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.
