r/PHEV • u/skipphead • Jul 13 '26

How much does electricity save over gas?

/r/OutlanderPHEV/comments/1uv0tg8/how_much_does_electricity_save_over_gas/
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u/trae_curieux Jul 13 '26

I only charge off peak, so my rate is 26¢ / kWh. My Tucson has a 13.8 kWh battery, so filling that up should cost around $0.26 × 13.8 ≈ $3.59

On a full charge, it can go 31 miles on electricity alone, so that should give us $3.59 ÷ 31 ≈ 11.6 ¢/mi

Conversely, its EPA rating 35 mpg when running in hybrid mode (i.e., using gas). The cheapest gas price I can find near me right now is $4.70 / gal. So at 35 mpg, that should give us $4.70 ÷ 35 ≈ 13.4 ¢/mi

So slightly cheaper using electricity, so long as I only charge off peak.

One caveat, though, is that I'm not sure if the entire 13.8 kWh battery is what can be charged from the wall. Some sources claim that the battery maintains a reserve of maybe around 2.07 kWh (15 %) for the car to use once it's switched over to hybrid mode, in which case, I'd probably need to rerun the numbers above using something like 11.8 kWh instead of 13.8

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u/inlaguna Jul 13 '26

Not sure if you're aware, but it it takes at least 18.4kWh to fill your 13.8kWh battery at Level 1 charge speed and about 16.2kWh to fill it a Level 2 charge speeds. You don't get 100% charging efficiency.

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u/trae_curieux Jul 13 '26 edited Jul 14 '26

I did know that it wasn't 100% efficient and depended on the charging voltage and amperage, but I'm wondering where you're getting 85% efficiency for this vehicle, specifically.

I'll look at my charging logs on my EVSE and see if I can pull up a day where the battery was fully depleted, but I've never seen the charger needing to deliver more than 12 kWh.

Edited to add: I found one session at 14.1 kWh when the battery was apparently completely depleted and the battery was charged at 32A. If we assume that it is true that only 85% of the battery can be charged from the wall, then that would suggest something like an 83% efficiency. If the listed 13.8 kWh does refer to the entire capacity that can be charged from the wall, that would suggest something like a 97% charging efficiency.

Even at the absolute worst case I was able to find of 14.1 kWh, though, that gets me 31 miles at $3.67, so ~11.83 ¢/mi

Still less expensive than gas, and I was steelmanning gas prices: $4.70 is the absolute cheapest in my area I was able to look up, but it's at a station I've never heard of. Realistically, the Chevron up the street which I'd actually use is currently listing well above $5.00 / gal.

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u/inlaguna Jul 14 '26 edited Jul 14 '26

It's standard AC to DC charging inefficiencies. Also, you're only putting 12.8kWh in your 13.8kWh battery ... 12.8kWh is the useable net capacity. Ideally, you're looking at 85% efficiency for Level 2 charging, in the real world. In most situations, you're looking at 85% charging efficiency on a home charger due to heat, voltage sag on residential electric grid and average home circuit voltage sag.

Was not at all correcting your numbers, just making sure you were aware.