Adding an electric vehicle to a home with solar — or sizing solar for a home that already has one — raises a simple question with a surprisingly concrete answer: how many kilowatt-hours does the car actually need in a year? Unlike a heat pump or a pool heater, an EV's energy use is driven by two numbers you can look up: how far you drive, and how efficiently the car turns electricity into miles. Multiply them, and you have the annual load your solar array, your utility bill, or both must cover.
The short answer for the average American driver is about 4,000 kWh per year — roughly 11 kWh per day, or about 338 kWh per month. The rest of this article shows where that number comes from, how it changes for light and heavy drivers, and why the timing of charging can matter as much as the total.
The two inputs: miles driven and kWh per 100 miles
The U.S. Federal Highway Administration reports that the average American drives about 13,500 miles per year. That figure, cited in RaboResearch's analysis of EV grid impact from FHWA data, is the starting point for every calculation below. Your own mileage is the single biggest variable — a 20,000-mile-a-year driver needs roughly two and a half times the charging energy of an 8,000-mile driver in the same car.
The second input is the car's consumption, expressed as kilowatt-hours per 100 miles (kWh/100 mi) — the number on the EPA fuel-economy label. RaboResearch, citing U.S. driving data, puts typical EV efficiency at roughly 3 to 4 miles per kWh, which converts to about 25 to 33 kWh per 100 miles: compact, efficient models sit near the low end, while larger SUVs and trucks sit at or above the high end. For the worked examples below we use 30 kWh/100 mi as a midpoint — not a claim about any particular model, but a transparent assumption you can replace with your own car's label figure.
One detail worth knowing: the EPA label's kWh/100 mi figure already counts the energy drawn from the AC supply during charging, so charging losses are baked into the consumer-facing number rather than added on top. If you instead start from a battery-side consumption figure, your wall-outlet energy will be somewhat higher — another reason to use the label number when you have it.
The annual math for three driver profiles
The formula is the same in every case: annual miles divided by 100, multiplied by kWh per 100 miles. At the 30 kWh/100 mi midpoint:
- Light driver — 8,000 miles/year: 80 × 30 = 2,400 kWh/year (about 6.6 kWh/day).
- Average driver — 13,500 miles/year: 135 × 30 = 4,050 kWh/year (about 11.1 kWh/day, 338 kWh/month).
- Heavy driver — 20,000 miles/year: 200 × 30 = 6,000 kWh/year (about 16.4 kWh/day, 500 kWh/month).
The full range matters too. At the average 13,500 miles, an efficient car at 25 kWh/100 mi needs 3,375 kWh a year, while a larger, less efficient one at about 33 kWh/100 mi needs roughly 4,500 kWh — a spread of about 1,125 kWh, or more than a quarter of the midpoint figure. Car choice moves the answer almost as much as driving distance does, which is why a single "EVs need X panels" rule of thumb is misleading: the honest answer is always a range built from your miles and your car.
To turn an annual kWh figure into a system size, you need your location's solar production — how many kWh each kilowatt of panels produces in your climate. Our guide to how many solar panels you need walks through that step using monthly usage and sun hours; add the EV's annual kWh to your household usage first, then run the same sizing math on the combined total.
What the EV load costs — and why your electricity price dominates
The dollar cost of charging is simply annual kWh multiplied by your electricity price, and that price varies enormously. As our state electricity price breakdown shows, residential prices differ by more than 2× across U.S. states, so the same 4,050 kWh costs roughly twice as much in a high-price state as in a low-price one. As an illustration only — replace it with your own rate — 4,050 kWh at an assumed $0.17/kWh comes to about $689 a year, or roughly $57 a month. That illustrative rate is not a price quote; your utility's actual rate, including time-of-use tiers if you have them, is the number that matters.
This is also where solar's value proposition for EV owners sharpens. Every kWh your array produces that would otherwise have been bought at your retail rate is a kWh of charging you did not pay the utility for — but only if the accounting works in your favor. Under a full net-metering arrangement, daytime solar exports offset nighttime charging imports nearly one-for-one. Under export rates that pay much less than the retail rate, the match between when you produce and when you charge becomes a real financial question, which brings us to timing.
When you charge matters as much as how much you charge
Most home solar production peaks around midday. Most EVs, however, sit at home overnight — which is exactly when the array is dark. That mismatch has three practical answers, and which one fits depends on your utility's rules:
- Charge during the day when you can. If you work from home, or can schedule charging on weekends and days off, daytime charging lets the car drink directly from the array. Even partial daytime charging — topping up on Saturday and Sunday — shifts a meaningful share of the load onto your own production.
- Use the grid as the buffer. Where net metering or a similar credit arrangement still applies, exported daytime kWh earn credits that offset nighttime charging. Read your utility's current export rules before assuming this — our guide to how net metering works explains the mechanics, and the rules in your state may have changed since it was written.
- Add a battery — but size it for the car, not the house. A home battery can shift daytime solar into nighttime charging, but an EV's daily need of roughly 11 kWh (average driver) is a large share of a typical home battery's usable capacity. Before buying storage for EV charging specifically, compare the battery's cost against the export-versus-import price gap it would actually close — see our pros and cons of solar batteries for that trade-off.
The practical takeaway: do not size a solar array for an EV on annual kWh alone and then assume every kWh is equally valuable. Annual kWh tells you how big the load is; your utility's export rules and your charging schedule tell you how much of it solar can actually displace at full retail value.
A worked example: the average driver, end to end
Pulling it together for the average case: 13,500 miles a year in a car rated at 30 kWh/100 mi needs 4,050 kWh a year. That is 338 kWh a month on top of whatever the household already uses — a load roughly comparable to adding a second major appliance that runs every day. If that driver can charge mostly at home and their utility credits exports at something close to the retail rate, a solar array sized to cover household use plus 4,050 kWh covers the car too. If exports earn far less than imports cost, the same driver should either shift more charging into daylight hours or accept that part of the EV load will still be bought from the grid at night — and size the array for the daytime load it can genuinely serve rather than the annual total on paper.
Either way, the math stays honest only if you start from your own numbers: your annual miles (check your odometer or your last year of service records), your car's label kWh/100 mi, and your utility's actual import and export rates. Swap any of the three and the answer moves — which is exactly why the formula, not a single headline number, is the useful thing to take away.
Sources
- Average annual driving of about 13,500 miles, from U.S. Federal Highway Administration data via RaboResearch, "The rise of electric vehicles in the US: Impact on the electricity grid" — accessed October 24, 2026. See rabobank.com.
- Typical EV efficiency of roughly 3–4 miles per kWh (about 25–33 kWh per 100 miles), from the RaboResearch analysis above, and the EPA label's inclusion of AC charging energy in its kWh/100 mi figure — see EVKX: How EPA EV Range and Efficiency Are Calculated — accessed October 24, 2026.
- State electricity-price variation of more than 2× across U.S. states, using July 2026 EIA data — see our state electricity price breakdown.
Related Guides
- How Many Solar Panels Do I Need for My House? — turn an annual kWh total into a panel count.
- Average Electricity Prices by State (2026) — the kWh price your solar and your EV charging both face.
- Solar Panel Payback Period by State — how the combined household-plus-EV load changes payback.
- Pros and Cons of Solar Batteries — whether storage is the right answer to the day/night mismatch.