What Happens to Excess Electricity From Plug-In Solar?

If your plug-in solar panels are producing more electricity than your home is using, what happens to the extra power?

In a typical grid-connected system, electricity generated by the solar panels is used by your home first. If generation exceeds the electricity being consumed at that moment, surplus power can flow back through the household electrical installation and into the local electricity network.

That does not automatically mean you will be paid for it.

Whether you can receive export payments depends on metering, eligibility, certification and the requirements of the electricity supplier offering the export tariff.

This guide explains the difference between generating, using and exporting electricity from plug-in solar in Great Britain.

Your home uses solar electricity first

A plug-in solar device operates in parallel with the household electricity supply.

When the panels are generating electricity, that power contributes to whatever electrical demand exists in the home at that moment.

For example, your home might be using electricity for:

• a fridge
• broadband equipment
• lighting
• a computer
• television
• standby appliances

If the solar system is producing 400W while the home is using 500W, the solar generation can offset part of that demand.

The remaining electricity would still come from the grid.

The exact behaviour depends on the system, household loads and installation, but the principle is simple: electricity generated and consumed at the same time can reduce the amount you need to import.

That is known as self-consumption.

What happens when solar generation exceeds household demand?

Suppose the solar system is producing 600W, but the home is currently using only 250W.

There is approximately 350W more generation than immediate household demand.

In a normal grid-connected arrangement, surplus electricity can flow back toward the electricity distribution network unless the particular equipment or installation is configured to limit export.

The official Plug-in Solar Device Interim Product Specification covers systems designed to operate in parallel with the low-voltage electricity network and allows the household electrical installation to be used for plug-in solar generation export.

That is different from an off-grid solar system, where there is no connection to the public electricity network.

Does exporting electricity reduce your electricity bill?

Not directly in the same way as self-consumption.

The easiest electricity saving to understand comes from avoiding grid imports.

If your home would normally buy 1 kWh from the grid but instead uses 1 kWh generated by your solar panels, you avoid buying that unit of electricity.

Exported electricity is different.

Once electricity leaves the property, you only receive financial value from it if you have an appropriate export-payment arrangement.

Without one, surplus electricity may still be exported but you should not assume that you are being paid for it.

That is why self-consumption is particularly important for small plug-in solar systems.

You can estimate the potential value of the electricity you actually use with our plug-in solar savings calculator.

Can you get paid for exported plug-in solar electricity?

Potentially — but it is not automatic.

In Great Britain, the main regulated export-payment framework is the Smart Export Guarantee, usually called the SEG.

Under the SEG, participating electricity suppliers offer tariffs that pay eligible small-scale generators for metered renewable electricity exported to the grid.

Solar photovoltaic systems are one of the eligible generating technologies.

However, owning solar panels alone does not automatically qualify an installation for payments.

Ofgem's rules include requirements around:

• eligible generation technology
• location in Great Britain
• installation capacity
• export metering
• suitable installation certification
• applying to a SEG licensee

The export supplier can also have its own application and evidence process.

Does plug-in solar automatically qualify for the Smart Export Guarantee?

You should not assume that it does.

Plug-in solar is new to the Great Britain market, while the Smart Export Guarantee framework was designed before today's simplified plug-in solar category existed.

Ofgem's guidance says qualifying exported electricity must be metered.

For smaller solar PV installations, certification requirements also apply.

If an applicant cannot demonstrate suitable installation certification, a SEG supplier is not necessarily required to offer payments, although suppliers have some discretion.

This creates an important practical question for plug-in solar owners:

Will the SEG supplier accept the documentation for your specific plug-in installation?

The answer may vary by supplier and by the evidence available for the system.

Before buying a plug-in solar kit primarily because you expect export income, ask the prospective SEG supplier what documentation it would require.

Do not base the purchase economics on export payments unless eligibility has been confirmed.

Do you need a smart meter?

To receive SEG payments, exported electricity needs to be measured.

A smart meter may be capable of recording export electricity, but having a smart meter does not automatically mean:

• export measurement is enabled
• your supplier receives the necessary export readings
• you qualify for a SEG tariff
• you have been registered for export payments

Meter arrangements vary.

If export payments matter to you, ask the SEG supplier whether your current meter is suitable and what setup is required.

We will cover this in more detail in our dedicated smart-meter guide.

Is your electricity supplier the same as your export supplier?

Not necessarily.

Ofgem allows consumers to choose a SEG licensee independently of the company supplying their electricity.

For example, one company could supply the electricity you buy from the grid while another company pays you for eligible exports.

The available tariffs, rates and application requirements can vary between SEG suppliers.

Ofgem publishes the current list of SEG licensees (see our official resources).

How much electricity might an 800W plug-in solar system export?

There is no useful single answer.

Export depends heavily on how much electricity your household is using while the system is generating.

Two homes with identical 800W systems could have very different export levels.

A home with:

• people working from home
• daytime appliance use
• regular daytime cooking
• constant electrical loads

may consume much of its solar generation directly.

A mostly empty home with low daytime electricity demand may export a greater proportion.

Weather, panel direction, shading and season also affect generation.

This is why PlugInSun focuses on self-consumption rather than assuming that every kilowatt-hour generated has the same financial value.

Is it better to use solar electricity instead of exporting it?

Often, yes — particularly when the price you avoid paying for imported electricity is greater than the export rate available to you.

But you should compare the actual numbers.

For example, suppose avoiding one unit of imported electricity saves more than your export tariff would pay for sending that same unit to the grid.

In that situation, using the electricity yourself can be more valuable.

That does not mean you should waste electricity simply to avoid exporting it.

The aim is to shift useful, normal consumption toward periods when the panels are generating where convenient.

Practical ways to increase self-consumption

You do not need to redesign your lifestyle around a small solar installation.

Simple timing changes may help.

Where appropriate, you could run ordinary household activities during daylight hours rather than later in the evening.

Examples might include:

• dishwasher cycles
• washing machine cycles
• device charging
• other flexible household loads

Always follow appliance instructions and normal electrical-safety practices.

Do not overload circuits or add electrical equipment simply to consume solar generation.

Would a battery prevent electricity being exported?

Battery storage can potentially capture some surplus solar generation for later use.

However, this needs an important qualification for plug-in solar.

Great Britain's current simplified plug-in solar product specification does not extend to plug-in battery systems or plug-in solar devices integrated with batteries.

You should therefore not assume that a battery can simply be added to a compliant plug-in solar kit.

Read our full guide:

Can You Use a Battery With Plug-In Solar in the UK?

If you want home battery storage, treat it as a separate electrical and financial decision.

Does exporting affect DNO notification?

Export payments and network notification are separate issues.

A compliant plug-in solar device operates in parallel with the local distribution network, and the applicable network notification requirements still matter regardless of whether you receive money for exported electricity.

Your Distribution Network Operator (DNO) manages the local network.

Your electricity supplier sells you electricity.

A SEG licensee may pay you for qualifying exports.

These organisations can be different.

For the network-registration side, read:

Do You Need to Notify Your DNO About Plug-In Solar?

What about Northern Ireland?

The Smart Export Guarantee discussed in this guide applies to Great Britain.

Northern Ireland has separate electricity-market and network arrangements.

The Great Britain G98 framework also differs from G98/NI.

Consumers in Northern Ireland should therefore check current local guidance rather than assuming Great Britain export or registration arrangements apply.

What should you check before buying?

If export income is part of your reason for buying plug-in solar, check these points first.

1. Estimate how much solar you are likely to use yourself

Start with household daytime demand.

The more generation you consume directly, the less dependent the financial case is on export payments.

2. Check your meter

Find out whether your meter can accurately record exported electricity.

3. Ask a SEG supplier about eligibility

Tell them what type of plug-in solar installation you are considering and ask what certification or documentation they require.

4. Do not assume advertised export savings

Be cautious if a retailer includes export income in projected savings without explaining the eligibility assumptions.

5. Calculate savings without export income first

This gives you a more conservative view of the purchase.

Then treat confirmed export payments as an additional benefit.

Use our savings calculator to estimate potential self-consumption savings.

Key takeaways

• Plug-in solar electricity is used by household loads while it is being generated.
• Surplus generation can flow back to the electricity network in a normal grid-connected arrangement.
• Exporting electricity does not automatically mean you are paid for it.
• Great Britain's Smart Export Guarantee can pay eligible solar generators for metered exports.
• SEG eligibility includes metering and certification requirements.
• Do not assume a plug-in solar installation automatically qualifies for a SEG tariff.
• Check eligibility directly with the SEG supplier before relying on export income.
• Maximising useful self-consumption can improve the value of a small solar system.
• Battery storage should not simply be added to a compliant plug-in solar device under the current simplified framework.
• Northern Ireland has separate arrangements.

The bottom line

When plug-in solar generates more electricity than your home is using, the surplus can normally flow back toward the electricity grid.

But export and payment are two different things.

Being connected to the grid does not automatically create an export tariff, and plug-in solar owners should not assume they qualify for Smart Export Guarantee payments without checking metering, certification and supplier requirements.

For a conservative buying decision, calculate the value of electricity you expect to use yourself first.

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