Solar and EV Charging: Does an Electric Car Change the Math?

An electric car adds a large, steady load to your home, roughly 3,000 to 4,000 kWh a year for 12,000 miles of driving, which is about 2.3 to 3.1 kW of extra solar panels in much of the U.S. Whether those extra panels pay off depends mostly on your export rules and when you charge. Under full retail net metering, it hardly matters when the car plugs in. Under net billing, solar saves full price only when the car charges while the sun is up, and a cheap overnight EV rate may beat adding panels. Here is how to think it through.

How much electricity does an EV use?

Most EVs travel about 3 to 4 miles per kWh, depending on the vehicle, speed, temperature and driving style. Charging losses add a bit more.

Miles per year	At 3 miles/kWh	At 3.5 miles/kWh	At 4 miles/kWh
8,000	About 2,700 kWh	About 2,300 kWh	About 2,000 kWh
12,000	About 4,000 kWh	About 3,400 kWh	About 3,000 kWh
15,000	About 5,000 kWh	About 4,300 kWh	About 3,750 kWh

For context, adding 3,400 kWh a year to a home that uses 10,000 kWh is a 34% increase.

Your car’s app or your charger may show actual kWh per mile. If you already have an EV, check your utility account for the change in usage since you got it.

What charging costs without solar

At the July 2026 U.S. average residential rate of 18.31 cents per kWh (EIA), 3,400 kWh costs about $620 a year. On a discounted overnight EV rate, it can be much less.

For comparison, if a gas car gets 30 mpg and gas costs $3.50 a gallon (use your local price), 12,000 miles costs about $1,400 a year in fuel. The EV usually saves money on fuel by itself, with or without solar.

So the question is not “EV or solar.” It is whether adding panels to cover the EV beats buying that power from the grid.

How the extra panels pay off

Adding about 2.6 kW at $3.00 per watt costs about $7,800. At 1,300 kWh per kW, those panels make about 3,380 kWh a year. What they save depends on your export rules and charging schedule.

Situation	Value of the extra 3,380 kWh	Simple payback on $7,800
Retail net metering, 18¢ rate	About $608 a year	About 12.8 years
Retail net metering, 28¢ rate	About $946 a year	About 8.2 years
Net billing, car charges at midday (worth 18¢)	About $608 a year	About 12.8 years
Net billing, car charges overnight, exports earn 5¢	About $169 a year	About 46 years

These are simple paybacks before rate increases, panel degradation and inverter costs. See solar payback period for the full method.

Under full retail net metering

Your utility credits exported power at about the same rate you pay. Panels can export at noon and the credit covers overnight charging. Adding panels for an EV is worth about the same per kWh as the rest of your system. If solar pays for your home, extra panels for the EV usually do too.

States with full or near-retail net metering, as of October 2026, include New York, Massachusetts, New Jersey and Colorado, among others. Check your state page.

Under net billing or reduced export credits

This is where EVs get tricky. In California’s Net Billing Tariff, exports average roughly 4 to 5 cents per kWh. Other states and utilities have moved to similar systems. See net metering explained and California net billing (NEM 3.0).

If your car is away at work all day and charges at night, the extra panels mostly export at a low credit, while the car charges from the grid at your normal or off-peak rate. The panels barely help the EV.

What changes the answer:

• Charging during the day. If you work from home, are retired, or have a second car that sits at home, schedule charging for late morning to mid-afternoon. Then the car soaks up solar that would otherwise export cheaply.
• Solar-following chargers. Some smart chargers and apps adjust charging speed to match surplus solar.
• Workplace or public charging may change how much you need to charge at home at all.

Time-of-use rates and EV plans

Many utilities offer time-of-use plans or special EV rates with cheap overnight power and expensive late-afternoon and evening power.

• For EV charging, cheap overnight power is often the lowest-cost option without solar.
• For solar, TOU rates affect how much your exports and self-use are worth. Under some TOU net billing plans, exports in summer evening hours earn more.
• The key is to avoid charging during the peak window, typically late afternoon and evening, when rates are highest and solar is fading.

If your utility has an EV rate, compare it to the value of extra panels. When off-peak power is cheap and exports earn little, the cheap overnight rate can be the better deal. See time-of-use rates and solar.

Should you size for a future EV?

Adding panels later usually costs more per watt than including them at the start, because of a new permit, design and crew visit. But paying today for an EV you may not buy for years ties up money for nothing.

It usually makes sense to size for an EV if:

• You expect to get one within about two or three years.
• Your utility credits exports at or near retail, or you can charge during the day.
• Your roof has room.
• Your utility allows a system larger than your past usage. Some cap system size based on 12 months of history, so ask the installer to confirm.

It usually does not make sense if:

• The EV purchase is uncertain or far off.
• You are under net billing and will charge mostly overnight.
• Your roof space is limited and better used for current loads.

A middle path: make sure the inverter and electrical panel have room to add panels later, then decide when the EV arrives. See how many solar panels do I need.

Electrical upgrades to plan for

• Level 2 charger. Most EV owners want a 240-volt charger at home. Costs vary from a few hundred dollars to much more depending on wiring distance and panel capacity.
• Main panel capacity. Adding solar, an EV charger and maybe a heat pump at once can require a main panel or service upgrade. Ask your installer and electrician to plan them together, so you only upgrade once. Make sure any needed upgrade is in the solar quote, not a surprise later. See hidden electrical upgrades.

Batteries and EVs

A typical home battery stores about 13.5 kWh and costs roughly $12,000 to $16,500 installed in 2026. Many EV batteries are several times larger. Using a home battery to charge a car is usually a poor use of it: it drains your backup reserve, adds wear and does not move much energy.

Some newer EVs and chargers support vehicle-to-home backup, where the car powers the house during an outage. This depends on the specific vehicle, charger and utility rules, and adds cost. If it matters to you, ask about compatibility before buying a home battery. See do solar batteries pay off and generator vs battery backup.

Watch out for these sales claims

• “Your car will run on free sunshine.” The panels cost money, and under net billing the timing matters.
• “Add a battery to charge your EV at night.” Rarely the cheapest option.
• Oversized systems sold for a “future EV” you have not committed to. See oversized system.

Bottom line: An EV makes solar more attractive under retail net metering or if you can charge during the day. Under net billing with overnight charging, a cheap EV rate from your utility may beat adding panels.

Model your home with and without the EV load in the calculator, and compare system sizes in compare options.