Understanding EV fleet charging solar sizing
What size solar system offsets a fleet's charging energy
A 20-vehicle fleet using 30 kWh per vehicle per day needs 600 kWh of daily charging energy, which at 4.8 peak sun hours and an 82% system derate requires a solar system of about 152.4 kW to fully offset. This is a total-energy calculation focused on daily kWh needs, separate from the demand-charge angle covered by battery peak-shaving tools. The fleet depot solar-plus-storage calculator covers that separate demand-charge problem specifically. A related check is the EV charging peak demand charge avoidance tool, which looks at the same question from the solar + ev integration side.
Whether this guarantees the fleet charges entirely on solar
Not directly, since this sizes the system to produce enough energy across a full day to match total fleet consumption, not necessarily aligned to when charging actually happens. If most charging occurs overnight, the solar energy is offsetting consumption on a net annual basis rather than powering the vehicles in real time, which usually requires net metering or battery storage to fully realize. For a different angle on matching production to a variable overnight load, the backup runtime estimator in our battery storage section runs a similar load-matching calculation. If you want a second opinion on the size itself, the solar panel calculator in our System Sizing section works from your roof area and daily load instead of your building type.
How daily charging need varies across fleet types
Daily charging need depends heavily on vehicle type and route length, with light-duty delivery vans typically needing 20 to 40 kWh a day and larger trucks or high-mileage routes needing considerably more. Checking actual telematics or route data for your specific fleet gives a far more accurate figure than a generic estimate, similar to how the battery storage sizing calculator depends on knowing your actual critical load. The Joint Office of Energy and Transportation, a DOE and DOT partnership, offers free fleet electrification technical assistance that can help pull more accurate route and charging data for exactly this kind of sizing question. Incentives change the budget a lot. The federal tax credit calculator in our Rebates & Incentives section can help you estimate the federal credit and rebates before you commit.
Whether to offset the whole fleet or just part of it
Many businesses offset a partial share of fleet charging rather than the full amount, especially if roof or site space is limited relative to what full offset would require. Partial offset still provides meaningful savings and can be scaled up later as the fleet grows or more site space becomes available. The system size by square footage tool can help confirm how much capacity your site can realistically support, and the small business quick size estimator offers a faster ballpark if you just need a rough starting number. The DOE's Alternative Fuels Data Center also maintains a charging infrastructure development checklist that covers the procurement and permitting steps worth planning around once you've settled on a target offset share, and the EV charging peak demand charge avoidance tool covers the demand-charge side that this total-energy calculation deliberately sets aside.