Solar Powered Heating/Heaters UK

Solar-powered heating can help lower your energy costs and carbon footprint, but it can’t reliably provide you with hot water all year round.

Heating water accounts for a vast portion of your household energy consumption, making solar-powered and solar thermal solutions an attractive option for many UK homeowners.

According to the Energy Saving Trust, hot water accounts for 11% of the average energy bill, and you can save up to £210 annually by using solar water heating instead of electricity.

However, solar heating and the savings you can make will vary throughout the year.

Solar-powered heating can help meet almost all your hot water needs in the summer, but it will struggle in the winter, when demand is highest.

This makes it necessary to consider other options, like heat pumps or immersion heaters, to fill the gap.

To ensure you don’t waste money with unrealistic expectations, it’s critical to explore why plugging heaters directly into solar PV is often inefficient and costly in winter and consider better, smarter alternatives that deliver real savings while aligning with the UK’s climate and energy goals.

Key Takeaways:

Direct heating from solar PV is inefficient in the UK, especially in winter when generation is lowest and demand is highest.
Smarter options include combining PV with a heat pump, PV diverter or solar thermal.
Solar-powered heating solutions are most effective in summer, but all require backup in colder months.
If your goal is space heating, choose PV and a heat pump. If it’s cheaper hot water, add a diverter or solar thermal.

Why PV Doesn’t Efficiently Power a Heater in Winter

According to the Home Insulation and Energy Systems Quality Assured Contractors Scheme (HIES), a standard UK solar PV system of 4 kWp generates roughly 3,400 to 4,200 kWh per year. However, the output is uneven.

The Energy Saving Trust notes that while solar water heating can provide around 90% of your hot water requirements in the summer, this drops to around 25% in the winter.

This means that in July, a system may produce 350-400 kWh, while in December it might generate only 80-100 kWh.

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By comparison, running a single 2 kW electric heater for six hours a day would consume 360 kWh in a single winter month, several times more than the PV system can supply.

This mismatch shows why plugging electric heaters directly into PV rarely works. The power isn’t there in the months when heating is most needed.

Electricity from the grid fills the gap, which means most of the “solar heat” is actually powered by fossil fuel electricity.

In summer, when solar output is high, heating demand is low, so generation is wasted unless you redirect it to other uses.

That’s why direct electric heating with solar energy is usually not a consistent money-saver in the UK climate.

What are Better Ways to Use Solar Powered Heating?

PV + Heat Pump

Pairing solar PV with a heat pump transforms the economics. A heat pump can deliver three to four units of heat for every unit of electricity consumed, thanks to its high Coefficient of Performance (COP).

This means that even limited winter solar generation goes three to four times further than powering resistance heaters.

The amount of money a heat pump paired with solar PV will save you on your fuel bills depends on how much hot water you use and what system you currently use to heat your hot water.

According to Energy Saving Trust, a solar-assisted heat pump can save up to £210 annually when compared to an electric immersion heater if you live in an average-sized, three-bedroom semi-detached home.

You gain an extra benefit if you already have solar panels installed. Each unit of self-consumed solar offsets expensive grid electricity while boosting renewable heating.

This makes PV and heat pumps one of the most practical combinations for reducing both energy bills and carbon emissions.

PV Diverters to Hot Water

If your goal is cheaper hot water rather than space heating, a PV diverter is one of the simplest upgrades.

These devices detect when your solar panels are producing more electricity than your household is consuming. Instead of exporting that surplus to the grid, the diverter redirects it to your immersion heater, warming your hot water cylinder.

In summer, this can cover nearly all of a home’s hot water needs. In winter, output is modest but still contributes.

The key advantage is that it maximises the value of your PV system since hot water effectively stores energy. If you already have a cylinder and immersion element, a PV diverter offers an affordable way to cut bills.

A solar diverter switch installation can add around £800 to your installation costs, and you’ll need to replace your diverter after around 12 years.

Solar Thermal Stores for Solar Powered Heating

Before PV dominated the headlines, solar thermals were the standard way to capture solar energy for water heating.

Thermal energy storage is a way of storing and managing renewable heat until you need it. They work by circulating a heat-transfer fluid through roof-mounted collectors, which then warms water in a storage cylinder.

A purpose-built thermal store can take inputs from several different technologies, provided you design and size it to work with them all.

It might store heat from a biomass boiler, solar water heating system, or a heat pump. A thermal store design can prioritise solar thermal heat above all other sources. This will mean that if solar heat is available, no other heat source will come on.

Thermal stores work very well with solar water heating systems as they allow you to use solar thermal heat for space heating and heating water.

On a sunny day, a solar array may harvest far more energy than is needed for hot tap water alone. Combined with a thermal store that also supplies space heating, this collected heat can be put to good use.

Seasonal Performance and Savings

The key to understanding solar heating is seasonal balance. In summer, solar panels and thermal systems can produce abundant energy, often covering most hot water needs and even driving down grid imports significantly. However, output falls sharply in winter while demand for heating and hot water peaks.

This seasonal mismatch means solar heating should be viewed as a supplement, not a replacement.

For example, a PV diverter might save a household money by reducing immersion heater usage. Additionally, a solar thermal system may cut gas bills by a similar margin for hot water.

Pairing solar with a heat pump has the strongest impact. It reduces running costs by stretching each kWh of solar electricity further, but most households will continue importing significant energy in winter.

The best results come from treating solar as part of a mix that includes efficiency upgrades, insulation, and smart energy use.

Grid Interactions

All solar PV systems in the UK are grid-connected. This means when your panels generate less than you need, the grid automatically tops up the supply.

When your panels produce more than your household is consuming, you can export the surplus under the Smart Export Guarantee (SEG).

This matters for heating because in winter, you will almost always be importing electricity rather than exporting. Therefore, relying on PV alone to power electric heaters is impractical.

The grid will still do some heavy lifting when the panels aren’t generating energy, which involves grid prices and carbon intensity.

You can improve your savings with diverters or heat pumps. Every diverted unit of solar replaces a unit of electricity or gas you’d otherwise pay for.

With heat pumps, each solar unit stretches further, multiplying savings. The grid ensures you always have power, but it also highlights why solar needs to be paired with efficient heating technologies to deliver real impact.

Choosing the Correct Solar-Powered Heating Approach

Your goals and priorities will help determine the best strategy:

Lowering heating bills in winter: Choose PV + heat pump. The efficiency of heat pumps means your solar energy goes 3-4 times further than with resistance heaters.
Reducing hot water costs: If you already have PV, add a PV diverter. If you don’t, consider solar thermal panels.
Summer self-sufficiency for hot water: Either a diverter or solar thermal system can achieve this.
Simple, portable backup heating: Stick with battery storage and small appliances, but don’t expect them to carry your winter load.
Whole-home decarbonisation: Focus on insulation and a heat pump, with PV as a supporting technology.

Such frameworks help you align your investment with realistic outcomes and avoid wasting money on mismatched solutions.

Cost and Carbon Comparison

Here’s a simplified UK comparison of three ways to use solar for heating, using the current Ofgem electricity rate of 25.73 p/kWh (for July-September 2025).

Option	Running Cost per kWh of Heat	Carbon Intensity per kWh Heat	Notes
Direct Electric Heater	25.73 p/kWh	0.20-0.25 kg CO₂	Least efficient: Solar provides minimal actual benefits in winter.
PV Diverter (Immersion)	0-25.73 p/kWh (if surplus exists)	0 if using solar surplus; 0.20-0.25 if grid-supplied	Good for hot water when solar surplus exists. Seasonal.
Heat Pump (COP 3)	8.6 p/kWh	0.06-0.08 kg CO₂	Excellent efficiency by making solar heating significantly cheaper.

Heat pump running costs were estimated using Ofgem’s electricity rate of 25.73 p/kWh ÷ 3 (COP 3) = 8.6 p/kWh heat.

This illustrates why heat pumps dominate when paired with solar. The cost and carbon benefits are far greater per kWh of heat delivered.

Final Thoughts

Solar power is a cornerstone of the UK’s transition to cleaner energy, but when it comes to heating, context is everything. Using PV to run plug-in heaters directly may fail to deliver the savings or comfort you hope for.

Smarter choices include pairing PV with heat pumps for efficient space heating, using PV diverters for low-cost hot water, or exploring solar thermal collectors for households with high water demand.

These solutions may rely on the grid in winter, but they stretch each unit of solar electricity further and cut bills meaningfully.

The best strategy is to treat solar as part of an integrated plan: insulate first, choose efficient heating systems, and then add solar to complement them. When done right, solar heating can lower costs, reduce emissions, and make households more resilient.

FAQs on Solar-Powered Heating

Can Solar Panels Really Heat a House in the UK?

Not directly. UK solar output is lowest in winter when heating demand is highest.

Panels can support heating when paired with a heat pump or immersion diverter, but they can’t replace a full heating system on their own.

Is It Worth Using Solar Panels for Hot Water?

Yes, with the right setup. Solar for hot water is worthwhile if you have a high hot water demand, a suitable tank, and realistic expectations about winter performance.

Combining solar with a diverter or heat pump can help cut gas or electricity bills for hot water over the year.

What’s the Most Cost-Effective Way to Use Solar for Heating?

Pairing solar with a heat pump gives the best savings, cutting heat costs to around 8.6p per kWh (vs 25.73p for direct electric heaters) and lowering carbon emissions by up to two-thirds.

Sources and References

Energy Saving Trust – Solar water heating
HIES Consumer Code – Solar Panels
Energy Saving Trust – Solar-assisted heat pumps
Energy Saving Trust – Solar panels
Ofgem – Energy price cap explained