Solar, heat pumps and EVs: the all-electric home

Solar makes more financial sense the more of your own electricity you use, and nothing raises your use like a heat pump or an EV. Electrify your heating and your car, and the panels on your roof start working a lot harder, because more of what they make gets used at home instead of exported cheaply. Here's how the three fit together, and where the maths helps or doesn't.

Why electrifying changes the solar maths

An average UK home uses roughly 2,700 to 3,500 kWh of electricity a year. Add a heat pump and you might add another 2,500 to 4,000 kWh; add an EV driven 8,000 to 10,000 miles and that's another 2,000 to 3,000 kWh at around 3.5 to 4 miles per kWh. Your electricity demand can double or more. Because solar pays best when you use it live rather than export it (the logic is in is solar worth it), a bigger electricity appetite means more of your generation is worth the full ~25p import rate instead of the ~15p export rate.

Solar and a heat pump

A heat pump runs all year but works hardest in winter, exactly when solar output is lowest. So solar won't power most of your January heating directly, and you shouldn't oversize an array expecting it to. What it does do is lift your annual self-consumption and cover a real share of shoulder-season and summer hot water. A heat pump delivers around three units of heat per unit of electricity (a coefficient of performance near 3), so each solar kWh it uses stretches further than it would in a resistive heater.

The strong pairing is solar, a battery, and a cheap night tariff: store cheap or self-generated power and run the heat pump off it through the evening. Worth knowing separately, heat pumps carry their own 0% VAT and, in England and Wales, a Boiler Upgrade Scheme grant of £7,500 toward installation.

Solar and an EV

This is the best match of the three. A 7kW home charger can absorb roughly what a 4 kWp array produces at midday, so if you're home in the day, solar can cover a meaningful chunk of your miles for free. If you're out, a smart EV tariff such as Intelligent Octopus Go drops overnight electricity to around 7p per kWh; you charge the car cheaply at night and let solar handle daytime household load and top-ups. Either way the EV behaves like a large, wheeled battery that soaks up energy you'd otherwise sell cheaply.

Sizing for an all-electric home

With more load to absorb, you can justify a larger array, often closer to your roof's full capacity, and a larger battery, because there's somewhere for the extra capacity to go each day. A 3 to 4 kWp system suits a modest home; an all-electric household with a heat pump and an EV can make good use of 5 to 6 kWp or more, paired with 10 kWh of storage rather than 5. Whether the battery earns its keep is still its own decision, set out in do I need a battery.

A worked example

Take a four-bedroom home that's gone fully electric: a heat pump, one EV, and no gas. Its electricity demand might sit near 9,000 to 11,000 kWh a year, roughly three times a typical home. A 5 to 6 kWp array generating around 5,000 kWh could cover about half of that on paper, though not evenly: a surplus in summer, a shortfall in deep winter. Add a 10 kWh battery and a cheap night tariff, and the household self-consumes most of what the panels make while filling the winter gap with off-peak grid power at around 7p rather than 25p. The result isn't energy independence, it's a much larger slice of demand met cheaply.

What winter really looks like

It's worth being honest about the seasons. A UK array makes the bulk of its output between March and October; December and January might deliver under a fifth of a sunny month. For an all-electric home that's exactly when heating demand peaks, so the grid does the heavy lifting in winter however many panels you fit. The case for solar in an electric home isn't winter heating. It's the large summer and shoulder-season surplus, plus the year-round EV and hot-water load the panels can serve directly.

Does the order matter?

You don't have to do everything at once. Solar is worth modelling now, and its value grows as you electrify, so installing panels first and adding a heat pump or EV later is a reasonable path. The one thing to get right up front is the inverter: if a battery is likely, a hybrid inverter saves a second one later, a point covered in how to read a quote.