Solar + EV Planner

An average US driver covers about 12,000 miles per year. At 3.5 mi/kWh and 10% charging losses, that's roughly 3,800 kWh per year at the wall. In a sunny state with 5.5 peak sun hours, you need about 2.4 kW DC of solar, roughly six 400 W panels.

Heavier drivers, less efficient EVs (trucks, large SUVs), or cloudier states all push the panel count higher. Use the calculator above with your actual numbers; the math scales linearly with miles and inversely with efficiency.

Once your solar panels are paid off, charging from solar is essentially free: just a small share of inverter and panel maintenance spread across the kWh. Grid charging costs your utility rate per kWh divided by your EV's efficiency.

At 14¢/kWh and 3.5 mi/kWh that's about 4¢/mile from the grid versus less than 1¢/mile from owned solar. Both beat gasoline by a wide margin; at $4.00/gallon, a 28 MPG gas car costs about 14.3¢/mile.

With net metering at or near the retail rate, you can skip the battery. Your daytime solar exports get credited against your overnight charging draws; the grid effectively acts as your battery for free.

If your utility uses export rates well below retail (California NEM 3.0 credits exports at roughly 25% of retail), a home battery starts to pay back faster, especially paired with time-of-use rates. Our battery sizing tool walks through a full sizing pass.

Not for purchases made now. The 30% residential solar credit (Section 25D) was terminated for installations completed after December 31, 2025, and the $7,500 federal EV credit (Section 30D) ended for vehicles acquired after September 30, 2025, both under the One Big Beautiful Bill Act.

Leased solar systems and leased EVs can still carry commercial credits claimed by the leasing company, which sometimes shows up as a lower monthly payment. State incentives for both solar and EVs vary widely; check the DSIRE database for your area.

Size for the car's annual usage. A 7.2 kW Level 2 charger can pull power faster than your solar produces in the moment, but it only runs a few hours a day. The annual kWh is what determines panel count.

Net metering smooths the moment-to-moment mismatch between when the sun shines and when you plug in. If you're fully off-grid, sizing changes; see our off-grid calculator.

Cold weather hits both sides: EV efficiency drops 20–40% in winter (battery heating, cabin heat, denser air resistance), and solar production drops with shorter days and lower sun angles. We use annual averages, so winter dips and summer peaks roughly cancel for a fixed rooftop system.

If you live somewhere with brutal winters and you charge mostly overnight, bump the miles-driven figure up 10% or efficiency down 10% to stress-test the math. Snow-covered panels also lose a few weeks of production each year, typically less than 5% annually.