How We Calculate EV Charging Costs

Every cost figure on this site uses the same formula and sources we name. Here it is, so you can check our math or swap in your own numbers.

The formula

Cost per mile is:

(kWh per 100 miles ÷ 100) × your electricity rate ÷ charging efficiency

Three inputs. Only one of them is ours to estimate.

Where each input comes from

Consumption (kWh per 100 miles). The EPA’s published rating for that model and year. We use the combined figure unless an article is specifically about highway or city driving.

Electricity rate. This is why national averages are so unhelpful. Rates vary by more than three to one across the US, and time-of-use plans can double within a single day. We start from your state’s average and let you replace it, because the number on your bill is the only one that counts.

Charging efficiency. You always pull more energy from the wall than ends up in the battery. We assume 90% for home charging. That’s an estimate, and we’d rather say so: real losses change with temperature and charging speed.

What we leave out

We keep these separate instead of hiding them inside a cost-per-mile figure:

• Charger installation — a one-off cost, not a running cost
• Battery wear — real, but too model-specific to average honestly
• Incentives and rebates — they expire and vary by location, so they get their own dated articles

When these numbers go out of date

Rates get revised and incentives run out. Every figure here shows the date we checked it. If that date is more than a year old, treat the number as a starting point and check your current rate. If you spot one that has drifted, tell us.