Is Solar EV Charging Worth It? A Break-Even Test for Business
Published 14 October 2026 · Commercial Solar EV Editorial
Solar EV charging is worth it for a business when its vehicles are parked in daylight or when the building uses the rest of the array’s output — and often not otherwise. That is not what most guides say, so this post shows the test: the same published prices and the same hourly solar model as the calculator, with the payback worked out for four parking patterns. The answer changes by a factor of three depending on when the vehicles are at the site.
The prices that decide it
- Grid electricity: 24.14p per kWh, the Q1 2026 average non-domestic price including the Climate Change Levy (DESNZ).
- Export: 5p per kWh, our assumption; use your own tariff.
- Solar installed cost: £1,167 per kW, the DESNZ 2025/26 mean for non-domestic 10–50 kW systems; larger arrays may cost less per kW.
- Solar output: 904 kWh per kW a year in London (PVGIS hourly series, 2005–2023, 10° south-facing); other cities in the calculator.
At those prices, an array whose output the building uses entirely pays back in about 5.3 years before tax relief — ordinary commercial solar economics. Vehicles change that only through when they take the energy.
The break-even test
Take a London array and ask: if the only thing it does is charge the vehicles, with whatever the vehicles cannot use exported at 5p, how long does it take to repay its cost? That is deliberately conservative — it gives the building no credit — and it isolates the vehicles’ contribution.
| Parking pattern and control | Array size (× demand) | Solar share of vehicle energy | Payback if only the vehicles use the array | Payback if the building uses every kWh |
|---|---|---|---|---|
| Workplace 09–17, solar-following | 0.5× | 30% | 7.8 years | 5.3 years |
| Workplace 09–17, solar-following | 1× | 56% | 8.2 years | 5.3 years |
| Workplace 09–17, plug-in on arrival (10 kWh/day) | 0.5× | 7% | 17.1 years | 5.3 years |
| Workplace 09–17, plug-in on arrival (10 kWh/day) | 1× | 13% | 17.1 years | 5.3 years |
| Daytime depot 10–16, solar-following | 0.5× | 25% | 8.9 years | 5.3 years |
| Daytime depot 10–16, solar-following | 1× | 49% | 9.0 years | 5.3 years |
| Overnight depot 18–07, any control | 0.5× | 1% | 23.2 years | 5.3 years |
| Overnight depot 18–07, any control | 1× | 3% | 23.2 years | 5.3 years |
Four things come out of the table.
- Parking hours decide the answer. A workplace fleet parked 09:00–17:00 with solar-following charging repays the array in about 7.8 years at an array half the size of its demand. Vehicles parked overnight repay it in about 23.2 years, because very little of the array’s output falls in their window and the rest is exported at 5p.
- Control matters as much as the array. The same workplace fleet with chargers that start on arrival takes about 17.1 years. The hardware is the same; the specification is different.
- Size matters little. Doubling the array from 0.5× to 1× the vehicles’ demand barely moves the payback, because each additional kW earns roughly what the previous one did.
- A building that uses the output beats all of them. The last column, 5.3 years, applies whatever the vehicles do. If your site has weekday daytime demand, the array is worth building for the building, and the vehicles are a bonus.
When solar EV charging is worth it
- Vehicles parked on site during working hours, and chargers that follow the sun. Workplaces, business parks and depots whose vans sit in the yard between runs all qualify.
- A building with daytime demand. Then the array pays back on the building’s consumption, and charging at the same site adds to the share used on site.
- Vehicles currently using public chargers. Moving them to the site’s own supply saves about 55% to 69% of their energy cost before any solar is added — see the cost-per-mile comparison.
When it is not
- Overnight-only fleets with no daytime building load. About 3% of an array’s output falls in an 18:00–07:00 window, so the array earns mostly export income. Charge from the grid, ideally on a cheap overnight tariff, and put solar money into a battery only if a quote shows it pays.
- Sites where the array would be too small to follow. A charger cannot follow a surplus below 6 A per phase — 1.4 kW single-phase, 4.1 kW three-phase — so one or two chargers and a small array use less solar than the model shows unless the charger can switch phases. See the engineering behind solar charging.
- Projects timed against the deadlines. The Workplace Charging Scheme and the chargepoint first-year allowance for companies both end on 31 March 2027; the capital allowances guide sets out how they interact with the solar.
What the test leaves out
Capital allowances, grants, finance costs, maintenance and inverter replacement are all outside it, as are building load, batteries and weekends. They change the paybacks above but not the ranking between parking patterns. London’s yearly output ranged from 861 to 978 kWh per kW between 2005 and 2023, so a single year can differ by several per cent. If you want the test run on your own fleet and array, the calculator takes your numbers; the solar EV charging FAQs cover the surrounding questions.
Sources: DESNZ Quarterly Energy Prices table 3.4.2 (Q1 2026); DESNZ Solar PV cost data 2025/26; EU JRC PVGIS 5.3 hourly series 2005–2023; Zapmap Price Index, August 2026. Checked 14 October 2026.