Electric vs. Gasoline efficiency with a Plug In Hybrid Vehicle
2025-12-30 14:31 - General
Almost exactly three years ago I was moving and needed a vehicle. I was interested in getting an EV but not excited about paying new vehicle prices, and unsure if I could expect (post move) reliable access to charging, so an EV as my only vehicle might be a risky prospect. I eventually decided on a used plug-in hybrid, with a bit of EV only range but also a regular gasoline engine for longer trips. Overall, this has worked out great for me so far.
Not too long after getting it, with the ability to go both full EV and traditional gasoline powered, I started to wonder: what's the cost efficiency of driving on battery power vs. gasoline power? I've got some notes based on documented average data (not my car) that gives a ratio of 1.89: gasoline being almost twice as expensive as electricity per mile. I also know I carefully measured my own vehicle, but I think I did a 100% to 0% EV only trip and recorded the distance and electricity in, and I also did a significant fraction of a full gas tank, in that 0% (i.e. hybrid-only) battery state. I wrote the numbers down on paper and remember a very similar two-to-one ratio (but don't have that piece of paper anymore). So I've been charging at every opportunity, and driving EV only whenever practical ever since.
A comment online was claiming very different numbers, but in a vague hand-wavy sense. I thought it must be wrong, can't be so different from what I've measured, so I tried to prepare some actual documented numbers from my own vehicle and experience... and found that indeed, the numbers are very different today!
I might not have taken things like charge/conversion efficiency into account, or I don't know what else. But I've decided to throw together a quick tool to help me figure this out once and for all. Put in: your (marginal) electrical cost per kWh, your cost of gasoline, plus your capacity and distance values. If you've typed in one cost (per unit) and not the other, that other will be calculated as the equivalent cut-off rate. So e.g. because electrical costs are more stable than gasoline: fill in all numbers besides your cost for gasoline and it will tell you the cutoff cost. When gasoline costs less than this, it's cheaper to drive on gasoline than electricity!
If possible, you should give the full amount of electricity consumed. (I have a charger (EVSE) that will report the total energy delivered in a charging session.) There are delivery, conversion, and charging losses and you pay for all the energy lost at each step. Unit labels are for my convenience. If you'd rather type in liters or kilometers or anything else, just ignore the unit labels.
At the time I write this: local gasoline was $2.499/gal while electricity was 22.966¢/kWh. Two years ago electricity was 17.219¢/kWh (so it's gone up by 33%) while gasoline was $3.019 (so it's gone down by 21%). With the most reliable distance/capacity numbers I can look up easily (it takes a time and just the right trips to gather really accurate ones): the energy cost of electricity today is about 38% more than gasoline, to drive the same distance. Quite a difference from the 50% less I calculated a while ago, probably with some bad assumptions or rounding making that number even further off.
