1. Divert surplus to hot water
A solar diverter such as the iBoost or Eddi sends spare electricity from your panels to your immersion heater. This heats your hot water cylinder for free during the day. It directly replaces gas or grid electricity that you would otherwise pay for. Most households can cut their annual gas bill by £80 to £150 using this method (Energy Saving Trust, 2026). The equipment costs around £400 to £700 installed, and payback is typically three to five years. This is the fastest-returning use for surplus solar because it captures energy that would otherwise be exported for a low payment.
- Works with any standard immersion heater and hot water cylinder
- No battery or complex wiring needed; most diverters are retrofittable
- Savings depend on how much hot water your household uses during daylight
2. Charge a home battery
A home battery stores excess daytime generation for use in the evening, when your panels are not producing. This raises your self-consumption rate from roughly 30% to 70% or more. A typical 5kWh battery costs £2,500 to £4,500 installed, with payback between five and seven years. Annual savings are £120 to £200 depending on your electricity tariff and usage pattern (Energy Saving Trust, 2026). Batteries also give you resilience during power cuts if paired with an appropriate inverter.
- Most effective if you are out during the day and use power in the evening
- Check your inverter is compatible before buying a battery
- Warranty periods are typically 10 years, so choose a reputable installer via TrustMark
3. Power an electric vehicle
Plugging your electric vehicle in during sunny hours lets you charge from surplus solar rather than grid electricity. This can save up to £250 a year compared to charging on a standard variable tariff (Ofgem, 2026). You will need a smart charger that can be set to operate only when your panels are generating. Many modern chargers have solar-only modes that adjust charging rate based on real-time generation.
- Best for households with a driveway or off-street parking where the car is home during the day
- A 3.6kW solar array can add around 30 miles of range on a sunny day
- Check your vehicle’s maximum charge rate to avoid overloading your inverter
4. Run high-energy appliances during peak sun
Using timers or smart plugs to run washing machines, dishwashers, and tumble dryers when your panels are generating most can shift 15% to 25% of your household electricity use into solar surplus. This saves £40 to £80 a year on your electricity bill (Energy Saving Trust, 2026). No new equipment is needed if your appliances have delay-start functions. Smart plugs with energy monitoring let you see exactly how much solar power each appliance uses.
- Target appliances that use heating elements (dishwashers, washing machines) for biggest savings
- Use a whole-home energy monitor to identify which appliances run during your generation peak
- Set timers to start around 11am when solar output is typically highest
5. Heat a greenhouse or shed
Connecting a small electric heater or propagator to a solar relay switch gives you free heat in outbuildings during daylight hours. This is useful for extending the growing season in a greenhouse or keeping a shed frost-free. The equipment cost is low, typically under £100 for a relay and heater. No specific grant or savings figure is available, but the qualitative benefit is a longer growing season and reduced risk of frost damage.
- Use a relay that only activates when generation exceeds a set threshold
- Choose a heater with a built-in thermostat to avoid overheating
- Suitable for hobby gardeners rather than commercial growers
6. Top up an electric immersion heater manually
If you do not want to buy a dedicated solar diverter, you can fit a simple timer to your existing immersion heater. Set it to activate only during midday solar generation peaks, typically 11am to 3pm. The timer costs under £20 and can save £30 to £60 a year on gas or grid electricity (Energy Saving Trust, 2026). This is the cheapest option for using spare solar power, though it is less efficient than a diverter because it runs on a fixed schedule rather than responding to real-time surplus.
- Check your immersion heater element rating (typically 3kW) matches your solar surplus
- Use a seven-day timer to avoid heating water at weekends if you are out
- Combine with a cylinder thermostat to prevent overheating
7. Run a heat pump during the day
If you have an air-source heat pump, programming it to run during solar surplus hours can reduce its running costs by 20% to 30% (Energy Saving Trust, 2026). The heat pump stores heat in your thermal store or building fabric, which then releases it gradually through the evening. This works best with a buffer tank or a well-insulated house. No standalone grant figure exists for this use, but the savings come from replacing grid electricity with your own solar generation.
- Requires a heat pump controller that can accept external signals or timers
- Best suited to homes with underfloor heating or large radiators that hold heat longer
- Check your heat pump’s minimum run time to avoid short cycling
8. Charge portable power stations
Portable power stations such as Jackery or Bluetti can be charged from your solar surplus via a standard three-pin plug. You then use the stored power for camping, outdoor events, or emergency backup. No specific UK source provides savings figures, but the qualitative benefit is off-grid convenience and reduced use of disposable batteries. These units typically hold 0.5kWh to 2kWh, so they absorb surplus that would otherwise be exported.
- Choose a unit with a lithium battery for longer life and faster charging
- Use a smart plug to start charging only when generation exceeds a set level
- Portable stations are not eligible for the Smart Export Guarantee if you charge them instead of exporting
9. Export to the grid for payments
With a smart meter, you can earn 4p to 6p per kilowatt-hour under the Smart Export Guarantee (SEG) from most suppliers. For a typical 4kW system, this generates £60 to £120 a year in export income (GOV.UK, 2026). The SEG is paid for every unit you export, with no cap on volume. You do not need to install any extra equipment, but you must have a smart meter and an eligible tariff.
- Compare SEG rates from different suppliers; rates vary from 3p to 15p per kWh
- Export income is tax-free for most households
- You cannot claim SEG if you use a battery that stops exports
10. Power garden lighting and pumps
Connecting solar-compatible garden lights, pond pumps, or irrigation timers directly to your surplus via a dedicated circuit reduces outdoor electricity costs by £20 to £50 a year. This is a qualitative estimate; no specific UK source provides a figure. The equipment cost is low, typically under £50 for a relay and outdoor socket. The benefit is that you run these devices during the day when your panels generate most, avoiding the need for batteries or grid power.
- Use a weatherproof relay enclosure to protect the electronics
- Choose LED garden lights for lowest power consumption
- Pond pumps should be sized to run continuously during daylight hours
Spare solar power is best used to heat hot water or charge a battery, as these deliver the highest savings and fastest payback. For most households, a solar diverter is the simplest and most cost-effective first step, followed by battery storage if you want to shift energy to evening peak times.
Frequently Asked Questions
The best use is diverting surplus to hot water, saving £80-£150 per year with a payback of three to five years, according to the Energy Saving Trust (2026). It requires no battery and works with a standard immersion heater.
Yes, but indirectly. A solar diverter heats your hot water cylinder, which can supplement space heating if you have a wet system. Direct electric heating is less efficient and not recommended by the Energy Saving Trust.
You can save £120-£200 per year with a typical 5kWh battery, according to the Energy Saving Trust (2026). This raises self-consumption from around 30% to 70% or more.
A solar diverter, like iBoost or Eddi, sends spare solar electricity to your immersion heater instead of exporting it. It heats your hot water cylinder for free, directly replacing gas or grid electricity.
Yes, you need a smart charger with a solar-only mode that adjusts charging rate based on real-time generation. Many modern chargers offer this feature. This allows you to use surplus solar power efficiently.
