EV Charging Cost at Home vs Charging Station

Formula

session cost = energy added / efficiency x price per kWh + fixed fees

monthly mix cost = monthly wall energy split by home and public charging share

Example

A 40 kWh charge at 0.16 per kWh at home can cost much less than the same energy at a 0.48 per kWh public charger, especially when fixed public session fees are added.

Inputs to compare before choosing home or public charging

A fair comparison uses the same wall energy and includes the charges that actually apply to each option.

Do not treat example rates as official prices. Check the current utility plan and charging-network terms before budgeting.

Assumptions and limits

• Example rates are not official current prices.
• Public charging may include extra time-based, idle, congestion, or membership fees.
• Compare equivalent all-in rates when budgeting, or treat the result as a rough comparison.

How to read the result

The result compares the same wall energy at your home rate and public rate. A positive difference means the public session costs more; a negative difference means the public option is cheaper for the inputs entered.

• Home cost uses wall energy and the home per-kWh rate.
• Public cost uses wall energy, public per-kWh rate, and the public session fee.
• Difference over 10, 50, and 100 charges shows how a small per-session gap grows over repeated charging.
• Monthly and annual differences multiply the same session gap by the charge count you enter.
• Mixed monthly cost uses monthly miles, vehicle efficiency, home charging share, public price, and public session fees.
• All-home and all-public monthly costs show the outer bounds for the same monthly driving estimate.
• The comparison is only fair when both rates include the same kinds of fees and taxes.

Worked examples

These examples show why public charging can be useful for a trip but expensive as a daily substitute for a home overnight session.

• Home Level 2: 40 kWh added at 90% efficiency and 0.16 per kWh costs about 7.11.
• Public AC charging: the same wall energy at 0.30 per kWh plus a 1.00 fee costs about 14.33.
• DC fast charging: the same wall energy at 0.48 per kWh plus a 2.00 fee costs about 23.33.
• Cold-weather or low-efficiency session: lower efficiency increases both home and public costs because more wall energy is purchased.
• Monthly savings example: if public charging costs 16.22 more per session and you charge four times per month, the public premium is about 64.89 per month and 778.67 per year.
• Monthly mix example: 1,000 miles at 3.5 miles/kWh and 90% charging efficiency uses about 317 wall kWh. If 70% is charged at home and 30% publicly, the mixed cost sits between the all-home and all-public estimates.

Common input mistakes

The comparison can be misleading when one side includes all fees and the other side includes only energy charges.

• Entering battery energy instead of wall energy without efficiency adjustment.
• Leaving out public session fees, idle fees, parking fees, or taxes.
• Using a home supply-only rate while comparing it with an all-in public price.
• Assuming one public charging network price applies to every station.
• Comparing a slow destination charger with a highway DC fast charger as if speed had no value.
• Treating the home charging share as exact when real monthly behavior changes by trip, season, and charger availability.

What to check next

Before treating the difference as a budget number, check both original price sources and decide whether you are comparing energy-only or all-in costs.

• Utility bill for supply, delivery, taxes, riders, and time-of-use period.
• Charging app or receipt for station price, fees, discounts, and taxes.
• Trip context: public charging may cost more but save time or make travel possible.
• Recent charging history if you want to compare monthly or yearly behavior.
• Monthly charge count when turning a per-session difference into a household budget estimate.
• Monthly miles and recent efficiency when estimating a home/public mix for normal driving.

FAQ