Path-Q Solar
How much solar capacity should I reserve for charging an electric vehicle?
Answer
Estimate the EV's annual electricity use first, then add that energy to the home's expected annual load rather than reserving a fixed panel count. The required solar capacity depends on driving distance, vehicle efficiency, charging losses, local production, charging schedule, and how exported energy is valued.
Key points
- Estimate annual EV energy by dividing annual miles by efficiency expressed in miles per kWh, or by multiplying annual miles by consumption expressed in kWh per mile, then add an allowance for charging losses.
- The same annual energy can require different solar capacity depending on the site's production per unit of capacity.
- Charging during solar-producing hours can increase direct use; nighttime charging may rely more on grid energy or stored solar.
- Include future changes such as a second EV, increased driving, or workplace charging.
What it depends on
- Annual driving distance
- Vehicle efficiency and charging losses
- Solar production at the site
- Charging schedule and billing treatment
Risks and trade-offs
- A mileage estimate can be wrong if driving patterns change.
- Sizing for all EV energy may produce excess generation if much charging occurs elsewhere.
- Panel capacity alone does not guarantee charging availability during cloudy periods or outages.
Information you may need
- Expected annual miles and vehicle efficiency
- Home charging level and schedule
- Current and future household electricity use
- Site-specific production estimate
Your next step
What to do next
Add the EV's estimated annual charging energy to the household load and request production scenarios for daytime, nighttime, and flexible charging.
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