Solar Panels & Electric Heating: Can You Heat for Free?

The fundamental challenge: heating demand peaks in winter, solar generation peaks in summer.

4kW system monthly generation vs heating demand:

| Month | Solar Output | Heating Need | Gap | |-------|-------------|-------------|-----| | January | 100 kWh | 1,200 kWh | –1,100 kWh | | February | 150 kWh | 1,000 kWh | –850 kWh | | March | 300 kWh | 800 kWh | –500 kWh | | April | 420 kWh | 400 kWh | +20 kWh | | May | 500 kWh | 100 kWh | +400 kWh | | October | 220 kWh | 500 kWh | –280 kWh | | November | 120 kWh | 900 kWh | –780 kWh | | December | 80 kWh | 1,200 kWh | –1,120 kWh |

*Heating demand based on average 3-bed home with electric heating (~8,000 kWh/year)*

In the 6 coldest months, solar covers approximately 10–15% of heating electricity demand. The remaining 85–90% must come from the grid.

Key insight: Solar is excellent for electricity (lighting, appliances, devices). For heating, it is a supplement, not a replacement — unless paired with a heat pump.

Source: PVGIS; Energy Saving Trust heating demand data.

If you have a hot water cylinder (common with electric heating systems), a solar diverter is an excellent investment:

What it does: Automatically routes surplus solar electricity to your immersion heater, heating your hot water for free instead of exporting to the grid.

Products: - iBoost+ (£200–£350 installed) - Eddi by Myenergi (£350–£500 installed)

Value: Hot water heating costs approximately £200–£400/year for an electrically heated home. A solar diverter can reduce this by 40–60% in summer and 10–20% in winter.

Payback: 1–2 years for the diverter itself. One of the fastest-payback solar accessories.

This does not heat your rooms — but it does reduce your hot water bill significantly.

Source: Product manufacturer data; installer pricing.

If you currently heat with direct electric (storage heaters, panel heaters, or electric boiler), the most impactful upgrade is:

Solar panels + air source heat pump:

- A heat pump converts 1 kWh of electricity into 3–4 kWh of heat (COP 3–4) - This means your solar panels effectively produce 3–4x more heating than direct electric - In December, 100 kWh of solar powers 300–400 kWh of heat from the pump - The £7,500 BUS grant reduces heat pump cost significantly

Direct electric heating vs heat pump comparison:

| System | Annual Heating Cost | with Solar Reduction | |--------|-------------------|---------------------| | Direct electric (storage heaters) | £2,000–£2,500 | £1,700–£2,200 | | Direct electric + solar diverter | £1,800–£2,300 | £1,500–£2,000 | | Air source heat pump (grid) | £600–£900 | N/A | | Air source heat pump + solar | £300–£600 | Best option |

Solar + heat pump costs £300–£600/year for heating vs £2,000–£2,500 for direct electric. The savings are transformational.

Source: Energy Saving Trust; BUS grant terms; Ofgem Q1 2026.

If a heat pump is not feasible (listed building, space constraints, budget), here is how to maximise solar for electric heating:

1. Install the largest solar system your roof allows — more panels = more winter generation 2. Add a battery (10kWh+) — store daytime solar for evening heating 3. Install a solar diverter — free hot water from surplus solar 4. Use time-of-use tariffs — charge battery at 7.5p/kWh overnight (Octopus Go), use for heating during expensive peak hours 5. Improve insulation — reduce heat loss so less electricity is needed. Loft insulation, draught-proofing, and double glazing have the biggest impact. 6. Use infrared panels where possible — they heat objects directly (more efficient than convection heaters for spot heating)

The combination of solar + battery + smart tariff + insulation can reduce electric heating costs by 30–50%, even without a heat pump.

Source: Energy Saving Trust; installer recommendations.