EV Solar Charging Calculator
Enter your array size, your sun hours, and how far you drive to see what share of your charging the roof covers, what it saves against grid power, and how long it takes to pay for itself.
A 7 kW array at 4.5 sun hours a day, charging a Tesla Model Y driven 35 miles a day
100% of your charging
The array makes about 25 kWh a day — enough to add roughly 79 miles of range, against the 35 you drive.
Solar wipes out the $650/yr grid charging bill, and the surplus earns another $821/yr in export credit. At $1,472/year saved, the $19,250 array pays for itself in 13.1 yr on charging savings alone.
Sizing check. Covering 100% of this car's charging takes about 3.1 kW of panels at 4.5 sun hours — roughly 8 modern 400 W panels, on top of whatever the house itself uses. A full 75 kWh pack from empty would take 3.4 daysof the array's entire output.
Solar array
A typical US home array is 6–10 kW. Peak sun hours run from about 3.5 a day in the Pacific Northwest to 6 in the desert Southwest; shade, a north-facing roof, or a shallow pitch cut it further. Run your own address through NREL's PVWatts for the real number.
Vehicle & driving
The US average is about 37 miles a day. Your daily mileage sets the energy the array has to make; the battery only sets how much of it the car can bank at once.
Electricity rate
The rate solar saves you from paying. A high rate is what makes solar charging pencil — the same array pays back roughly twice as fast in California as in Idaho.
What your utility pays for surplus
Exports credit at the full retail rate, so a kWh banked at noon covers a kWh pulled at midnight. Still the rule in most states — check your utility's tariff.
Install cost & incentives
$2.75/W × 7 kW = $19,250 before incentives. The federal 30% residential credit (Section 25D) was terminated for systems placed in service after December 31, 2025, so this defaults to 0% — check dsireusa.org for state and utility programs that still apply to you.
An annual energy balance, not an hourly simulation. It assumes solar you don't use immediately is banked with the utility (net metering) or credited at the export rate you picked, applies a 80% performance ratio for inverter and system losses (NREL PVWatts defaults), and grosses the car's energy up for onboard-charger losses. Without net metering or a home battery, only the kWh you charge while the sun is up actually come from your roof. Real production depends on your roof, shade, and weather — model your address at PVWatts before you buy.
How much solar do I need to charge an EV?
About 3.1 kW — roughly 8 of today's 400-watt panels — for an average driver. That is the whole answer, and it is smaller than most people guess: a third of a typical 7 kW home array, not a second roof.
The arithmetic behind it is two lines:
- What the car needs. 35 miles a day at the Tesla Model Y's 28 kWh/100 mi is 10 kWh into the battery — about 11 kWh off the meter once you allow for the 12% the onboard charger loses as heat. Call it 4,065 kWh a year.
- What a panel makes. One kW of panels at 4.5 peak sun hours yields about 3.6 kWh a day, after the ~20% lost to the inverter, wiring, soiling, and heat.
Divide one by the other and you get the array. Sun hours move it more than anything else: the same 35-mile day needs 2.3 kW in Phoenix and 4.0 kW in Seattle. Drive twice as far and you need twice the panels. And all of this sits on top of what the house itself burns — the car is an addition to the array, not the whole reason for it.
One caveat the arithmetic hides: this is an annual energy balance. Your panels make power at noon and your car usually charges at midnight. What reconciles the two is net metering — the utility banks your midday surplus and gives it back at night at the retail rate. Where net metering has been replaced by a low export rate, the timing stops being a formality and starts being the whole problem. See the section below.
Solar + EV vs grid charging cost
Grid charging the reference Tesla Model Y costs about $650 a year at the US-average 16.0¢/kWh — 5.1¢a mile, already about a third of what the same miles cost in a 30 mpg gas car. An EV-sized array wipes out essentially all of that bill, so the saving is the same $650 a year, and the $8,507 of panels repays itself in 13.1 years.
Which raises the point almost every solar-and-EV pitch gets backwards. The payback is driven by the price of the power you avoid, not by how much sun you get. Compare three real places, same car, same $3/W install:
| Where | Sun hours | Electricity | Array for the EV | Saved per year | Payback |
|---|---|---|---|---|---|
| California | 5.5 | 31.8¢ | 2.5 kW | $1,293 | 5.4 years |
| Arizona | 6.0 | 15.3¢ | 2.3 kW | $622 | 10.3 years |
| Washington | 3.5 | 11.4¢ | 4.0 kW | $463 | 23.6 years |
Arizona has the best sunlight in the country and a worse payback than California, because Californian power costs twice as much to avoid. Washington gets both the worst sun and the cheapest power — its 11.4¢/kWh hydro is so cheap that panels bought to charge a car take 23.6 years to break even, longer than the 25-year panel warranty. If your utility bill is small, solar has little to save you.
Two more things the table doesn't show. First, array size barely moves the payback under net metering — cost and output both scale with kW, so the ratio holds; you are buying the same deal in a bigger quantity. Second, spread the array's cost across its 25-year output and each solar kWh works out at roughly 8.9¢/kWh — cheaper than any utility in the country sells power for. Solar electricity really is the cheapest way to fuel a car. You just have to buy 25 years of it up front.
Best home solar setups for EV owners
What separates a good EV solar setup from a mediocre one is almost never the panels. It is whether the kWh your roof makes at noon can reach a car that plugs in at six.
- Find out what your utility pays for exports first. This single fact decides the design. Under full net metering, surplus banks at the retail rate and you can size freely, charge whenever, and skip the battery — the grid is your storage. Under a low export tariff (California's NEM 3.0 and the successor tariffs following it), exported kWh are worth a few cents and self-consumption is everything.
- Size for the house plus the car, not the car alone. The car adds only about 3.1kW of demand for an average driver; a typical home already needs 6–10 kW. Add them, and add the car's share before the install — panels are far cheaper per watt in the original job than in a second visit with its own truck roll, permit, and possible inverter swap.
- Move the charging into daylight if you can.The highest-return upgrade on this list costs nothing: schedule the car to charge midday when it's home, in the app or in the charger. On a low export rate that converts kWh worth a few cents into kWh worth full retail. (Under net metering with a flat rate, it makes no difference — check your tariff before you bother.)
- Consider a solar-aware Level 2 charger.Several units can track your array's live surplus and modulate the car's charge rate to match it — Zappi's Eco+ mode, Wallbox's Eco-Smart, SolarEdge's solar-boost charging. They need a current sensor on the meter and they only pay off if exports are poorly credited. On net metering they solve a problem you don't have.
- Treat the home battery as an export-rate decision.A powerwall-class battery is worth more than the panels themselves under a bad export rate and close to worthless under net metering. Price it against what it actually recovers — the gap between your retail rate and your export rate, times the kWh you'd otherwise export — and be skeptical of anyone selling it as an EV accessory.
- Don't buy panels to make a Level 1 setup work. Solar changes where the electrons come from, not how fast they arrive. If overnight charging can't keep up with your commute, that is a Level 2 charger question, and it costs a small fraction of an array.
Where this fits with the rest of the math
Solar is the last lever on a charging bill, not the first. The order that actually saves money is: charge at home instead of on DC fast chargers, then get on a time-of-use rate and charge overnight, then — if your retail rate is high enough to justify it — put panels on the roof. The EV charging cost calculator prices the first step, the home charger ROI calculator prices the hardware that makes it possible, and the EV vs gas TCO calculator folds the resulting energy cost into the lifetime comparison against a gas car.
An estimate, not a design. Production uses an annual energy balance — system kW × peak sun hours × 365 × a 80% performance ratio for inverter and system losses (NREL PVWatts defaults) — and assumes surplus is credited at the export rate you pick. Peak sun hours are annual averages from NREL solar-resource data (3.5–6 h/day across the US); model your own roof at PVWatts. Installed cost of $3/W is the 2026 national-average EnergySage quote before incentives; the range runs roughly $2.40–$3.35/W. Electricity rates are 2024 state averages from the EIA. The federal Section 25D residential solar credit was terminated for expenditures after December 31, 2025 (One Big Beautiful Bill Act, July 2025) — verify current federal, state, and utility incentives at irs.gov and dsireusa.org before you sign anything.
Frequently asked questions
How much solar do I need to charge an EV?+
Less than most people expect: about 3.1 kW of panels — roughly 8 modern 400-watt modules, or a third of a typical home array — covers an average Tesla Model Y driven 35 miles a day at 4.5 peak sun hours. The car pulls about 11 kWh a day from the meter, and each kW of panels makes roughly 3.6 kWh a day after inverter and system losses. Sunnier sites need less (2.3 kW in the desert Southwest); the Pacific Northwest needs about 4.0 kW for the same miles.
Can solar panels fully charge an electric car?+
On an annual energy basis, yes — an array of a few kW makes more kWh over a year than an average commute consumes. But "fully charge" hides a timing problem: the sun shines midday and most people charge at night. Unless you have net metering (which banks your surplus with the utility at retail), a home battery, or the ability to plug in during daylight, the solar kWh and the charging kWh never meet. Net metering is what makes the annual balance in this calculator behave like real money. Without it, only the kWh you charge while the sun is up genuinely come from your roof.
How much does solar charging save vs charging from the grid?+
For the reference Tesla Model Y, grid charging at the US-average 16.0¢/kWh costs about $650 a year — 5.1¢ a mile. A solar array sized to that car erases essentially all of it, so the saving is the same $650 a year. That is real, but it is not a huge number, which is the honest headline: EV charging is already cheap, so solar's job is to shave an inexpensive bill, not an expensive one. The savings scale directly with your electricity rate — in California at 31.8¢/kWh the same car saves about $1,293 a year.
What is the payback period on solar for EV charging?+
At the national average — $3/W installed, 4.5 sun hours, 16.0¢/kWh power — an EV-sized array repays itself in about 13.1 years on charging savings alone. What moves that number is not the amount of sun but the price of the power you avoid: California (5.4 years) beats sunny, cheap-power Arizona (10.3 years), and the Pacific Northwest's 11.4¢/kWh hydro power stretches it to 23.6 years. Note the array outlives the payback in every case except the last — panels are warrantied 25 years.
Does the payback change if I build a bigger array?+
Under full net metering, barely — and that is the most useful thing on this page. Payback is (cost per watt) ÷ (annual kWh per watt × your rate), and none of those terms depend on array size. A 7 kW whole-home array at the reference site produces 9,198 kWh a year, of which the car uses only 4,065 kWh; the surplus offsets household load or exports at retail, and the whole thing still pays back in about 13.1 years. Where size does matter is under a low export rate (California's NEM 3.0 and similar successor tariffs): then every surplus kWh is credited at a few cents instead of retail, and oversizing gets punished.
Is a home battery worth it for solar EV charging?+
It depends entirely on your export rate, not on the EV. With full net metering the grid is already a free battery that credits you at retail — buying a physical one to charge the car adds cost with little return. Under a low export tariff, the picture flips: surplus you'd otherwise export at a few cents becomes surplus you store and use at retail, and the battery starts to make sense. The cheaper move most owners should try first is free: schedule charging for daylight hours whenever the car is home, which turns exported kWh into self-consumed kWh at no cost at all.
Is there still a federal tax credit for home solar in 2026?+
Not for a system you buy yourself. The Section 25D Residential Clean Energy Credit — the 30% credit homeowners had claimed for years — was terminated by the One Big Beautiful Bill Act (signed July 2025) for expenditures made after December 31, 2025. A system placed in service in 2026 gets no federal residential credit, which is why this calculator defaults the incentive to 0%. State rebates, utility programs, and some third-party-owned lease/PPA structures still carry value; check the DSIRE database (dsireusa.org) for your ZIP before assuming any discount. The separate 30C credit for the EV charger itself is a different rule — the home charger ROI calculator covers it.
How much cheaper is a solar mile than a gas mile?+
Once the array is paid for, the marginal fuel cost of a solar mile is zero, and even counting the panels it is very low: spreading the reference array's cost over its 25-year output puts a solar kWh at roughly 8.9¢/kWh — well under the 16.0¢ you pay the utility. At the Tesla Model Y's 28 kWh/100 mi, that is a fraction of a cent-per-mile world that no gas car can reach. The catch is the capital: you pay 25 years of fuel up front.
Keep going
- EV Charging Cost Calculator — what your charging costs today at home, public L2, and DC fast, before any panels.
- Home Charger ROI Calculator — the Level 2 install that has to happen before solar charging is worth anything, and how fast it pays back.
- EV vs Gas TCO Calculator — the lifetime comparison, with your energy cost folded in alongside depreciation, insurance, and maintenance.
- EV Charging Cost by State — the retail rate you'd be avoiding, state by state. It decides whether solar pencils.