Solar Panels & Heat Pumps Together: Complete Guide

Solar panels generate free electricity. Air source heat pumps (ASHPs) convert 1kWh of electricity into 3–4kWh of heat (known as the Coefficient of Performance, or COP). Together:

1. Spring/Summer/Autumn: Solar generates more than enough for the heat pump (which runs less because heating demand is lower). Surplus charges battery or exports. 2. Winter: Solar generates less, but the heat pump still runs efficiently. Grid electricity + overnight cheap tariff rates fill the gap. 3. Hot water year-round: The heat pump heats your cylinder; solar powers the pump. In summer, solar covers nearly all hot water heating costs.

The synergy: Without solar, a heat pump still saves money vs gas — but you pay grid rates for the electricity. With solar, much of that electricity is free, dramatically improving the ROI of both systems.

Source: Energy Saving Trust; MCS heat pump performance data.

Installation costs: - Solar panels (5kW): £6,500–£9,500 - Air source heat pump: £8,000–£14,000 - BUS grant (heat pump): –£7,500 - Total after grant: £7,000–£16,000

Annual running costs comparison:

| Heating System | Annual Cost | vs Gas Boiler | |---------------|-------------|---------------| | Gas boiler (old) | £1,400–£1,800 | Baseline | | Gas boiler (new) | £1,100–£1,400 | –£300 | | ASHP (grid electricity) | £800–£1,100 | –£500 | | ASHP + solar (no battery) | £400–£700 | –£900 | | ASHP + solar + battery | £200–£500 | –£1,200 |

Combined annual savings (solar + heat pump vs gas boiler): - Without battery: £900–£1,400/year - With battery: £1,200–£2,000/year

*These include both heating savings AND electricity savings.*

Source: Ofgem Q1 2026; Energy Saving Trust heat pump running costs; BUS grant terms.

A heat pump increases your electricity consumption significantly — you need a larger solar system to compensate:

Without heat pump: - Home electricity: ~3,700 kWh/year - Recommended solar: 4kW (10 panels)

With heat pump: - Home electricity: ~3,700 kWh/year - Heat pump electricity: ~3,000–4,000 kWh/year - Total: ~6,700–7,700 kWh/year - Recommended solar: 6–8kW (15–20 panels)

A 6–8kW system generates 5,600–8,400 kWh/year — covering 70–100% of combined electricity needs annually (though not always at the right time of day or season).

Key insight: The heat pump uses most electricity in winter when solar generates least. A battery + time-of-use tariff (like Octopus Go at 7.5p/kWh overnight) bridges this gap cost-effectively.

Source: PVGIS; typical ASHP electricity consumption data.

The UK government's Boiler Upgrade Scheme provides £7,500 toward the cost of an air source heat pump (increased from £5,000 in October 2025).

Eligibility: - Your property must have an EPC certificate (does not need to be a specific rating) - Replacing a fossil fuel heating system (gas, oil, LPG, electric storage) - The heat pump must be installed by an MCS-certified installer - Property must be in England or Wales (Scotland has separate schemes)

How it works: - Your installer applies for the grant on your behalf - The £7,500 is deducted from the installation cost - You pay the remaining balance (typically £500–£6,500 depending on system)

Combined with solar panels at 0% VAT, the total cost of a solar + heat pump system is remarkably affordable: - Solar (5kW): £8,000 - Heat pump: £11,000 – £7,500 grant = £3,500 - Combined: £11,500

Source: UK Government BUS scheme terms; Ofgem BUS administration.

If your gas boiler is still working: Install solar first. It reduces electricity costs immediately, and you can add a heat pump when the boiler needs replacing.

If your gas boiler needs replacing soon: Install both at the same time. This is cheapest (shared scaffolding, one electrical upgrade) and lets you size the solar system for the heat pump's electricity demand.

If you already have solar: Add a heat pump whenever your boiler needs replacing. Consider upgrading your solar system (adding panels) at the same time to cover the increased electricity demand.

If you already have a heat pump: Add solar to reduce the electricity cost of running the heat pump. Even a 4kW solar system significantly cuts heat pump running costs.

Source: Energy Saving Trust phased installation guidance.