Solar EV Charging at Night: What Overnight Fleets Can Do Instead

Solar panels produce nothing after dark, so vehicles that are parked and charged only overnight get almost none of their energy from the panels. In an hour-by-hour simulation of a London array, only about 3% of the yearly output falls in an 18:00–07:00 window, so even an array as large as the vehicles’ yearly demand supplies about 3% of their charging. For a twenty-van depot with a 100 kW array and vans parked overnight only, the solar share was about 2%. If that is your fleet, the question is not how to add more panels. It is what to do instead.

Why the gap is structural

An array’s output peaks around midday and in summer. Vehicles that return at 18:00 and leave at 07:00 are plugged in during the hours with the least sun. Adding panels raises the daytime output but not the share that falls in the window, and any output the site does not use is exported at a low price, assumed here at 5p per kWh. That is why an overnight fleet’s array pays back in about 23.2 years when judged only on the vehicles it charges, against about 7.8 years for a workplace fleet that follows the sun.

Four things to do instead

1. Charge from the grid at the cheapest hours. For private charge points in scope of the Smart Charge Points Regulations 2021, the default charging hours must be outside the peak periods the regulations define as 8am to 11am and 4pm to 10pm on weekdays, so a depot charger is built for off-peak charging. Whether your electricity contract rewards it is a matter for your supplier; ask for a time-of-use price. The OCPP chargers guide sets out what those regulations require.
2. Use the building. If the site has weekday daytime demand, put the array’s money into the building’s consumption, where an array whose output is all used pays back in about 5.3 years, and charge the vehicles from the grid at night.
3. Move some charging into the day. Vans that return for a break, a lunch top-up or a mid-shift turnaround can take a daytime top-up, and a controller can fit it to the sun. The load-management guide explains how.
4. Price a battery separately. A battery can carry daytime surplus into the evening and overnight. The model on this site does not include one, so any claim of savings must come from a quote that prices the battery on its own and shows what it adds. Do not accept a bundled figure.

The supply still matters

Overnight charging concentrates demand into a few hours. Twenty vans doing 18,000 miles a year at 0.40 kWh a mile need about 46 kW across a 12-hour window, against 140 kW if every 7 kW socket ran at once. Load management turns the second number into the first, which is often the difference between a supply upgrade and none. The fleet depot guide works through the example and the grid connection guide covers the network operator.

When solar does fit an overnight fleet

Only with storage, with a building that uses the output, or with a change to the parking pattern. Otherwise the honest answer is that overnight vans are a grid-charging problem. For a depot with daytime dwell, the position reverses: the same array supplies about 31% of the vans’ energy. The solar powered EV charger guide and the calculator let you test your own pattern, and the van charging cost comparison shows what the grid-only option costs.

Sources: EU JRC PVGIS 5.3 hourly series 2005–2023; The Electric Vehicles (Smart Charge Points) Regulations 2021, S.I. 2021/1467, regulation 10 — legislation.gov.uk; DESNZ Solar PV cost data 2025/26. The 0.40 kWh a mile van figure and the 5p export price are assumptions. Checked 20 October 2026.