix of wired and wireless thermostats of dubious reliability.  These, in turn, interface with the 65-year-old three-zone baseboard hot water heat via a high-tech high-efficiency gas furnace and electronic interface, that actually turns the hot water baseboards on and off via valves than run on melted wax.  (That’s not sarcasm, that’s a Taco (pr. Tay-co) valve.)

I mean, what could possibly go wrong?

In any case, we fired up the heat pumps this past weekend, only to find that one of the two heat pumps wasn’t.  Pumping heat, that is.

A service call later, and the diagnosis is that the unit is drastically low on refrigerant. 

Normally, that’s not much of an issue.  Find the leak, fix it, and refill the system.

But in this case, it’s a problem.  That’s because the bozos who installed those heat pumps less than 20 years ago cheaped out and installed units that use R-22 refrigerant, also known as Freon.  Of ozone destruction fame. That can no longer be made in the U.S. or imported into the U.S. 

(At the time they installed these, it was already well known that Freon was on its way out.  When I replaced the AC in my prior house, years before, I opted for the newer “Puron” (R410-A) refrigerant.  Buying a new R-22 unit at that time would have been foolish.  But now I own two of them.)

Normally, that’s not much of an issue either.  There are now drop-in replacement refrigerants like R-421A.  These don’t destroy the ozone layer, and in most cases you can simply vacuum out the R-22, replace with R-421A (or similar), and get on with your life.  (They have a huge global warming potential, though, as discussed below.)

But in this case, it’s a problem.  Apparently those replacements won’t work in every system.  My HVAC guy assures me that mine is one such.  Maybe the 100′ long refrigerant lines have something to do with that.  Maybe it’s the fact that these are oddball commercial units, not home units.

So in my case, the options were to fix the leak and top up the leaking unit with R-22, or throw it away and get a new one.  Which, owing to the unique setup, is almost certainly going to cost a mint.  Assuming my HVAC guy is giving me the straight story.

So I had my HVAC guy repair the leak and top up the system.  Which is when I found out that this company now charges more than $300 a pound for R-22.  I expected it to be expensive — that’s been in the works since 2010, when the decision was made to phase it out in the U.S.   Which means my replacement cost for the 14+ pounds of R-22 in my two units is somewhere around $5000.

(But I didn’t expect it to cost me more than $300 a pound, but it was a decision that I made on the fly.  I now see that the wholesale price of R-22 is around $40 a pound.  As shown below.   So my HVAC guy apparently took a roughly 800 percent markup.  Because, hey, my system wasn’t going to run without that additional R-22.  So they got me.  But this definitely means I’m looking for a new HVAC firm.  And I’m also wondering whether I got the straight scoop regarding whether or not drop-in replacement refrigerants will work.)

 

 

And what caused the leak, for which I had to purchase about $1500 worth of R-22?  That was due to a faulty Schrader valve.  Which is a roughly 70 cent part, using a design patented in 1893.

And that’s just the way it is.  The valves that made sense when they were holding in the (then) $1 a pound Freon are now are all that stands between the atmosphere and my precious antique R-22.

Looking ahead.

Given the dollars involved, I probably ought to think through what my next steps are.  As opposed to panic-purchasing something the next time there’s a problem.

There are a lot of considerations.

Source:  US EPA

First, with no new production or import allowed in the U.S., at the current price, it’s a pretty good bet that R-22 is now a zero-sum game.  That is, everything currently residing in appliances will get reclaimed and re-used, until it all eventually leaks into the atmosphere.

(In theory, per the EPA, you can ship your R-22 off to have it destroyed at a certified destruction facility.  Or you can plan on storing it safely, indefinitely.  But I don’t see that happening if you can re-sell it to your customers at $300+ a pound.

This means there is no environmentally benign way to get rid of the R-22 that came with my house.  If I opt for new equipment, the HVAC techs will, by law, recover (pump out) all the R-22  in the current system.  But surely they’ll sell that to be reclaimed and re-used.  Which means that it will be used in somebody else’s leaky system.  And one way or the other, it’s going to end up in the atmosphere.

I should mention here that in addition to R-22’s destruction of the ozone layer, all these refrigerants — even the ozone-benign ones — have a horrifically high global warming potential (GWP).  R-22 isn’t the worst, but it’s bad enough, with a 100-year GWP of 1850 (reference).  Or, in other words, a pound of that stuff has as much impact as 1850 pounds of C02.  My little R-22 leak had as much global warming impact as releasing about four tons of C02.  That’s about the same global warming impact as an entire year’s worth of electricity use, in my house.

I think that gives me my first and most obvious decision point:  As long as my current heat pumps don’t leak, I should make every effort to keep them running.  Even though the equipment is old, it’s still a reasonably efficient heating and cooling plant because it’s a ground-source system.  I don’t think any marginal efficiency improvements from new equipment could plausibly offset the GWP from the earlier-than-necessary release of my 14 pounds of R-22.

The fact that I own this R-22 is nothing for me to feel guilty about.  I’m not the one who installed the R-22 heat pumps.  But now, I’m the custodian of it.  It’s on me to address any leaks, to try to keep this crap bottled up for as long as possible.

Conversely, as soon as a unit develops an irreparable leak, I should decommission it.  With one caveat.  My HVAC guy actually gave me the option of just refilling the system, and not bothering to find the leak.  With a slow leak, plausibly I could have kept this running for years on maybe a pound of R-22 per year.  But if I could not fix the leak, it would be better that the R-22 go into somebody else’s system, with the chance that it doesn’t leak, than to keep it in a known leaky system.

(And so, that’s the first benefit of thinking this through.  Because, had this occurred in some sort of emergency situation, such as a deep cold snap, I’d probably have opted to keep the system running at all costs.  Now I have my head screwed on straight regarding the environmentally sound(er) thing to do.)

The caveat is that the systems you can get today all use refrigerants with high global warming potential.  So much so that refrigerants that were cutting-edge replacements for R-22 twenty years ago are themselves now being phased out.  Puron (R410-A), for example, has a GWP of more than 2000.  It came on the market in 1996, and it’s slated to be phased out sometime in the 2030s.

So the caveat boils down to this:  If we’re only a year or two away from new units that use a truly benign refrigerant (no ozone destruction, minimal GWP), it might make sense to limp along for that year or two, rather than install new equipment with soon-to-be-outdated refrigerant.

Right now, as I read it, the world of low-GWP refrigerants is in flux.  For heat pumps, Carrier now makes a large commercial ground-source unit using R-1234ze, with claimed GWP of less than 1 (reference).  Looks like some other manufacturers are jumping on that bandwagon.  So, plausibly, if that trend continues and they enter the home heating and cooling market, by the time I have to replace these old R-22 ground-source heat pumps, I ought to have a fairly efficient and environmentally benign alternative.

In the meantime.

Meanwhile, I remain appalled that the same century-old tech that keeps my car tires inflated is all that stands between my precious R-22 and the outside world.  When my HVAC guy comes back for a routine maintenance visit in the spring, I’ll be grilling him about options for making sure I never get another Schrader valve leak on these systems.  Maybe I can have him replace those prophylactically (there are tools for replacing them with out losing the R-22).  Maybe it’s a question of putting gas-tight caps over them.

One way or the other, there has to be a more secure way to keep this particular genie in the bottle.  The valves that made sense 20 years ago seem ridiculously out of place for a gas that’s going for hundreds of dollars a pound.

Post #1636: Countertop water filtration.

 

This is my overview of simple (no-plumbing) water filtration systems currently on the market.  As with many of my posts, I’m writing this up to make sure I understand the topic.  I doubt anyone will read the detail.

To cut to the chase, after 20 years, we’re abandoning our standard Brita water filter in favor of the upgraded version, the Brita Elite.  The new Brita filter fits the old pitchers, but appears to do a much better job at filtration.

This, while I continue to look over our options for a more sophisticated filtration system.

In brief:

Continue reading Post #1636: Countertop water filtration.

Post #1635: First frost

 

Source:  Analysis of historical weather data from NOAA.

Stealth frost

It looks like we’re going to have a few nights with freezing temperatures this week, here in Vienna, VA.

I’ve been doing a few chores in and around the garden to get ready for that.  The most important of which was moving a large potted lime tree into the garage.  Even a touch of frost and that would likely die back to the ground.  I’ve also drained all the water barrels, and I’m bringing hose timers and other frost-sensitive objects inside.

This means it’s also time to redo my prior analysis of trends in first frost.  It’s been unseasonably warm in the East, so it would be no surprise if this year’s first frost were a bit later than usual.

But when I actually looked at the data, I got a surprise:  Dulles Airport (my standard for this frost analysis) recorded a frost about three weeks ago, on October 21.  I missed that, and clearly we didn’t get a frost in Vienna, based on (e.g.) the fact that my okra plants are still alive.

That said, on average, first frost in my area is now about 20 days later than it was in the 1960s.  As you can probably see from the graph, virtually all that change has been in this century.  That couple-of-weeks shift in the first frost date appears to be a fairly widespread phenomenon (per this reference).

That’s consistent with the continued northward shift of the USDA hardiness zones.  They update those every so often, using more recent historical weather (i.e.) climate data.  With the most recent up date (2012, using the 30 years of weather ending 2010), most of the zone boundaries slid north, compared to the prior map (using the 30 years ending in 1990).  Apparently, the average rate of travel of the hardiness zone boundaries is reported at 13 miles (north) per decade (per that same reference).  That varies widely, as zone boundaries at the coast shift more slowly, due to the moderating effects of ocean temperatures.

In any case, it will be sometime around 2040 before Vienna, VA makes it into Zone 8 — or Zone 8 makes it to Vienna — take your pick.

Source:  NOAA, via the New York Times 

So I guess it’s still a bit early to expect climate change to save me from these frost-related chores.  But give it enough time, and we our descendants our descendants, if any, will have no problem growing palm trees around here.

As was true at last year’s first frost date (Post G21-057), indoor relative humidity remains high.  That said, I’m keeping an eye on it, and when it drops below 40%, I’ll start running my humidifiers.  I summarized why that’s important for prevention of respiratory infections in Post #894.

Source:  American Society of Heating, Refrigerating and Air-Conditioning Engineers

Post #1629: Worst economic advice ever?

 

What is wrong with this picture?

This is a political ad that has aired repeatedly in the past few weeks in the Washington, DC area.  It’s an ad for a candidate for U.S. Representative from one of the Virginia suburban districts.

That’s the candidate and her father.

Have you figured out what’s wrong?

Sure, this is a campaign ad.  You’re supposed to respond to the images emotionally.  You aren’t supposed to think about what they are actually saying.  But instead of just basking in the warm glow of that aw-shucks fiscal conservatism, try actually reading the words. 

Crudely put, savings + spending = income.  Which means that the candidate is endorsing the notion of spending less than 50% of one’s income.  As a matter of logic, that’s the only way that you can save more than you spend.

Let me walk through the implications of that, one step at a time.

Microeconomics:  Not feasible for the middle class.

Source:  Federal Reserve Bank of St. Louis (FRED) system.

OK, let’s just take that at face value.  The printed advice above boils down to “you should save at least half of your income”.

First, to be clear, for the U.S. as a whole, that’s never happened and never will.  Above you can see more than a half-century of the U.S. personal savings rate.  It has typically ranged from 5% to 15%, with a secular trend toward less savings.  In recent years, 5% would be roughly normal.

But that doesn’t tell the full story.  Almost all that savings is done by the well-to-do.  The top 10% and top 1% of earners. Here’s a graph — of unknown quality — of savings rates by wealth.

Source:  financialsamurai.com

That looks about right to me.

For the vast majority of Americans, the idea of saving half your income is absurd.  It’ll never happen, for the simple reason that you need to pay the bills. 

Even more absurdly, this same candidate has made much of how middle-class families must struggle to make ends meet. So the message here is that the middle class is struggling, but it should be saving more than half of its current income.

So, look, if you make tons of money, sure, you can look down on the great unwashed masses and their pitiful savings rates.  I’ve had years where my little business was so successful that I did, literally, save more than I spent.  But I can also recall the single-digit checking account balances of my youth.  So if people with modest incomes don’t save much money — and they never have — I find it hard to fault them.  Personally, I’ve always been extremely financially conservative.  But I don’t think that somebody with two minimum-wage jobs should be expected to save half their income.

Macroeconomics:  Economic suicide.

It goes without saying that if, in some imaginary world, Americans suddenly decided to save half their income, the economy would immediately tank.  We’d have the next Great Depression.

Oh, wait, didn’t that just happen?  The top graph below is personal savings, which appears to have hit nearly 35% recently.  The bottom graph is the unemployment rate, which hit 15%.  That was, in fact, the highest unemployment rate since the Great Depression.  Which we just had, during the pandemic.

Source:  Federal Reserve Bank of St. Louis FRED system.  I should note that this is a bit of a cheat, on the savings side, because individuals largely saved their first round or two of COVID-19 payments.  (Which is why they needed additional rounds of stimulus, get it?)  That artificially gooses the observed savings rate, but only by a bit.  Basically, from the standpoint of economics, people were pretty much panicking, as they had during the Great Depression.  And as everyone individually reduced spending, the macroeconomic results were inevitable.

My first point being that if Americans were suddenly to follow that folksy bit of economic wisdom, that would guarantee that we’d have the next great depression.

So, why didn’t we slide into an economic depression?

The answer is the COVID-19 spending bill that Trump signed.  Followed by the two COVID-19 spending bills that Biden signed.  All of which force-fed money to U.S. corporations and citizens, to counteract the collapse of demand that occurred during the pandemic.

Which was matched by similar programs undertaken by all of the industrialized nations.  This wasn’t a U.S. idea.  This is what everybody with any sense did.

Anyway, all that money is now coming out of people’s savings, and going into spending.  That’s my interpretation of why the U.S. personal savings rate is now just about 3%, which is low compared to recent history.  It’s also why the unemployment rate is about 3.5%, also low by recent history.  And, to some significant extent, why prices are up.

It may seem like the Federal government spent a lot of money to keep the COVID economic crisis from snowballing.  We did, in fact, run the largest deficit (as % of GDP) since WWII.

But the point is, that was almost undoubtedly cheaper than having the next Great Depression.  Which is what the entire industrialized world was facing.  Which is why everybody threw money at their economies.  They didn’t do it because they were stupid.  They did it because it was smart.  It was cheaper than the alternative.

Are we living with the consequences now?  Yep, sure are.  Are people going to squabble about how much was spent, try to use it to political advantage?  Yep, sure are.  Will folks forget why the money got spent in the first place?  No doubt.

Will this candidate ever get called to task for suggesting that middle-class people ought to save more than half of their income?  Nah, I bet nobody even noticed what that ad implied.  Will anyone ever point out that uniform adoption of that policy is collective economic suicide?  For sure not.

That’s just the way the world works.  Please feel free to say anything, no matter how stupid, as long is riles up the right people.  And never, ever apply logical analysis to anything that is said.

Don’t worry, be happy.

Post #1624: 80 MPG?

 

Not quite.  But I think I’m finally figuring out how to drive my wife’s Prius Prime.

Above is the gas mileage on my wife’s Prius Prime, after a round trip from Vienna VA to Harper’s Ferry WV.  This is all after resetting the odometer once the battery was depleted.  So it’s straight-up gas mileage.

This trip contained a short section of high-speed driving, but was mostly hilly primary and secondary roads in western Virginia and West Virginia.  And I think I finally understand how I’m getting such great mileage.

The Prius Prime loves hilly roads.  It is an excellent car for a particular style of pulse-and-glide driving.

Continue reading Post #1624: 80 MPG?

Post #1618: There ain’t no disputin’ Sir Isaac Newton: Efficient driving in an EV.



Driving an electric vehicle (EV) efficiently is forcing me to learn some new driving habits.  And, in particular, I have to un-learn some cherished techniques used for driving a gas-powered car efficiently.


When I look for advice on driving an EV efficiently, all I get is a rehash of standard advice for driving a gas car.  But the more I ponder it, and the more I pay attention to the instrumentation on my wife’s Prius Prime, the more I’m convinced that’s basically wrong.


An electric motor is fundamentally different from a gas engine.  With an electric motor, you want to avoid turning your electricity into heat, rather than motion.  That boils down to avoiding “ohmic heating”, also known as I-squared-R losses.


To minimize those heating losses, you want to accomplish any given task using or generating constant power.  That task might be getting up to speed after stopping at a red light, or coming to a stop for a red light, in some given length of roadway.


Here’s the weird thing.  Assuming I have that right — assuming that an efficient EV driving style focuses on providing or generating constant power over the course of an acceleration or deceleration — that implies a completely different driving style, compared to what is recommended for efficient driving of a gas-powered vehicle.


In particular, the standard advice for gas cars boils down to accelerating and decelerating with constant force.  When you take off from a stop light, aim for a constant moderate rate of acceleration.  When you are coming to a stop, aim for a steady rate of deceleration.  Constant acceleration or deceleration boils down to constant force on the wheels, courtesy of Sir Isaac Newton’s F = MA (force is mass times acceleration).


But power is not force.  As I show briefly, in the next section.  In a car, power depends on speed.  Constant force on the brake pedal (and so, on the brake rotors in a traditional car) generates far more power at high speed than at low speed.  Similarly, a constant rate of acceleration consumes more power at high speed than at low speed.


And so, there seems to be a fundamental conflict between the way I was taught to drive a gas car efficiently, and what seems to be the right way to drive an EV efficiently.


In a nutshell, to drive an EV efficiently, you should be more of a lead-footed driver at low speeds.  And taper off as the car speeds up.   Conversely, hit the brakes lightly at high speed.  And press the brakes harder as the car slows.


That’s the driving style that aims for production and consumption of power at a constant rate, over the length of each acceleration or deceleration. And that’s completely contrary to the way I was taught to drive a gas vehicle.


Think of it this way.  Suppose you apply a certain level of force to the brake pedal of a traditional car.  The resulting friction between brake pads and rotors will generate heat.  That rate of heat production is, by definition, power, as physicists define it.  You’re going to generate a lot more heat per second at 80 MPH than you are at 4 MPH.  (In fact, 20 times as much.)  Restated, for a given level of force, you are bleeding a lot more power off the car’s momentum at 80 MPH than at 4 MPH.  And those big differences in power, over the course of an acceleration or deceleration, are exactly what you want to avoid in an EV with regenerative braking, in order to avoid I-squared-R losses.


 




Force and power:  A brief bit of physics and algebra




1:  Two definitions or laws of physics


Work = Force x Distance


Power = Work/Time


2:  A bit of algebra


Substitute for the definition of work:


Power = (Force x Distance) / Time.


Re-arrange the terms:


Power = Force x (Distance/Time)


Distance/time = speed (definition)


Power = Force x speed.


For a constant level of force applied to or removed from the wheels, the rate of power consumption (or production) is proportional to the speed.


Upshot:  To accelerate or decelerate at constant power, the slower you are going, the heavier your foot should be.  The faster your are going, the lighter your foot should be.  For the gas pedal and the brake pedal.




Ohmic heating:  Why a long, hard acceleration trashes your battery reserve.




Anyone who drives a PHEV — with a relatively small battery — will eventually notice that one long, hard acceleration will consume a big chunk of your battery capacity.  On a drive where you might lose one percent of battery charge every few minutes, you can knock several percent off in ten seconds if you floor it.


Another way to say that is that getting from A to B by flooring it, then coasting, consumes much more electricity than just gradually getting the car up to speed.


I’m not exactly sure why that is.  But I am sure that it is universally attributed to I-squared-R or ohmic heating losses in the motors, batteries, and cables.


Any time you pass electric current through a wire or other substance, it heats it up.  From the standpoint of moving your car, that heating is a loss of efficiency.  The more current you pass, the more it heats up the wire.  And that heating is non-linear.  Watts of heat loss are proportional to I-squared-R, in the argot.  They go up with the square of the current that you pass through that wire.


Again, I’m not completely sure here, but my takeaway is that your heating losses, at very high power, are hugely disproportionate to your losses at low power.  At constant voltage, I believe those losses increase with the square of the power being produced by the electric motors.  In other words, ten times the power produced to move the car creates 100 times the ohmic heating losses.


And that’s how ten seconds of pedal-to-the-metal can use up as much electricity as 10 minutes of moderate driving.


That said, I have to admit that I’m relying on “what everybody says” for this.  For sure, hard acceleration seems to trash your battery capacity far in excess of the distance that you travel at that rate of acceleration.   Whether the root cause for that is I-squared-R losses, or something else about the car, I couldn’t say.


Either way, my takeaway is that if losses are proportional to the square of power consumed or generated, then to accomplish any given task (any fixed acceleration or deceleration episode), your aim should be to do that at constant power.  Because that’s what will minimize the overall energy loss from that acceleration or deceleration episode.




Drive like you are pressing on an egg — that was a real thing.  EV drivers should chuck the egg.




Source:  Duke University Libraries, via Internet Archive.


Those of us who grew up during the 1970s Energy Crisis will probably recall public service announcements that asked you to drive as if there were a raw egg between your foot and the gas pedal.  I managed to find a Texaco ad of roughly that era, laying out that egg-on-gas-pedal meme.  The picture above is from that video.


As kids, that was pretty much beaten into us.  Responsible driving means no jackrabbit starts, no tire-smoking stops.  Easy does it.  We’re in the middle of a prolonged gasoline shortage, after all.


So now I come to the part that is absolute heresy for someone of my generation.  If you’ve absorbed the prior two sections, you realize that this advice probably isn’t correct for an EV.  Why?  To consume power at a constant rate over the course of an acceleration, you should start off with a brisk rate of acceleration, then diminish that as the car speeds up.


In other words, if you drive an EV, drive with a lead foot.  Not all the time.  But at the start of every acceleration.  And the end of every deceleration.


If you drive an EV, chuck the egg.




The Prius Prime Eco display




Source:  Underlying picture is from Priuschat.


With that understanding in hand, I’m finally starting to make some sense of the “eco” display on my wife’s Prius Prime.


In theory, this little gauge is giving you guidance on how to drive the car most efficiently.  In practice, I could never make head or tail out of it, except that it seemed to be telling me to drive with a lead foot.


Which, I now understand, it was.


On this display, if you put your foot on the gas, it will show you your actual throttle (gas pedal) position, and the gas pedal position that will, in theory, give you greatest efficiency.


By contrast, when you put your foot on the brake, it doesn’t show you the brake pedal position.  Near as I can tell, it shows you the amount of power than you are generating.  That is, a constant brake pedal position will lead to a shrinking bar, as the car slows down and less energy is generated.


Watch what happens if I try to accelerate gently:




It’s possible that all the meter is actually telling me is that a very lightly-loaded electric motor will operate inefficiently.  I don’t think the Prius eco monitor is actually trying to get me to drive at constant power.


Edit 3/11/2024:  After driving around with a ScanGauge III, my conclusion is that accelerating at constant power is exactly what the eco-meter is trying to get you to do.  It wants you to start off with a heavy foot, and then, as you accelerate, it wants you to back off.  Near as I can tell, that bar is set up to keep you at around 23 HP of power output, or 50 amps of discharge current, or a “2 C” rate of discharge, for this battery.


In particular, my diagram above is labeled wrong. The two red arrows should be labeled “desired power output” and “actual power output”.  You will notice that if you don’t move the gas pedal, the “actual power output” line will creep up as you speed up.  The only way to keep that line in the same place is to back off the gas as your speed increases.  So that line isn’t the throttle position, it’s the power output (power = force x speed).


But no matter how I arrive at it — from theory, or from finally paying full attention to the Prius eco meter — the whole drive-like-there’s-an-egg-between-foot-and-gas-pedal is clearly obsolete.  Gentle acceleration may get you your best mileage in a gas-powered vehicle.  But it’s not the correct way to drive an EV.



	


	
	






	
	

		
Post #1617:  When will the tear-down boom end, the sequel.
	


	

		
 


It hasn’t been possible to buy a small house in Vienna, VA for at least a decade now.   Every small house that goes up for sale is purchased by developers, who then proceed to tear it down and build the largest house that will fit onto that lot.


This sustained destruction of middle-class housing, replacing it with lot-filling McMansions, is what I have termed “the tear-down boom”.


I have written about the various implications of the tear-down boom.  Among other things, this continual replacement of small houses with gigantic houses means that:


    

  • Post #519.  Town revenues from residential real estate have been pushed materially higher by the resulting increase in the price of the houses.
    • 

  • Post #308.  There’s a tremendous mis-match between the stock of houses in the Town of Vienna, and the houses available for sale.  Middle-class people can live here — if they already own a house — but they can’t move here, because all the middle-class houses are replaced with McMansions before being re-sold.  As a result, increasingly, Vienna is a town for the wealthy, not the middle class, something I termed the “Mcleanification” of Vienna.
    • 



And yet, some of the economics of the tear-down boom just didn’t seem to make a lot of sense, simply as way to generate housing stock.  People really don’t need 10,000 square foot houses, and everything I read about the next Gen X and later is that they have no interest in buying such gigantic pieces of real estate.  Seemed like a classic case of “sell it to whom?”.


The best explanation I could give for the tear-down boom is that it was the result of two toxic Federal economic policies.  These were the huge tax advantages to home ownership, including both tax sheltering of current income and tax-exemption of any capital gains, and near-zero real (inflation-adjusted) interest rates.   In 1997, the Federal government eliminated capital gains on housing.  (With some limits.)  That was on top of the tax sheltering that housing provides via income-tax deductibility of mortgage interest and property taxes.  Then, in 2008, the Fed dropped inflation-adjusted interest rates to zero or below, following the near-collapse of the U.S. financial system.


Between those two policies — the tax advantages and the free money — it became ludicrously cheap to finance the purchase of a mega-home.  And that mega-home was a highly-leveraged investment that was, ultimately, better than tax-free.


But trees don’t grow to the sky.  Back in 2019, I asked “When will the tear-down boom end?”  That was Post #217.


Even then, the market was showing some oddities.  Oddity #1 is that these mega-homes were appreciating less rapidly than adjacent lower-priced homes.  Oddity #2 is that the changes in tax law in 2018 made it much more expensive to own homes costing over about $850,000.  Here’s the analysis of just how much more expensive it became to carry the cost of a $1.4M house after the 2018 changes in Federal tax law:




Not only did it suddenly cost a lot more to carry that $1.4M house, almost all of the additional cost came from the housing value just in excess of $850,000.  Basically, the law reduced the size of what I would term the “tax efficient” house, that is, the house that earns you the maximum tax breaks as a percent of cost.




As a result, in 2019, I looked at that and said, isn’t this going to put the brakes on the tear-down boom?  


And so far, the answer is no.  Just casually driving around town, these still seems to be a tear-down on pretty much every block.


So far.




Today’s mortgage interest rates.


In this last section, all I want to do is assess the impact of the rise in mortgage interest rates.  Literally, dig up the spreadsheet above, and replace the then-current 4% mortgage interest rate with the current 7% (or so) rate.




Source:  Federal Reserve Bank of St. Louis (FRED) system.


Redoing the analysis, I find that the carrying cost of a $1.4M (small) McMansion in Vienna is now about 50% higher then it was back in 2018.  And 86% higher than it was in 2017, before they changed Federal tax law to reduce the tax advantages of owning an expensive home.




So, to be clear:  Those houses are still big money-makers for the owners, as housing prices have risen steeply in the past year.  That said, if home prices merely stabilize, new McMansions will have after-tax carrying costs in today’s environment that are 86% higher than they were in 2017.


My belief is that this plausibly is going to put a damper on tear-downs in Vienna.


I’ve been wrong about that before.


But I believe it strongly enough that I spent last week painting the front of my house.   That’s a real change for me, because I had simply stopped doing any maintenance on my house that didn’t directly affect occupant health and safety.  I figured, why bother to keep the place up, when they’re just going to tear it down when I eventually move?


I was letting the house deteriorate, peeling paint and all.  But now I have about a decade’s worth of deferred basic maintenance to do. Because in today’s environment, it’s no longer a given, I think, that this house will be torn down when I leave it.