Charging an EV at Home vs Public: The Real Cost Gap

The headline EV pitch — “pennies per mile” — is true at home and often false at a public fast charger. The same car can cost $0.04/mile plugged into your garage overnight and $0.15/mile at a highway DC fast charger. That 3–4× gap is the single biggest variable in an EV’s running cost, and it’s entirely about where you plug in.

Where the gap comes from

Cost per mile to charge is just:

$/mile = (price per kWh ÷ charging efficiency) × (kWh per mile)

Two of those three terms change dramatically between home and public:

Price per kWh. Residential electricity in the US averages roughly $0.16/kWh. Public DC fast charging commonly runs $0.40–$0.60/kWh — a premium for the convenience and the hardware.
Charging efficiency. Some energy is lost as heat. Home Level 2 charging is ~85–90% efficient; fast charging is similar but the price is what dominates.
kWh per mile. A property of the car (~0.25–0.35 kWh/mi for most EVs), the same wherever you charge.

So the per-mile gap is mostly the price-per-kWh gap, multiplied across every mile you drive.

A worked comparison

Say your EV uses 0.30 kWh/mile at 88% efficiency:

Home at $0.16/kWh: 0.16 ÷ 0.88 × 0.30 ≈ $0.055/mile
Public at $0.50/kWh: 0.50 ÷ 0.88 × 0.30 ≈ $0.17/mile

Over 12,000 miles a year that’s ~$660 at home vs ~$2,040 on the road — a $1,380 swing purely from where you plug in. Most owners land in between, charging mostly at home with occasional road-trip fast charging.

Find your own number

Enter your rate, the car’s efficiency, and your annual miles to see per-charge, per-mile, and per-year cost:

Your numbersSaved on this device only

Battery size

kWh

Usable pack capacity.Efficiency

mi/kWh

Real-world miles per kWh.

Home rate

$/kWh

Electricity price at home.Public rate

$/kWh

Average public charging price.

Public share

% of charging done in public.Charging loss

Energy lost charging (~10%).

Annual miles

Roughly how far you drive per year.

Compare to gas MPG

mpg

Optional. 0 to skip.Gas price

Per gallon, for the comparison.

🔋 Annual charging cost

$830

$0.069/mi · $69/mo

Blended rate: $0.218/kWhhome / public weighted
Range / charge: 263 mi
Full home charge: $13
Annual energy: 3,810 kWh

Run it twice — once at your home rate, once at a typical public rate — and weight by how often you actually use each. That blended number is your true cost per mile.

What shifts the gap

Time-of-use plans. Charging overnight on an EV rate can drop home cost below $0.10/kWh, widening the gap further.
Free workplace or destination charging. Drops part of your miles to ~$0.
No home charging at all. If you rely on public charging, an EV’s running-cost advantage over gas shrinks — sometimes to nothing. Worth modeling before buying.
Cold weather. Raises kWh/mile (more energy per mile), hitting both home and public cost.

What this doesn’t model

Charger installation — a Level 2 home charger is a one-time cost, not per-mile.
Battery degradation over years.
Idle/session fees some networks charge on top of per-kWh.
Demand charges baked into some commercial fast-charging pricing.

The one-line version

Home charging is cheap because residential electricity is cheap; public fast charging costs 3–4× more per kWh, and that premium hits every mile. If you can’t charge at home, run the public-rate number before assuming an EV saves you money.

EV Charging Cost Calculator — per-charge, per-mile, per-year on your rates.
What It Really Costs to Charge an EV — the full charging-cost breakdown.
Gas vs Electric Total Cost — the whole-ownership comparison, not just energy.
Fuel Cost Calculator — the gas-side number to compare against.

AutoMath is an educational tool, not financial advice. Costs depend entirely on your rates and driving.