Path-Q Solar

How should a planned electric vehicle change the size of my solar system?

Answer

Include the EV's expected annual charging electricity in the future-use baseline, then size solar against the combined household and vehicle demand if the plan is sufficiently certain. The estimate should reflect driving distance, vehicle efficiency, charging losses, and whether charging occurs at home.

Key points

  • An EV can materially increase annual electricity use, but the amount varies with miles driven and vehicle efficiency.
  • Home charging, public charging, seasonal driving, and charging habits affect the home load.
  • If the purchase or mileage is uncertain, model a range rather than adding the maximum load automatically.
  • The electrical service, panel capacity, charger location, and charging schedule also need review.

What it depends on

  • Expected annual mileage
  • Vehicle efficiency and charging losses
  • Share of charging done at home
  • Charging schedule and future utility treatment
  • Existing solar capacity and roof limitations

Risks and trade-offs

  • Sizing for an EV that is never purchased can create excess capacity.
  • Ignoring a likely EV can leave the system undersized or require later expansion.
  • A larger system may require electrical upgrades or a different interconnection design.

Information you may need

  • Vehicle type or efficiency estimate
  • Annual mileage and home-charging share
  • Charging equipment plans
  • Current electricity use and available roof area

Your next step

What to do next

Ask for two designs—current load and current load plus a documented EV scenario—and have the installer identify any service or charger constraints.

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