Battery sizing when you charge an EV at home

Home EV charging can add several kilowatt-hours per day — sometimes more than air conditioning in winter. If you charge at home most nights, storage sizing should at least acknowledge that load, even when much of it falls outside solar hours.

How the calculator models EV use

On the appliance step you enter kilometres driven per week. We convert that to a daily average using a typical consumption figure (about 17.5 kWh per 100 km for a mixed fleet of modern EVs). That daily kWh is added to your load breakdown when load details are enabled.

Example: 350 km/week ≈ 50 km/day → roughly 8.8 kWh/day of charging energy. That is not a full charge every night for every car, but it is a honest order-of-magnitude for planning.

When EV load should change battery size

If your bill averages already include EV charging (because you charge from the grid and it shows up on the bill), turning on the EV load in the calculator may double-count. Use the appliance view when bills pre-date the EV, or when you want a second estimate to compare against bill-based totals.

If you charge overnight on off-peak tariffs, the calculator does not model tariffs — it only counts energy. Financial optimisation is separate from kWh capacity.

Solar, EV, and battery together

Daytime solar may cover some driving if you charge while the sun is up. Night charging relies on stored solar or grid imports. A battery sized only for pre-EV bills can feel small once commuting kilometres rise. Re-run the calculator when your weekly km changes materially.

See also how battery size is estimated for cover hours and reserve.