Anything that I have tested empirically, or explain with detailed calculations, or just generally bother to get all the facts straight.
This is part of an ongoing series to test various internet-based suggestions for extending the life of a razor blade. You can see the background for this in the Post #1672.
I suppose that any group of people obsessed with the minutia of some activity will seem a bit odd to the rest of us. But the more I dive into on-line shaving culture, and on-line blade-sharpening culture, the weirder it gets.
Continue reading Post #1677: Planning the rest of my razor blade experiment.
This is part of an ongoing series to test various internet-based suggestions for extending the life of a razor blade. You can see the background for this in the just-prior post. Continue reading Post #1673: Stropping a used razor blade. Meh.
Six years ago I decided to start using an old-fashioned (“double edged”) safety razor.
I got a couple of “blade samplers” from Amazon — collections of maybe a dozen different brands, five blades from each brand. I then bought a 100-count box of Persona blades. They got good reviews and, at that time, they were made in Virginia.
Sometime this year, I’ll probably have to buy razor blades again. So, obviously, we’re not talking about a huge per-diem expenditure, for shaving. Nevertheless, whatever I buy this time, I’m going to end up living with it for years. So I’ve been revisiting the market for double-edge razor blades. And, incidentally, disposable razors. Continue reading Post #1672: Does anything really extend the life of a razor blade? Part 1, the setup.
Source: American Society of Heating, Refrigerating and Air-Conditioning Engineers. This is from the 2016 ASHRAE Handbook—HVAC Systems and Equipment (SI), Chapter 22: Humidifiers.
I’m a big believer in running a humidifier or two during the coldest part of the winter. I harped on that point just recently, in Post #1640. I do it as much for the health benefits (illustrated above) as for the comfort.
That said, I realize that I pay a considerable energy penalty for doing that.
Interestingly, a lot of people do not seem to understand just how large that energy cost is. Here’s the trick: You can’t measure it by the amount of electricity the humidifier itself uses. If you have anything other than a boiling-water humidifier, by far, the majority of energy used to run your humidifier comes from your home furnace.
Which I shall now demonstrate, and briefly calculate.
First, this ain’t rocket science. Everybody knows that evaporating water cools things off. For this next part, you just have to get your mind around what, exactly, is being cooled off by the evaporation from your humidifier. And then, what you have to do about that, in the wintertime.
In the case of an evaporative humidifier, what is being cooled is the air inside your house. The humidifier literally absorbs heat from room air. You can easily prove that to yourself, as I did above. My Vornado humidifier cools down the room air by about 5 degrees when used on its medium setting.
That’s just physics, and there’s no getting around it. No matter how you do it, converting liquid water into water vapor takes a lot of energy input. Boil it, evaporate it from a humidifier pad, mist it into the air and let those tiny drops evaporate. Or just hang your damp laundry inside. If you start with liquid water, and end with water vapor, somewhere along the way, that water absorbed a lot of heat energy. From somewhere.
At room temperature, it takes just about 700 watt-hours of energy to evaporate a kilogram of water (reference). Which means that evaporating a U.S. gallon of water, at room temperature, requires somewhere around 2.5 kilowatt-hours of energy (or about 8500 BTUs).
And so, per the illustration above, if I want keep the room at 68F, I’m going to have to run my furnace to make up for the 5-degree difference between room temperature and the cool air coming out of the humidifier. How much energy will my furnace have to supply? Just about exactly 8500 BTUs for every gallon of water I evaporate. Or, if I do a typical 2-gallon day, roughly 17000 BTUs or 5 KWH of energy, per day, will have to be added into the room air, that would otherwise not have to be supplied.
That works out to a rate of power consumption of (5000 W-H/24 H =) about 200 watts, averaged over the course of a 24-hour, 2-gallon day. By contrast, the humidifier itself uses just 32 watts, run on medium speed. The upshot is that the furnace supplies roughly 85% of the energy required to run that humidifier, in a room with constant temperature.
The actual electricity use isn’t quite that bad, because my “furnace” is a heat pump with a coefficient-of-performance (COP) of roughly 3. That is, it releases about 3 watts of heat energy inside my home, for every watt of electricity consumed. So it only uses electricity at a rate of about 70 watts, on average, to offset the cooling produced by the evaporative humidifier.
Answer: Not much.
To drive this home, let me now compare the humidifier to a known household energy hog, the clothes dryer. A typical home dryer uses about 3.5 KWH per load. Here, if I ignore the COP advantage of the heat pump, my humidifier requires about 5.7 KWH of energy input per two gallons, including both the device itself (32 watts on medium), and the heat required to re-heat the air after it’s been cooled by evaporating water.
At which point, I’m hoping that a little light bulb goes off. Because those energy use figures are pretty close. Let me adjust them for the amount of water being evaporated.
Some time back, I figured that a typical load of laundry retained about 10 pounds of water (Post #910). So that’s about 3.5 KWH of electricity, to evaporate 10 pounds of water, in a dryer. But two gallons of water per day, out of an humidifier, is about 16.5 pounds of water. So, at the rate my dryer uses energy, that ought to take about (16.5/10 x 3.5 KWH =) 5.8 KWH of energy.
In other words, per pound of water, your home humidifier uses just about exactly as much energy as your home clothes dryer.
Because, of course it does. It has to. Plus or minus a bit of wasted heat, your home clothes dryer does exactly the same thing as your humidifier. It’s taking water and converting it to water vapor. It just does it at a different temperature.
The only energy advantage my humidifier has over my clothes dryer is that the humidifier uses a more efficient heat source. The COP 3 heat pump uses less electricity, per unit of heat, than the resistance heating elements in the dryer. So the actual electricity use is lower, due to the magic of heat pumps. (Plausibly, if you had one of the new heat-pump clothes dryers, there wouldn’t be much difference at all.)
Finally, if you have achieved enlightenment in this area, you now realize that hanging your laundry to dry, inside, in the winter, does not save anywhere nearly as much energy as you probably thought it did. Sure, you don’t run the dryer. But you run your furnace instead. That’s to make up for the cooling effect all that wet laundry has on your room temperature. Which is exactly the same cooling effect that the humidifier has.
There ain’t no such thing as a free lunch.
Hang on, Mr. Conservation-of-Energy. You’re saying that the humidifier is, in effect, withdrawing heat out of the room air? Where does that heat go?
These devices:
all work by converting “sensible” heat — that is, air temperature –– into “latent” heat — that is, the energy embodied in water vapor as opposed to liquid water.
The energy is still there. It was neither created nor destroyed. It’s simply in a different form. In this case, it’s in the form of the energy that’s in the water vapor, as opposed to liquid water. If you could condense that water vapor back into water, it would release exactly the amount of energy it absorbed in making the transition from liquid water to water vapor.
And, as night follows day, any time you convert liquid water into water vapor, that’s going to absorb heat energy. In all of the above, the heat comes out of the air, and the air cools down. For most of these devices, that’s the entire point. For humidifiers, by contrast, that’s a regrettable downside.
My point being, physics doesn’t care about your opinion. If you like street-fair cooling stations, or patio misters, because they cool you off — up to a claimed 30 F in ideal conditions (reference) — then, logically, you have to realize that your home humidifier is also cooling you off. In the dead of winter, when that’s the last thing you need.
And that’s why running your humidifier, in the winter, takes just about as much energy as running your clothes dryer. Per pound of water, that is. From a physics standpoint, there’s not much difference between the two appliances. One of them heats up air, and converts water to water vapor. The other one converts water to water vapor, which then requires you to heat up the air. The only difference is the timing, and the efficiency of your home heating system compared to the simple resistance heaters (hot wires) used in a typical clothes dryer.
For some people, cold winter weather brings thoughts of hot chocolate by the fireplace, cozy comforters, or maybe skiing.
By contrast, I find myself thinking about insulation and R-values.
So, in the spirit of the holidays, here are two R-value calculations that I’ve been meaning to make.
Whenever the weather turns cold, I start getting lots of hits on Post #1412, on making an electrically-heated cover for outdoor faucets. Of late, I’ve been getting more than a hundred hits a day, thanks to this recent cold snap and an offhand reference in an on-line forum for Texas Aggies fans.
One of the interesting findings was how little electricity it takes to keep the inside of the faucet protector warm. For example, a mere 4 watt night-light bulb raised the interior temperature by 28 degrees. That more than meets my needs in any cold snap likely to occur in my area.
But is it really plausible that 4 watts could do that? Or was I (e.g.) mistaking heat leaking out of house for the impact of that small electric light?
Obviously, I could check that empirically by hanging up a standard faucet cover with no added heat, and seeing what the interior temperature was. But, at present, it’s about 15F outside, so I’m ruling that out for now.
Instead, this is a classic cases of “Sure, it works in practice. But does it work in theory?” I’m going to do a theoretical calculation of the temperature rise I should expect, using the R-value (insulating value) of Styrofoam, the dimensions of that faucet cover, and the energy output of a 4-watt bulb.
I’m going to model this as a Styrofoam box with dimensions 4.5″ x 4.5″ x 6″. That effectively covers the open face of the faucet cover with Styrofoam, instead of (in my case) brick. So I’m expecting to see more than 28F temperature increase out of this calculation. The box walls appear to be about 5/8″ thick.
Two final bits of data. The R-value of Styrofoam is listed by most sources as around 5.0 per inch. And 4 watts is equivalent to about 13.5 BTUs per hour (BTUH). (I rounded that down a bit to account for the small amount of energy that escapes from that bulb in the form of light, rather than heat.)
Here’s the calculation, first assuming foam on all sides, and then accounting for one side being brick, with a total R-value (for two inches of brick) of 0.88. (I don’t show the full detail of the brick calculation, only the bottom-line average insulating value of the combined foam/brick container.)
The upshot is that this does, in fact, work in theory. The theoretical temperature rise I get from an all-foam box is 41F, much more than I observed. The theoretical rise I get if I replace one side of the box with brick is 28F, exactly what I observed.
It’s purely a matter of chance that this calculation hits the observed value exactly. The fact that it’s close shows that what worked in practice, does, in fact, work in theory.
I’ve been watching Engels Coach Shop on YouTube for some time now. The proprietor is a self-employed wheelwright whose long-standing business builds and fixes all manner of horse-drawn transportation.
This has absolutely no practical relevance to my life, but is purely a pleasure to watch. Not only for the actual work performed, but also because the guy knows how to film, edit, and narrate a video.
Of late, he installed a 3000-gallon above-ground tank for watering his cattle. To which you might reasonably say, so what? Until you realize that he’s in Joliet, Montana. To put it mildly, the combination of an above-ground water tank and a Montana winter constitutes a freeze risk.
On the one hand, it’s heavily insulated (reported R50 on the sides, R120 on the top), and the water itself stores considerable heat energy.
On the other hand, it’s in the middle of Montana.
Source: Western Regional Climate Center
Apparently his YouTube following is deeply divided on whether or not they think this will work. Mr. Engels seemed kind of amused at the folks who thought he was going to end up with a giant ice cube. For my own part, I’m guessing it will work just fine, based solely on the guy who built it. But I don’t quite grasp why he seems amused by the opposite opinion.
So rather than just guess, let me do a couple of crude calculations. From the standpoint of the arithmetic, it’s really no different from my faucet cover. Just bigger.
First, I wanted to check out the water tower in Joliet, MT. Just to be sure that a big enough tank, with enough throughput, would not freeze in that climate. But when I tried a trick that always works for finding water towers on the East Coast — use Google Earth, set the perspective flat, and look for a water tower to stick up above the houses, because they are all 120 feet tall, more-or-less — that didn’t work. This, despite the fact that there is a municipal water system with a 160,000 gallon tank.
That’s because the Joliet water tower is mostly underground. Like so. I have no idea whether that was driven by economics, or by threat of freezing.
Source: Laurel Outlook
So, is a well-insulated tank, above ground, a problem or not?
The first hint that it’s not a problem is that the total heat loss of this tank is maybe 16 times the heat loss of my faucet cover. This tank is enormously larger. But it’s also enormously better insulated. The combination of having about 300 times the surface area, and maybe 20 times the average insulation, is that, by calculation (below, highlighted in yellow), this tank only loses a bit over five BTUs per hour per degree F. That’s just 16 times the heat loss in my Styrofoam faucet cover.
Here, I’ve assumed a tank shaped like a cube, with an average R-value of 60 on all surfaces. Should be close enough for a rough cut like this:
Well, given that a four-watt bulb would heat my faucet cover, it should be no surprise that even a modest heat input would (eventually) result in a large temperature differential between the inside and outside of that tank. Where four watts was enough to create a 41F difference in my all-foam faucet cover, here, a typical stock tank heater (150 W) would (eventually) generate a massive 94F difference between interior and exterior of the tank.
That’s a big enough difference that (arguably) this simple linear R-value calculation does not exactly hold. I don’t think that much matters. If for no other reason that, given the tiny heat input (about the same as you would use to heat a cup of water to boiling for tea), it would take years to reach equilibrium.
(Well, might as well calculate that roughly. This is about 25,000 pound of water. To raise that by 94F, with zero losses, using a 150W heater, would take just over half a year. With losses, yeah, a couple of years. If then.)
I’m going to go out on a limb and say that, if the tank is well-mixed, running a 150W stock tank heater inside it would, in fact, guarantee that it would not freeze under almost any conceivable circumstances in that climate.
But there’s no electricity at that site. Instead, the tank has to “coast” all winter, using just the energy embodied in the water in the tank itself.
So, how much energy is there in that water? How much heat would you have to remove to take water, at a typical late-summer temperature for that area, and bring it down to 32F?
By definition, a BTU is the amount of energy required to raise one pound of water by 1 degree F. So if (say) the water starts out around 62F (late summer/early fall), it would have to lose over three-quarters of a million BTUs in order to reach 32F. As shown below, bottom line.
Now I’m going to do a little hypothetical calculation. Let me plop that tank down in January, in Joliet, MT, and see how much it cools off over the month. That is, let me start with that tank at 62F, and let it sit for 31 days with an average external temperature of 24F — the actual average temperature for that month and location. This should be a worst-case scenario for temperature loss, because it’s the largest temperature differential you could hope to see. Water temperature from late summer, against dead-of-winter air temperatures.
Here’s the simulation. I just calculate the daily heat loss, and then drop the temperature each day, using that heat loss (in BTUSs) as a fraction of the total heat embodied in the 62F vs 32F water. (That is, I pro-rate the BTUs of daily heat loss over the total 750K BTUs that would take the water from 62F to 32F).
OK, I finally get the joke. Worst case, this tank ought to lose just over 5F per month, in the coldest month of the year. And note that the cooler the tank gets, the slower the additional temperature loss gets. For all practical purposes, the likelihood that the tank will freeze is zero.
(Note that the calculation is linear in temperature, so that it doesn’t really matter if the temperature does up and down in January. The average heat loss is going to match the average temperature. There are more refined physics calculations that will add some slight non-linearity to this, but not enough to matter).
Unsurprisingly, this tank isn’t just built for that climate. It’s over-built. Some of my assumptions might be a bit off. The tank is a cylinder, not a cube. Likely I could have calculated the average insulation value better. I don’t really know the insulation value for the bottom of the tank. And so on. But even with that, this seems to have been built with a huge margin of safety.
I should have expected no less.
With all the coverage of the big winter storm sweeping the country, you’d think that the coming cold temperatures were unprecedented. And, for sure, it’s a big storm. And temperatures are going to drop a lot. Might even set some records, somewhere.
But we tend to lose sight of the modern context. Winter nights are much warmer now, on average, than they were just a few decades ago. In the Washington DC area, what we perceive as an outrageously cold night in the 2020s was merely a cold night in 1980s.
In fact, the main temperature impact of global warming is exactly that — warmer nights. And while you can’t infer global warming by looking at temperatures at a single point on the planet, you can remind residents of the DC area that winter low temperatures used to be much lower, on average, than they are today.
Here’s the official temperature data from Dulles International Airport, via NOAA. I’ve simply taken the lowest recorded temperature for each calendar year, and plotted that. (The 9 degrees for 2022 (so far) occurred back in January 2022).
Source: Analysis of weather data via NOAA.
Every year in the 1960s, 1970s, and 1980s had a lower minimum temperature than we are expecting from this super-storm. Almost every year in the 1990s, 2000s, and 2010s, ditto.
Similarly, we can check how common a low of 8F or lower was, back in the day. And the answer is, relatively common. For Dulles Airport, in the 1960s to 1980s, an average year had between seven and eight nights when the temperatures dipped to 8F or colder.
Source: Analysis of weather data via NOAA.
What was once a commonplace wintertime occurrence in this area — nighttime low of 8 or lower — is now a rare event.
When I was a kid, if it only got down to 8F around here, and only did that for a single night? That would have been reckoned as an exceptionally mild winter. But now, that single 8F night is the remarked-upon cold weather event of the year. Such is the slow and subtle impact of global warming.
The sheer area of this storm is unusual. It will be packing some strong winds.
But around here, the “Siberian” temperatures it brings, with all the associated news hype, would not have been at all unusual half-a-century ago. They only stand out in the context of the much warmer average nighttime temperatures that we currently experience. The chill from this storm hardly registers as a blip in the overall trend of rising temperatures.
This is a brief followup to Post #1658., where I checked the UV protection provided by some eyeglasses, sunglasses, and car window glass.
Here, I’m validating that using an actual UV meter, marketed for safe tanning practices.
Recall the goal of this: I want to see how well my eyeglasses, sunglasses, and car windows block ultraviolet (UV) light. See my recent Post #1654 on this topic if you wonder why anyone would care about that. Continue reading Post #1658: Testing eyeglasses and sunglasses for UV protection. Part 2, the initial tests
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.
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.
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.
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.
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.
