An EV can materially increase annual electricity use. The amount of extra solar that may be useful depends on how far the vehicle travels, its efficiency, when it is normally charged and whether charging can happen while solar is producing.
Charging time changes the answer
Daytime charging can use solar directly. Evening or overnight charging may rely more on the grid, or may make storage worth investigating if there is enough daytime surplus to charge the battery first.
Do not size only from old bills
If the EV is new or still planned, historical bills will not show the future charging load. I add a reasonable estimate of future EV consumption before comparing system sizes.
Home and business charging can be different
A home EV may spend the day away from the property and charge at night. A commercial fleet may return at different times, or vehicles may be onsite during daylight hours. The charging pattern matters as much as the annual kilometres.
EVs can change the battery decision too
An EV can increase later electricity use, but that does not automatically mean a stationary battery should be larger. I still check how much solar surplus is available, what the grid tariff is, and whether direct daytime charging provides a better result.
Example
A homeowner with a small existing solar system buys an EV and plans to charge mainly overnight. Before adding a large battery, I would compare more solar, charging-time changes and battery options rather than assuming storage is the only solution.
What I ask
- Which EV is owned or planned?
- Approximate kilometres driven each week
- When the vehicle is usually at the property
- When charging is likely to happen
- Existing charger or planned charger
- Whether more EVs may be added
- Existing solar and battery setup
The system should be designed around where the customer's energy use is heading, not only where it has been.