Britain's third heatwave of the year has left people sweltering and sent interest in air conditioning soaring.

However, many worry not just about the cost of installing air con but also of running it, so could combining it with solar panels help cool your home for free?

The short answer is yes. During sunny spells, a typical UK rooftop solar system can provide enough electricity to run a whole-home air conditioning system for several hours without drawing from the grid.

Solar panels and air conditioning have very similar seasonal patterns, making them complementary partners. Solar panels installed on your roof work by capturing sunlight and transforming it into usable, renewable electricity to power your home.

The hotter and sunnier the weather becomes, the harder air conditioning has to work. But those are also the conditions in which solar panels generate the most electricity.

Without solar, running air conditioning means paying for every unit of electricity consumed. But new data has highlighted how much free air conditioning use solar panels can generate.

During last month’s heatwave, a typical UK rooftop solar installation generated enough electricity to power around five hours of air conditioning in one day. 

Researchers at clean energy think tank Ember estimate that on June 21 and 22, these systems produced around 15kWh of electricity each day.

This is equivalent to five hours of electricity demand from a 3kW whole-home air conditioning system.

Kilowatt-hours (kWh) are a unit of energy equal to the amount of electricity used by a 1,000-watt appliance running for one hour.

The analysis was based on a typical UK rooftop solar installation. Most UK homes have a system of around 4kW to 5kW, which usually consists of around 10 to 12 modern 400W solar panels, although the amount of electricity generated depends on factors including sunshine, roof orientation and shading.

The cost of a solar panel system depends on its size and how it is installed. A professionally installed 4kW to 5kW system suitable for many UK homes typically costs several thousand pounds, while smaller systems and DIY kits can be significantly cheaper.

As the UK experiences more frequent hot spells, the Climate Change Committee previously stated that almost a quarter of UK buildings could require active cooling in a world that's 2C warmer.

For homeowners considering installing air conditioning, or an air-to-air heat pump that can also cool homes, solar could increasingly become part of the financial calculation.

At today's average electricity price of around 26.11p per kWh, generating 15.2kWh yourself would save roughly £4 compared with buying the electricity from the grid.

If similar levels of sunshine continued across a week-long hot spell, that could amount to around £28 worth of electricity.

Based on this information, your solar panels could generate enough electricity to run a 3kW air conditioning system for around five hours a day during peak summer sunshine.

Of course, these savings won't be possible every day. Solar panels generate the most electricity during long, sunny summer days, meaning households that use air conditioning while the sun is shining are likely to benefit the most.

Those cooling their homes later in the evening or overnight are more likely to need electricity from the grid, unless they also have a home battery to store excess solar power.

Even so, the figures show why solar panels and air conditioning are increasingly seen as complementary technologies. As hotter summers become more common, generating electricity at the same time cooling demand is at its highest could help households reduce their energy bills during future heatwaves. 

Meanwhile, households with solar panels often export excess electricity back to the grid using a special export tariff. For example, the Outgoing Octopus tariff from the UK's biggest home energy supplier pays 12p per kWh for units exported.

As with many other products, it’s important to compare the options available to secure the best deal. Some certified retailers include Wickes Solar or Octopus Energy.

The average household in the UK, consisting of three to four people in a three-bed home, will need a solar panel system of around 4kW to 5kW to meet their energy needs.

Most installed systems are between 2kW and 5kW, according to the renewable energy information website, the Renewable Energy Hub.

Installers usually discuss the cost in terms of cost per watt installed, which could range between £1.30 and £2.20, according to battery technology firm EcoFlow.

For an average system of around 4.5kW, this could bring the cost to as much as £9,900.

The cost of air conditioning also varies. However, a fully installed, multi-room air conditioning system in the UK typically costs between £3,000 and £6,500 or more for a standard family home.

There are also many different places to buy aircon such as B&Q, British Gas, or major retailers like AirCon Direct or Air Con Centre.