Solar + EV integration

EV charging load addition calculator

An EV changes your solar math. Add your daily driving, efficiency, panel specs, and sun hours to see exactly how many extra panels it needs.

Your EV and system numbers

1 Project details Optional
Shown on your exported report. Leave blank to skip.
2 Your driving
Use your typical commute plus errands, not a rare long trip.
Count every day the car actually moves, including weekends.
Pick the closest match, or enter your own EPA-rated figure below.
Find this on the EPA Monroney label or fueleconomy.gov. Overrides the dropdown if filled in.
3 Charging setup
Charging losses come from AC-DC conversion and cable resistance.
Extra charge held in reserve for unplanned trips or range loss.
4 Your solar system
Most residential panels sold today are 350 to 440 watts.
Check NREL's PVWatts for a US address or NRCan's solar maps for Canada.
Combines inverter loss, wiring loss, dust, and temperature derate.
Leave blank if you're sizing a brand new system, not adding to one.

How it works

Three steps to your added panel count

Step 1

Enter your driving and vehicle efficiency

Use your real average daily mileage, not a best case. Pick your vehicle type or type in the exact EPA figure from fueleconomy.gov for the most accurate result.

Step 2

Choose your charger type and system details

Level 1 and Level 2 chargers waste different amounts of power as heat during conversion. Match your panel wattage and derate factor to your actual or planned equipment, listed on the solar panel calculator.

Step 3

Check the total against your roof space

Add the new panel count to your existing array and confirm your roof has room using the usable roof area calculator, especially on a roof with limited south-facing space.

Understanding your EV's added solar load

Why EV charging load is different from household load

A typical US home uses around 29 kWh a day for everything else combined, and that number barely changes week to week. EV charging load is spiky and tied directly to how much you drive, so a household that skips a weekend trip uses meaningfully less energy that week. This calculator averages your weekly driving into a daily figure, the same way a utility bill averages seasonal swings, so the panel count reflects a realistic year-round need rather than a single heavy-driving day.

Why charging losses change the panel count more than people expect

The energy stored in your EV's battery is always less than the energy your solar system generates, because AC to DC conversion, cable resistance, and onboard charger inefficiency all take a cut. A Level 1 charger running off a standard outlet loses around 8%, a Level 2 home charger loses closer to 12%, and DC fast charging used occasionally at home loses less per session but isn't typical for daily solar-matched charging. Skipping this step under-sizes your array by roughly one panel for every 8 to 10 panels in the base count, worth double-checking against the quick 5 minute system size estimator.

Vehicle type matters as much as miles driven

A midsize sedan and a full-size pickup can cover the same 30 miles a day but need very different amounts of energy to do it. EPA-rated efficiency for EVs ranges from around 24 kWh per 100 miles for the most efficient sedans up to 48 kWh per 100 miles or more for large electric trucks. Check the exact figure for your model on fueleconomy.gov before finalizing a purchase decision, since the dropdown estimate here is a category average, not a specific trim.

Sizing for a household with more than one driver

If a second EV is planned within the next few years, it's usually cheaper to add its expected load to this calculation now than to install a second array later, since a second installation means a second round of permitting, labor, and interconnection paperwork, the same overhead the total cost including financing fees calculator accounts for. The two EV household calculator and multi-vehicle sizing tool handle more than one vehicle directly.

Where to go from here

Take your added panel count to the EV solar payback calculator to see the return on the added array cost, or to the EV charger sizing tool to confirm your electrical panel and charger can support the added load safely.

Questions

Frequently asked

Most single-EV households need 5 to 9 extra 400-watt panels, or roughly 2 to 3.5 kW of added system size. A driver covering 30 miles a day in a Tesla Model 3, at 25 kWh per 100 miles with 400-watt panels and 5 peak sun hours, needs about 6 extra panels.

The energy your solar system must generate is higher than what actually lands in the battery, because AC to DC conversion and cable resistance waste roughly 10 to 15% of the power along the way. A Level 2 home charger typically runs at 88 to 92% efficiency, so sizing off battery kWh alone undercounts your real panel need.

Yes, since solar sizing is based on average daily energy use across the full year, not just the days you drive. A commuter who drives 5 days a week instead of 7 needs about 29% fewer added panels for the same per-trip mileage.

If a second EV is likely within 3 to 5 years, add its expected daily miles now rather than resizing your array later, since a second installation means a second round of permitting and labor. Add 20 to 40% to your current EV load as a placeholder if the second vehicle isn't chosen yet.

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Take your panel count further

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