Does Solar Work With the Smart Export Guarantee? How UK Homeowners Get Paid for Surplus Power
This guide explains how the Smart Export Guarantee pays you for unused solar electricity, why rates differ between suppliers, and what to check before you commit.
In short
- Use an MCS-certified installer. SEG registration requires it by law.
- On our calculation, a 4 kWp system without a battery is worth around £523–£603 a year on a south-facing roof and £435–£495 east-facing if you buy your electricity from the supplier paying 12p per kWh for exports, or £299–£333 south-facing at an open rate of about 4p. These figures cover bill savings plus SEG export payments.
- VAT on home solar is 0% until 31 March 2027. A typical system costs £5,000–£10,000 to install.
- On our calculation, payback takes about 11–16 years on a south-facing roof with a 12p export rate from your own supplier, or about 20–28 years at an open rate of about 4p. Shading or a poor angle stretches that timeline.
What is the Smart Export Guarantee and who qualifies?
The Smart Export Guarantee (SEG) is a scheme that requires electricity suppliers with at least 150,000 domestic customers to offer a tariff for surplus power you export to the grid. The rate is supplier-set and must always be above zero, but it varies widely between providers, so comparing tariffs before you sign with an installer can make a meaningful difference to your returns.
To qualify, your installation must be certified under MCS (Microgeneration Certification Scheme) or an equivalent scheme. MCS certification is the standard for domestic solar in the UK, and without it you cannot register for SEG payments. This makes choosing an MCS-certified installer a practical requirement, not just a quality mark.
SEG is not a grant. It is an ongoing export payment for the electricity your panels generate beyond what you use at home. Grants and funding are separate; the Ofgem website explains the SEG rules in full for anyone who wants the official framework.
How roof, orientation and consumption shape your returns
A south-facing roof with little shading gives the best conditions for solar generation. On our calculation, a 4 kWp system without a battery is worth around £523 to £603 a year on a south-facing roof and £435 to £495 east-facing, if you also buy your electricity from the supplier that pays 12p per kWh for exports; at an open export rate of about 4p, a south-facing roof is worth around £299 to £333. That assumes a household using 2,500 kWh a year; shading lowers the result further.
How much of your generation you consume directly matters as much as the export rate. Electricity you use yourself offsets a unit you would otherwise buy, which is worth more per unit than the export payment you receive for selling it back. Running dishwashers, washing machines or EV chargers during daylight hours raises self-consumption and improves the overall return.
Roof age and pitch also play a role. If your roof needs re-tiling within a few years, doing that before panels go on avoids the cost of removing and refitting the array later. An installer will assess pitch, shading and structural condition during a site survey.
VAT, permits and the cost of going solar
Residential solar installation is zero-rated for VAT at 0% to 31 March 2027, which reduces the upfront cost compared with many other home improvements. A typical domestic system costs £5,000 to £10,000 installed, though the final figure depends on system size, roof complexity and the equipment specified.
Most domestic roof-mounted solar qualifies as permitted development, meaning no planning application is needed. Exceptions include listed buildings, properties in conservation areas, and any frame or ground-mounted system, all of which may require a planning application under the General Permitted Development Order. Local authority rules on aesthetics can also apply, so it is worth checking with your council if you are unsure.
On our calculation, payback runs about 11 to 16 years on a south-facing roof if you also buy your electricity from the supplier that pays 12p per kWh for exports, about 20 to 28 years at an open export rate of about 4p, and longer if the roof is east-facing or shaded. Knowing that range helps you weigh the investment against the life of the system: the Energy Saving Trust says panels should last 25 years or more, while inverters have shorter warranties, so at a 12p export rate a well-sited system should outlast its payback period.
Should you add a battery, and how do you compare installers?
A battery stores surplus generation for use in the evening rather than exporting it. This raises self-consumption and reduces reliance on the grid during peak-rate hours, which can improve the overall financial case. The trade-off is extra upfront cost and a shorter warranty horizon for the battery unit itself compared with the panels.
A battery is most useful when your household uses significant electricity after dark and when export tariffs are lower than the import rate you would otherwise pay. If you are rarely home during the day, a battery is likely to pay back faster than if you already use most generation directly. Ask any installer to model both options with your actual consumption profile.
When comparing quotes, look beyond the headline price. Check the MCS certificate number of the installer, the panel degradation warranty, the inverter replacement horizon, and which SEG tariff the installer recommends registering with. Getting quotes from several installers lets you weigh equipment, workmanship guarantees and post-installation support side by side, not just the total price.
How long before a typical solar system pays for itself
Illustrative cumulative position of a 4 kWp south-facing system in London at a 12p export rate (£)
| Year 1 | -6,931 £ |
|---|---|
| Year 3 | -5,753 £ |
| Year 5 | -4,575 £ |
| Year 7 | -3,397 £ |
| Year 9 | -2,219 £ |
| Year 11 | -1,041 £ |
| Year 13 | 137 £ |
| Year 15 | 1,315 £ |
Illustrative example: a 4 kWp south-facing system in London costing £7,520, the mid-point of DESNZ average installed costs for retrofitted home systems (£6,606 to £8,435 at 4 kWp), and worth £589 a year on our calculation if you also buy your electricity from the supplier that pays 12p per kWh for exports. It pays back in about 13 years. At an open export rate of about 4p the same roof is worth around £325 a year and payback takes about 23 years. Your figures depend on your roof, tariff and usage.
Illustrative example, our calculation (How we calculate)
Before you commit: what to verify
- Confirm your installer holds a current MCS certificate, as this is required to register for SEG payments.
- Check whether your property is listed or in a conservation area, which may require a planning application before installation.
- Ask each installer to quote with your actual consumption profile so self-consumption and export assumptions are based on your home.
- Compare SEG export tariffs from at least two or three suppliers before choosing which to register with.
- Review the panel product warranty length and the inverter replacement horizon in every quote you receive.
- Verify that the VAT rate applied on your quote reflects the current 0% zero-rated treatment for residential solar.
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Key terms for grants and funding UK paperwork
- Smart Export Guarantee (SEG)
- A scheme that requires large electricity suppliers to pay homeowners for surplus solar power sent to the grid. Each supplier sets its own rate, but the rate must be above zero. SEG is an export payment, not a grant.
- MCS (Microgeneration Certification Scheme)
- The UK standard for home solar installs. MCS certification is required before you can register for SEG payments. An installer without MCS certification cannot sign you up for the scheme.
- Self-consumption
- The share of solar power you use directly in your home rather than sending to the grid. Using power as you make it typically saves more per unit than the export rate you receive under SEG.
- Zero-rated VAT
- A VAT treatment that applies a 0% rate to the install, so no VAT is added to the bill. This rate currently applies to home solar installs until 31 March 2027.
Frequently asked questions
Answers to the most common questions.
Is the Smart Export Guarantee the same as a government grant for solar?
No. SEG is an export payment for surplus electricity you send to the grid; it is not a grant. Grants for solar, such as those under ECO4 or the Warm Homes Plan, are means-tested or property-based schemes with separate eligibility rules. SEG payments continue for as long as you generate and export power.
What export rate will I get under the Smart Export Guarantee?
Rates are set by each supplier and must be above zero, but there is no fixed floor beyond that. Rates vary widely, so it pays to compare current SEG tariffs from multiple suppliers before registering. Your installer can advise on which suppliers are offering competitive rates at the time of your installation.
Do I need planning permission to install solar panels?
Most domestic roof-mounted solar qualifies as permitted development, so no planning application is required. Listed buildings, conservation areas and ground-mounted systems are exceptions and may need permission under the General Permitted Development Order. Check with your local planning authority if your property falls into one of these categories.
How do I find out what solar grants or funding I am entitled to?
Eligibility depends on household income, property type and energy efficiency rating. ECO4 and the Warm Homes Plan are the main current routes for low-income households. Getting quotes from several MCS-certified installers is a practical first step; they can confirm which schemes apply to your home and help you apply.