EV charging and solar for business — making them work together

Two things are happening on a lot of business sites at once: the vehicles are going electric, and the roof is going solar. They belong together. Vehicles tend to sit in the car park during the working day — exactly when your panels are generating — so charging them from your own solar is far cheaper than pulling from the grid. But "put chargers in and point solar at them" isn't quite the whole story. Here's how to make the pairing actually work.

Why solar and EV charging fit so well

Solar generates in the middle of the day. A fleet that returns to base, or staff cars parked from 9 to 5, are charging in the middle of the day too. That overlap is the whole point: instead of exporting your midday solar surplus to the grid for a few pence per kWh under the SEG, you use it to charge vehicles, displacing electricity you'd otherwise buy at your full ~28p retail rate.

In other words, EV charging is one of the best ways to lift your solar self-consumption — turning low-value exported units into high-value used ones. It's the rare load that is large, flexible, and naturally daytime. (See south-facing vs east-west for why self-consumption is what really drives commercial solar value.)

What it actually costs per mile

This is the comparison that makes the case, and it's rarely set out plainly. Assume a car managing 3.5 miles per kWh — a reasonable real-world figure:

Energy source	Cost per kWh	Cost per mile
Your own solar (surplus otherwise exported)	~6p opportunity cost	~1.7p
Grid electricity at your commercial rate	28p	~8p
Public rapid charging	~80p	~23p
Petrol equivalent (45 mpg at £1.35/litre)	—	~13.6p

The number that matters is the first row. Charging from solar surplus you'd otherwise have exported costs you only the export income you gave up — around 6p — so roughly 1.7p per mile. That's about a fifth of the cost of grid charging, an eighth of running the petrol equivalent, and a fraction of what public rapid charging costs.

For a van fleet the absolute numbers get larger and the logic identical. Ten vans at 2.5 miles/kWh covering 12,000 miles a year each need about 48,000 kWh. Charged from solar surplus that's roughly £2,900 of foregone export; from the grid at 28p it's £13,400. The gap — around £10,500 a year — is the prize, and it's why fleet electrification and solar are usually one business case rather than two.

The catch is in the words "surplus otherwise exported". That saving is only available on units you were going to export anyway. Charge beyond your surplus and you're buying at 28p like everyone else, which is still cheaper than petrol but nothing like as compelling.

How much solar does a vehicle need?

A useful rule of thumb for scoping before anyone quotes:

• A car covering 12,000 miles a year at 3.5 mi/kWh needs about 3,400 kWh — roughly 3.5 kWp of array in southern England.
• A van covering 12,000 miles a year at 2.5 mi/kWh needs about 4,800 kWh — roughly 5 kWp.

So a ten-van fleet wants ~50 kWp of panels dedicated to it, on top of whatever the building itself consumes. That's a real constraint: fleets are a large load, and "we'll charge the vans off the solar" often turns out to mean "we'll charge two of them". Size the array against the combined building and vehicle demand, or be honest that the fleet will run substantially on grid power.

Slower chargers usually beat faster ones here

The instinct is to specify the most powerful chargers available. For workplace charging paired with solar, that's usually wrong.

• A 7 kW charger over an eight-hour working day delivers 56 kWh — more than enough to fully replenish almost any daily duty cycle.
• A 22 kW three-phase unit does the same job in under three hours, which you rarely need for a vehicle that's parked all day.
• A 50 kW+ rapid DC charger costs several times more, needs serious supply capacity, and will happily consume every unit your array makes and then some.

Slower, more numerous chargers match solar far better: they spread the load across the generating day instead of concentrating it into short high-power bursts your array can't cover. Ten 7 kW sockets draw 70 kW spread over hours; two 50 kW rapids draw 100 kW in spikes that your panels will never match and your supply may not take. Unless you have vehicles on a genuine turnaround requirement, specify many slow rather than few fast.

The bit that catches people out: load management

Here's the technical crux. A bank of EV chargers can draw a lot of power — potentially more than your building's electrical supply can handle on top of everything else. Plug in several fast chargers at once and you can exceed your supply capacity, trip protection, or rack up demand charges that quietly cancel out the fuel saving.

The answer is smart charging with load management (also called load balancing): a system that monitors how much power is available — your spare supply capacity plus whatever your solar is generating right then — and throttles the chargers to fit. Done well, it lets you charge from solar first, draw spare grid capacity second, and avoid an expensive supply upgrade.

The better systems go a step further and offer solar-matched charging, where chargers modulate to track your actual export surplus in real time, so vehicles soak up exactly what would otherwise go to the grid and no more. That's the feature that turns the 1.7p-per-mile figure above from theory into your actual bill. Any competent installer designing solar-plus-EV should build load management in from the start; if it isn't in the proposal, ask why.

Watch the demand-charge interaction too. If your tariff carries a capacity charge based on peak draw, an unmanaged charger bank can set a new annual peak in its first week and cost you for the following twelve months.

The grant worth claiming: the Workplace Charging Scheme

If you're installing chargepoints for staff or fleet use, the Workplace Charging Scheme (WCS) is live and worth claiming. As of 2026 it covers up to 75% of the purchase and installation cost (including VAT), capped at £500 per socket, for up to 40 sockets across your sites. The scheme runs until 31 March 2027.

At the cap, 40 sockets is £20,000 off the chargepoint side of the project — entirely separate from any relief on the solar side, which runs through capital allowances instead.

The conditions to note:

• You must own the property or have landlord consent.
• You need dedicated off-road parking clearly associated with the premises, for staff or fleet — not customer parking.
• You must use an authorised installer (or you can't claim).
• Available across England, Wales, Scotland and Northern Ireland.

Given the March 2027 end date, a project being scoped now should be treating the grant as a reason to move rather than something that will still be there indefinitely.

Solar carports and batteries — the natural extensions

Two pairings worth knowing:

• Solar carports. If your "spare space" is a car park, a solar canopy generates power and shelters the vehicles charging beneath it — a tidy three-in-one, and the groundworks for the canopy and the charger cabling can share a trench. They're the dearest option per kWp, though; we cover the trade-offs in ground-mount vs roof-mount.
• Battery storage. A battery lets you store midday solar and charge vehicles that only return in the late afternoon or evening, smoothing the mismatch between when you generate and when the vehicles are plugged in. For a fleet that's out all day, this is the difference between the pairing working and not working. Whether it pays depends on your pattern — see battery storage and the worked ROI example.

Sanity-check

1. Do vehicles actually park on-site during daylight? If your fleet is out all day and charges overnight, solar's daytime generation won't reach it directly without a battery — and the 1.7p/mile figure doesn't apply to you.
2. Is the array sized for building plus vehicles — roughly 3.5 kWp per car and 5 kWp per van at 12,000 miles a year?
3. Does your electrical supply have headroom for the chargers, and is load management included to avoid an upgrade?
4. Have you specified many slow sockets rather than few rapid ones? Rapids rarely suit all-day parking and fit solar badly.
5. Will the chargers set a new peak on a capacity-charged tariff, and has that been modelled?
6. Are you claiming the Workplace Charging Scheme — staff/fleet parking, authorised installer, before March 2027?

The bottom line

Solar and workplace EV charging are a strong pairing: daytime sun charges daytime-parked vehicles at roughly 1.7p a mile against 8p from the grid and 13.6p in petrol, converting low-value export into high-value self-consumption. The design details decide whether you actually get that: size the array for the vehicles as well as the building, specify many slow chargers over few fast ones, insist on load management with solar matching, and claim the Workplace Charging Scheme while it runs to March 2027. Done together, the two investments reinforce each other. Bolted together carelessly, you get a charger bank that sets a new demand peak and runs on grid power.

To size the solar side against your usage, run the calculator. For the storage question, see battery storage for commercial solar. Monthly intel: the Brief.

General information, not financial advice. Cost-per-mile figures are illustrative and depend on your tariff, vehicle efficiency and how much genuine surplus you have. Confirm WCS eligibility and electrical capacity with an authorised installer.