Solar panels and air con: what UK homeowners need to know

UK summer temperatures hit 40°C for the first time in 2022. Since then, air conditioning sales have risen 300% year-on-year, according to industry data. The question on many homeowners’ minds: can solar panels make running those units effectively free?

As reported by This is Money, the idea is seductive: solar panels generate electricity when the sun shines brightest, exactly when you need cooling. But the reality is more nuanced.

Who qualifies, and who doesn’t

The typical UK 3-bed semi uses about 2,700 kWh annually. A 4kW solar system generates around 3,400 kWh per year in southern England, less in Scotland. A 3.5kW air conditioning unit running 8 hours daily on a hot day consumes about 28 kWh. That’s more than a typical household’s total daily electricity use.

So ‘free’ only works if you have a large enough system. Homes with south-facing roofs, minimal shading, and 6-8 panels (2.4-3.2 kW) can cover daytime cooling for a single room. For whole-house cooling, you’d need 12+ panels (4.8 kW+) plus a battery to store excess generation for evening use.

Ofgem’s data shows the average solar-plus-battery system costs £7,000-£12,000 installed. Air conditioning installation adds £2,000-£5,000 for a multi-room setup. The total: £9,000-£17,000. Payback depends on electricity prices and usage patterns.

What it costs a typical 3-bed semi

Let’s run the numbers. A 4kW solar system generates about 8 kWh on a cloudy June day, 20 kWh on a sunny one. A 3.5kW air con unit running 6 hours uses 21 kWh. On sunny days, solar covers it. On cloudy days, you draw from the grid at 24.5p/kWh (October 2024 price cap).

Energy Saving Trust estimates that solar panels can cut a household’s electricity bill by £270-£640 annually. If you’re running air conditioning for 30-60 days a year, the cooling portion of that saving is £100-£250. Not free, but a meaningful reduction.

With a 5kWh battery (costing £2,000-£3,000 extra), you can store midday solar generation for evening cooling. That pushes self-consumption from 30% to 60-70%, making the system economics work better.

But the catch is summer generation patterns. Solar output peaks at 1pm; air con demand peaks at 5-8pm when people return home. Without battery storage, you’re exporting cheap power at 15p/kWh and buying back at 24.5p.

EPC impact and property value

Solar panels can lift an EPC rating from D to C or C to B, depending on the property. That’s worth £5,000-£15,000 in property value, according to Nationwide’s 2023 analysis. Air conditioning alone doesn’t improve EPC, it’s a cooling technology, not an efficiency measure.

The most cost-effective route: install solar panels first, then consider air conditioning only if you have surplus generation. If your solar system already covers 80% of your annual electricity, adding cooling load may push you back to grid dependency.

Government grants under the Boiler Upgrade Scheme don’t cover air conditioning. But the 0% VAT on solar panels (until 2027) applies, saving £1,200-£2,000 on a typical installation.

What the smart money does

For most UK homeowners, the priority should be passive cooling first: loft insulation (saves £300/year), reflective roof coatings (£500-£1,000), and external blinds (£200-£600 per window). These reduce cooling load by 30-50% before you even switch on a unit.

If you do want air conditioning, choose a unit with a high SEER rating (7+ for Europe, 10+ for premium models) and pair it with solar panels and battery storage. The combined system can achieve 70-80% self-sufficiency on summer days.

But don’t expect free cooling. The physics doesn’t work that way. What you get is cheaper, greener cooling, and a home that’s more resilient to the hotter summers ahead. Act before April 2025, when the next price cap review may push electricity costs higher.