How Many Solar Panels to Charge an Electric Car? EV Solar Calculator

Work out how many extra solar panels it takes to cover your electric car's charging, how many kWh it uses a year, and what that power and the gas it replaces cost. Use it when sizing a new system or adding panels for an EV.

Your state

Fills in typical rates and sunshine for your state. You can change any value.

Miles driven per year

Check your odometer or last service record.

EV efficiency

Listed on the EPA label and fueleconomy.gov; most EVs use 25–40.

Yearly output per kW

kWh a 1 kW system makes in a year where you live (NREL PVWatts is the best free source).

Panel wattage

Most home panels sold in 2026 are about 400–450 W.

Electricity rate

Your all-in price per kWh: total energy charges divided by kWh used.

More optionsFewer options

Charging losses

Energy lost between the wall and the battery.

MPG of the car it replaces

Use 0 to skip the gas comparison.

Gas price

Local average per gallon.

Your result

Extra panels for the EV 8 panels

Extra solar capacity: 2.96 kW
EV charging per year: 4,000 kWh
Cost to charge from the grid: $728
Gas cost it replaces: $1,371

Charging this EV takes about 4,000 kWh a year. Covering that with solar needs roughly 8 panels (2.96 kW) on top of what your home already needs.

Educational estimate only. Not financial, tax or legal advice.

Yearly fuel cost: gas vs grid vs solar

Cost per year

View as table

Fuel	Cost per year
Gasoline	$1,371
Grid power	$728
Own solar	$0

Compare yearly mileage

Result	A 8,000 miles	B Your inputs	C 18,000 miles	Difference (B − A)
Charging per year	2,667 kWh	4,000 kWh	6,000 kWh	+1,333 kWh
Extra panels	5	8	12	+3
Gas cost replaced	$914	$1,371	$2,057	+$457

Results update as you type. Without JavaScript you see the worked example below.

How to use it

Pick your state to fill a typical electricity rate and yearly output per kW.
Enter the miles you drive per year and your EV's efficiency in kWh per 100 miles from its EPA label.
Enter the panel wattage you plan to install.
Under advanced, set charging losses and the MPG and gas price of the car the EV replaces.
Read the extra panels, solar capacity and yearly charging kWh, then compare the mileage scenarios.

On this page

How many solar panels to charge an electric car? Turn your yearly miles into kWh, add charging losses, then divide by what 1 kW of panels makes where you live. With the defaults, 12,000 miles at 30 kWh per 100 miles needs about 4,000 kWh a year, or 8 extra 400 W panels (2.96 kW of capacity).

How to use the EV solar calculator

Your state. Fills a typical Electricity rate and Yearly output per kW.
Miles driven per year. From your odometer or service records. Default 12,000.
EV efficiency. kWh per 100 miles from the EPA label or fueleconomy.gov (opens in a new tab). Default 30.
Yearly output per kW. kWh that 1 kW of panels makes in a year at your home. Default 1,350; PVWatts (opens in a new tab) gives your local figure.
Panel wattage. Default 400 W.
Electricity rate. Used for the grid charging cost. Default 18.2¢ per kWh.
Advanced fields. Charging losses (10%), MPG of the car it replaces (28; enter 0 to skip the gas comparison) and Gas price ($3.20 a gallon).

The results show extra panels, extra solar capacity, charging kWh per year, the cost to charge from the grid and the gas cost it replaces. A bar chart compares yearly fuel cost for gasoline, grid power and your own solar (shown as $0 fuel cost, since the panels' price is not included). A scenario table reruns your inputs at 8,000 miles, your mileage and 18,000 miles.

How the calculation works

Charging kWh   = miles × (kWh per 100 mi ÷ 100) ÷ (1 − charging losses)
Extra kW       = charging kWh ÷ yearly output per kW
Extra panels   = round up (extra kW × 1,000 ÷ panel watts)
Grid cost      = charging kWh × electricity rate
Gas cost       = miles ÷ MPG × gas price

Assumptions that match the code:

Extra capacity is the exact kW needed, while the panel count is rounded up, so the panels' actual kW is slightly higher.
Yearly balance. Solar output and charging are matched over a year, not hour by hour, which assumes export credits carry value across time.
One flat electricity rate, with no time-of-use or EV rate plan.
No panel or charger cost; this tool sizes the solar and compares fuel costs only.

Worked example

Default inputs: 12,000 miles, 30 kWh per 100 miles, 10% losses, 1,350 kWh per kW, 400 W panels, 18.2¢ per kWh, 28 MPG, $3.20 gas.

Driving energy: 12,000 × 0.30 = 3,600 kWh; with losses, 4,000 kWh a year.
Extra capacity: 4,000 ÷ 1,350 = 2.96 kW, or 8 panels of 400 W (7.4 rounded up).
Cost to charge from the grid: $728 a year. Gas cost it replaces: $1,371 a year.

Second example, an electric SUV in the Houston area: 15,000 miles, 34 kWh per 100 miles, 1,421 kWh per kW (PVWatts for Houston), 400 W panels, 15.5¢ per kWh, replacing a 24 MPG car at $3.00 a gallon.

Charging: 5,667 kWh a year; extra capacity 3.99 kW, or 10 panels.
Grid charging: $878 a year; gas replaced: $1,875 a year.

Mileage compared (default car and location)

Yearly miles	Charging kWh	Extra 400 W panels	Gas cost replaced
8,000	2,667	5	$914
12,000 (default)	4,000	8	$1,371
18,000	6,000	12	$2,057

What your result means

The panel count is in addition to what your home already uses. Add it to the home result in how many solar panels do I need, or raise that tool's coverage to about 120%, then check that the total fits with the roof calculator.

The cost lines show the fuel side. Switching from gas to grid charging saves about $643 a year with the defaults, before any solar. Covering the EV with solar then saves the $728 grid cost too, if exports and imports are credited evenly. Run the full system through the solar savings calculator, and see are solar panels worth it for the bigger decision.

Rules that change the answer

Export credits. Under full retail net metering, daytime solar can offset nighttime charging one for one. Under California's Net Billing Tariff (opens in a new tab), exports earn hourly avoided-cost values, so charging when the sun is up, or storing solar in a battery, matters. Our guide on whether solar batteries are worth it covers that trade-off.
EV rate plans. Many utilities offer time-of-use plans with low overnight prices, which lower the grid cost line.
Utility size limits. Some utilities cap system size based on past usage. A new EV may not show in your history yet, so ask how they handle planned loads.
Federal credits. As of October 2026, the 25D credit no longer applies to home solar completed after December 31, 2025, so extra panels for an EV are priced without it. See how much solar panels cost.

Common mistakes

Using the EPA range figure instead of kWh per 100 miles.
Forgetting charging losses.
Sizing the EV panels but not checking roof space.
Assuming midday solar charges a car that is at work all day, without credits or a battery.
Counting solar EV charging as free while ignoring what the extra panels cost.

Limits of this calculator

This is an educational estimate. It balances energy over a year, uses one electricity rate and one efficiency figure, and ignores seasonal changes in driving and solar output, cold-weather efficiency losses and the cost of the panels and charger. Check your utility's rate plans and export rules before deciding how to charge.

Frequently asked questions

How many solar panels does it take to charge an electric car?

With the defaults, 12,000 miles a year at 30 kWh per 100 miles with 10 percent charging losses needs about 4,000 kWh a year, which takes 8 extra 400 W panels where 1 kW of solar makes 1,350 kWh a year. A larger EV driven 15,000 miles in Houston needs about 10 panels.

Where do I find my EV's kWh per 100 miles?

It is on the EPA fuel economy label and on fueleconomy.gov for each model. Compact cars generally use fewer kWh per 100 miles, while larger SUVs and pickups use more. Your car's trip computer may show miles per kWh instead; divide 100 by that figure to convert.

Do I need a battery to charge my EV with solar?

Not if your utility credits exports at or near retail. The panels can export power by day and you charge at night from the grid, with credits offsetting the cost. Under net billing, where exports earn far less than retail, charging at midday or using a home battery keeps more of the solar value.

Why does the calculator add charging losses?

Some energy is lost between the wall outlet and the car's battery, mainly as heat in the charger and battery. The tool adds 10 percent by default, so 3,600 kWh of driving becomes 4,000 kWh from the wall. Adjust it if your charger reports a different figure.

How much does solar save compared with gas?

With the defaults, the gas car would cost about $1,371 a year in fuel at 28 MPG and $3.20 a gallon, while grid charging costs about $728 at 18.2 cents per kWh. Solar power has no fuel cost once the panels are paid for, but the panels themselves cost money, so compare the extra system price with these yearly figures.

Is it better to add panels now or later for an EV?

If an EV is likely within a few years, adding panels during the original install is usually simpler, since permitting, design and labor are partly fixed costs and the panels will match. Check that your roof has room with the roof calculator, and confirm your utility's size limits.

Should I charge at a particular time of day?

On a time-of-use rate, charging overnight when prices are lowest is usually cheapest from the grid. With solar under net billing, charging midday when panels are producing uses your own power directly. Check your rate plan, since many utilities offer EV-specific plans.

Sources

Checked against these sources. Dates show when each was last reviewed.

Find and Compare Cars (fuel economy and kWh per 100 miles) (opens in a new tab), U.S. Department of Energy and U.S. EPA (fueleconomy.gov) (as ofOctober 2026)
PVWatts Calculator (opens in a new tab), National Laboratory of the Rockies (formerly NREL) (as ofOctober 2026)
Electric Power Monthly, Table 5.6.B (opens in a new tab), U.S. Energy Information Administration (as ofOctober 2026)
Short-Term Energy Outlook: Electricity, Coal and Renewables (opens in a new tab), U.S. Energy Information Administration (as ofOctober 2026)
Net Billing Tariff (opens in a new tab), California Public Utilities Commission (as ofOctober 2026)

Last updated: October 18, 2026How we build our calculators

On this page

25D credit (Residential Clean Energy Credit): A 30% federal tax credit homeowners could claim for solar and batteries they paid for. It ended for expenditures made after December 31, 2025; the IRS counts the expense when installation is completed.
48E credit: A federal business tax credit for clean electricity property. Companies that own leased or PPA systems on homes may claim it, subject to construction deadlines and sourcing rules. The homeowner does not claim it.
Avoided cost: What it would cost a utility to produce or buy the same power elsewhere. Some states pay rooftop exports at an avoided-cost rate, which is far below retail.
Dealer fee: A charge a solar lender takes from the loan, usually built into the amount you borrow so the advertised interest rate looks low. The CFPB has warned these fees can add tens of percent to the price.
Degradation: The slow loss of a panel’s output over time. NREL research puts the median around 0.5% per year, and most panel warranties guarantee roughly 80–90% of original output after 25 years.
Escalator: A yearly percentage increase written into a lease or PPA, often 0–3%. A 2.9% escalator raises the payment by about 100% over 25 years.
FEOC rules: Federal “foreign entity of concern” sourcing limits added in 2025 that a business must meet to claim 48E credits on projects starting construction in 2026 or later.
Interconnection: Your utility’s approval to connect a solar system to the grid. Most utilities require an application before installation and a final permission to operate (PTO) before you turn it on.
Inverter: The device that turns the direct current (DC) from panels or batteries into the alternating current (AC) your home uses. Types include string inverters, microinverters and hybrid inverters that also manage a battery.
Islanding (backup mode): When a solar-plus-battery system disconnects from the grid during an outage and keeps powering your home. Ordinary grid-tied solar without a battery shuts off in an outage for line-worker safety.
kW (kilowatt): A unit of power: how fast electricity is made or used at one moment. Solar system size is quoted in kW of panel capacity (DC). A 7 kW system has panels rated 7,000 watts in total.
kWh (kilowatt-hour): A unit of energy: using 1 kW for one hour. Your electric bill charges you per kWh, and solar output and battery capacity are measured in kWh.
Microinverter: A small inverter mounted under each panel. Shade on one panel affects only that panel, and each panel can be monitored separately. Usually costs a little more than one central string inverter.
NABCEP certification: A voluntary professional certification for solar installers from the North American Board of Certified Energy Practitioners. It is a useful signal, but you should also check state contractor licensing.
NEM 3.0: The common name for California’s Net Billing Tariff, which applies to new rooftop solar customers of PG&E, SCE and SDG&E who applied on or after April 15, 2023. Exports earn hourly values far below retail rates.
Net billing: A billing rule where exported solar earns a credit set by a separate, usually lower, export rate rather than the full retail price. California’s Net Billing Tariff (often called NEM 3.0) is the best-known example.
Net metering: A billing rule where each kWh your panels send to the grid earns a credit equal (or close) to the retail price you pay. Credits offset power you buy later, often rolling over month to month.
Offset: The share of your yearly electricity use that solar is designed to produce. A 100% offset aims to match a year of use; under low export credits a smaller offset can pay back faster.
Payback period: How many years of bill savings it takes to recover what you paid for a system. A shorter payback means a better investment, all else equal.
Peak sun hours: Daily sunlight expressed as the number of hours at full-strength sun (1,000 watts per square meter). Five peak sun hours means the day’s sunlight equals five hours of full sun.
PPA (power purchase agreement): A contract where a company owns the system and you pay for the electricity it produces at a set price per kWh, often rising each year.
PTO (permission to operate): The utility’s final go-ahead to switch on a grid-connected system. Running a system before PTO can violate your utility agreement.
Round-trip efficiency: The share of energy you get back out of a battery compared with what went in. About 90% is typical for home lithium batteries.
Solar lease: A contract where a company owns the panels on your roof and you pay a fixed monthly amount, often with a yearly increase (escalator), usually for 20–25 years.
Specific yield: Yearly energy a solar system produces per kW of capacity, in kWh/kW. It depends on sunshine, tilt, direction and shade. Sunny Southwest roofs often reach 1,600–1,800; cloudier northern roofs 1,100–1,300.
Time-of-use (TOU) rate: An electricity plan where the price per kWh changes by time of day, with the highest prices in late afternoon and evening. Batteries save money by covering those peak hours.
True-up: The annual settlement on a net metering or net billing account. Charges and credits from the past 12 months are totaled, and you pay any balance owed. Leftover credits may be paid out at a low rate or lost.
Usable capacity: The share of a battery’s energy you can actually draw. Spec sheets list it in kWh; compare usable, not total, capacity between batteries.

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