Export Tariff and Heat Pumps: Using Solar Surplus

If you have solar panels and a heat pump, you face a simple but important question every sunny day: what should you do with the surplus electricity your panels generate? You can export it to the grid and receive a modest payment, or you can use it to power your heat pump and generate free heating or hot water. The economics overwhelmingly favour using it yourself — and this article explains exactly why and how.

Understanding the relationship between solar PV and your heat pump is key to getting the most from both investments. The export tariff is not bad — it is just that self-consumption is so much better.

What Is the Export Tariff?

When your solar panels generate more electricity than your home is using, the surplus flows back into the national grid. The Smart Export Guarantee (SEG) requires electricity suppliers to pay you for this exported electricity, though the rate varies considerably between suppliers.

Current export tariff rates (2026)

Octopus Energy (fixed export): 4-7.5p per kWh
Octopus Agile Outgoing: Variable, averaging 5-10p but can spike higher
British Gas: 3-5p per kWh
EDF: 3-5p per kWh
E.ON: 3-4.5p per kWh
Scottish Power: 3-4p per kWh

The important number to remember: you typically receive 4-7p for every kWh you export. Now compare that to what it costs you to buy electricity from the grid: approximately 24p per kWh. There is a massive asymmetry. Every kWh you use yourself saves you 24p. Every kWh you export earns you 4-7p. Self-consumption is worth three to six times more than exporting.

The Heat Pump Multiplier: Why Self-Consumption Is Even Better Than It Looks

The comparison above understates the advantage of self-consumption when you have a heat pump. Here is why.

When your heat pump uses 1 kWh of solar electricity, it does not generate 1 kWh of useful heat. Thanks to the coefficient of performance (COP), it generates 3-4 kWh of heat. So that single kWh of solar electricity — which you could have exported for 5p — instead produces 3-4 kWh of heat that would have cost you 72-96p to produce using grid electricity (at 24p per kWh divided by a COP of 3.5).

Let us put that in stark terms:

Export 1 kWh: Earn 5p
Use 1 kWh in heat pump: Save 24p on electricity, equivalent to 72p+ worth of heating

Using solar surplus in your heat pump is roughly 5 to 15 times more valuable than exporting it, depending on your COP and tariff rates.

Strategies for Maximising Solar Self-Consumption

Knowing that self-consumption beats exporting is one thing. Actually capturing that surplus solar electricity is another. Here are the most effective strategies, ranked by impact.

1. Schedule hot water heating during solar peak hours

This is the single most effective step and costs nothing to implement. Most heat pump controllers allow you to set specific times for hot water heating. Move your hot water cycle from overnight to mid-morning or early afternoon (10am-2pm) when solar generation peaks.

A typical hot water cycle uses 2-4 kWh of electricity. If your panels are generating 2-3 kW during this period, the entire hot water cycle runs on free solar electricity. Over a year, this alone can save £150-250 compared to heating water with grid electricity.

2. Use a solar diverter

Devices like the myenergi eddi monitor your solar generation and grid import in real time. When surplus solar is available, the eddi diverts it to an immersion heater in your hot water cylinder, ensuring no surplus is wasted. Cost: approximately £400-600 installed.

The eddi works alongside your heat pump rather than replacing it. The heat pump heats water efficiently using the refrigerant cycle, while the eddi tops up the cylinder with any remaining surplus via the immersion element. Some owners use the eddi as the primary hot water source in summer, giving the heat pump a rest.

3. Install a battery storage system

A home battery (5-10 kWh) stores surplus solar electricity for use later in the day when the sun has set but you still need heating or hot water. This is particularly valuable for running the heat pump during evening hours. Batteries increase solar self-consumption from a typical 30-40% to 60-75%.

Cost: £3,000-5,000 for the battery, but the payback period is improving as battery prices fall. See our combined system guide for a full cost analysis.

4. Pre-heat your home during solar hours

On sunny spring and autumn days, set your heat pump to run a heating cycle during peak solar hours even if your thermostat is not calling for heat. Raising the house temperature by 1-2°C during the day using free solar electricity means the heat pump does less work in the evening when you would be buying grid electricity.

This is essentially using your home's thermal mass as a battery. A well-insulated home can hold this extra warmth for hours, providing free heating long after the sun has set.

5. Smart tariff integration

If you are on a time-of-use tariff like Octopus Agile, you can combine solar self-consumption with tariff optimisation. Use solar during the day, cheap grid electricity overnight, and only buy at full rate during the short gap between solar and off-peak periods. This comprehensive approach can reduce effective electricity costs to 8-12p per kWh on average.

How Much Can You Actually Save?

Let us model a realistic scenario for a UK home with a 4 kWp solar array and an air source heat pump.

Without solar diversion strategy

Annual solar generation: 3,800 kWh. Self-consumption (baseline household use): 35% = 1,330 kWh. Exported: 2,470 kWh. Export income at 5p/kWh: £123.50. Grid electricity saved: 1,330 kWh x 24p = £319.20. Total annual benefit: £442.70.

With solar diversion to heat pump

Annual solar generation: 3,800 kWh. Self-consumption (with HP scheduling + diverter): 65% = 2,470 kWh. Exported: 1,330 kWh. Export income at 5p/kWh: £66.50. Grid electricity saved: 2,470 kWh x 24p = £592.80. Total annual benefit: £659.30.

The difference

By prioritising self-consumption over exporting, you gain an extra £216.60 per year. Over 25 years (the life of solar panels), that is over £5,000 in additional savings. And this is without accounting for electricity price rises, which would increase the value of self-consumed electricity further.

Add a battery and the self-consumption rises to 70-80%, with proportionally greater savings. The battery adds upfront cost but typically pays for itself within 8-12 years through increased self-consumption.

The Export Tariff Still Has a Role

This article is not suggesting you should never export. There are times when exporting makes sense:

Peak summer days: Your panels may generate 25+ kWh while your total demand (including heat pump hot water) is only 8-10 kWh. The surplus has to go somewhere
Agile export spikes: On Octopus Agile Outgoing, export rates occasionally spike to 15-25p/kWh during high-demand periods. Exporting during these windows can be more valuable than self-consumption
Battery full: Once your battery and hot water cylinder are fully charged, exporting the remainder is the only option (other than curtailment)

The smart approach is hierarchical: first use solar to power your current electrical load, then divert surplus to the heat pump for hot water or pre-heating, then charge the battery, and only then export what remains. This maximises the value extracted from every kWh your panels generate.

Equipment You Need for Solar-Heat Pump Integration

Essential

Smart meter: Required for export payments and enables TOU tariffs
Heat pump with flexible scheduling: Ability to set hot water and heating times
Solar PV monitoring: To track generation and self-consumption

Optional

Battery storage: £3,000-5,000 — significant but not essential
EV charger with solar integration: If you have an electric vehicle, this provides another sink for surplus solar

For comprehensive information on solar PV systems, panels, and installation, our sister site Home Solar Guide covers everything in detail.

Common Mistakes to Avoid

Exporting everything by default

Many homeowners install solar panels and simply accept the export tariff without optimising self-consumption. This is leaving money on the table. Even basic scheduling changes (moving hot water heating to midday) can save £100+ per year.

Oversizing the export tariff's importance

Some people choose their solar panel size based on how much they can export. This is backwards. Size your system for maximum self-consumption first. Export income is a bonus, not the goal.

Ignoring seasonal patterns

Your diversion strategy should change with the seasons. In summer, you have abundant solar surplus for hot water and pre-heating. In winter, solar contribution is minimal and your tariff strategy matters more. Adjust your heat pump schedule seasonally for best results.

Frequently Asked Questions

How much is the export tariff for solar panels in 2026?

Export tariff rates in 2026 range from 3p to 15p per kWh depending on your supplier and the type of tariff. Fixed export rates are typically 4-7.5p/kWh. Variable export tariffs (like Octopus Agile Outgoing) average 5-10p but can spike higher during peak demand. You need a smart meter to receive export payments.

Is it better to export solar electricity or use it for my heat pump?

Almost always better to use it. Self-consumption saves you the full import rate (approximately 24p/kWh) while exporting earns you only 4-7p/kWh. When you factor in the heat pump's COP multiplier, each kWh used for heating is worth 3-4 times the import rate avoided. The only exception is during very high agile export rate spikes.

Can my heat pump automatically use solar surplus?

Some modern heat pumps can integrate directly with solar monitoring systems. Others need external equipment like a myenergi eddi or a home energy management system to coordinate. At minimum, you can manually schedule your heat pump's hot water cycle during peak solar hours — this costs nothing and captures most of the benefit.

What happens to my export payments if I increase self-consumption?

Your export payments will decrease because you are exporting less. However, the electricity you save by self-consuming is worth 3-6 times more than the export payment you forgo. You come out significantly ahead financially. Think of it as choosing between earning 5p or saving 24p — the maths is clear.

Do I need to tell my energy supplier I have a heat pump?

For standard tariffs, no. For specialist heat pump tariffs like Octopus Cosy, you will need to verify you have a heat pump installed. For grant purposes, your heat pump must be installed by an MCS-certified installer who will handle the relevant notifications.

Can I switch export tariff suppliers independently of my import tariff?

Yes. Your export tariff supplier does not need to be the same as your import tariff supplier. You can shop around for the best export rate independently. However, some suppliers offer package deals that combine competitive import and export rates — Octopus Energy is particularly strong in this area.