EV charger tools

Charging time. The number that matters is the delivered power, which is the lower of the wall unit's output and your car's onboard AC limit. AFDC puts residential Level 2 at up to 30 amps delivering 7.2 kW, with the class spanning 7.2 to 19.2 kW; Level 1 is about 1.9 kW. Divide the energy you need by that figure and add some overhead for charging losses.

Cost per mile. AFDC's method: cost of electricity in dollars per kWh, times the vehicle's kWh per 100 miles, divided by 100. Their worked example — 10.7 cents per kWh, 27 kWh per 100 miles — gives about $0.03 per mile, and about $6 for a full charge on a 200-mile EV with a 54 kWh battery. Swap in your own rate; that's the whole trick.

Quote comparison. Five lines: hardware ($600–$1,200 for Level 2), labor ($1,200–$2,000), wiring ($6–$12 per linear foot), permits ($100–$200), panel work ($0 or $1,500–$4,000). Any quote that can't be mapped onto those lines is hiding something.

DOE also publishes its own tools — a Vehicle Cost Calculator for comparing fueling costs between models, and a station locator. Those are free, neutral and worth using before you accept a vendor's calculator that happens to recommend their product.

How to choose

Use the lower of car limit and charger output

Every charging-time calculator that ignores the vehicle's onboard AC limit gives you a fantasy number.

Put your real utility rate in

AFDC's 3 cents per mile assumes 10.7 cents per kWh. Your rate may be double that, or half on an off-peak plan.

Add losses to any time estimate

Charging isn't 100 percent efficient. ENERGY STAR notes Level 2 is on average about 10 percent more efficient than Level 1 — neither is lossless.

Prefer DOE's calculators to vendor ones

AFDC's Vehicle Cost Calculator has no product to sell you.

Model an off-peak scenario before you buy

If your utility offers a time-of-use rate, run the cost per mile both ways. It sometimes matters more than the charger choice.