Export and Self-Consumption, Explained

Self-consumption is the share of solar electricity a household uses itself, at the moment it is generated or later from a battery, while export is the surplus that flows back to the grid. The distinction matters financially because a kilowatt-hour used at home typically displaces a kilowatt-hour bought at the full retail price, while a kilowatt-hour exported typically earns only an export payment, which is usually lower. A system that self-consumes a high share therefore saves more per unit generated than a system that exports most of its output, even if both generate the same total.

That simple comparison is complicated by tariffs: some export tariffs vary by time of day, some import tariffs offer cheap overnight rates, and some arrangements pay differently for different export volumes. The household pattern, not just the tariff headline, decides the result.

Raising self-consumption means matching loads to solar hours: running washing machines, dishwashers, water heating and battery charging when panels are producing, and shifting flexible loads away from evening peak times. Timers, smart appliances and surplus controls help, but they only help if the household pattern allows shifting: a home empty all day cannot self-consume much without a battery, however good its timers are.

Metering determines what is actually measured. Some systems measure export at the meter, others estimate it, and the difference affects payment and the ability to verify claims. A smart meter that records half-hourly import and export gives the household real data to check a financial case against, while an estimated arrangement leaves more room for dispute.

Before judging a financial case, list the loads that can move to daytime and those that cannot, and check the import tariff, the export tariff and any standing charges together, since a cheap export rate can be offset by a higher import rate on the same tariff. Ask for the assumed self-consumption share with and without a battery, and for the monthly pattern, not just an annual average.

Also ask whether the export tariff is fixed or variable, whether it has a cap or a minimum, and what happens if the supplier changes. A financial case built on a single export rate that can change next year should be read as illustrative, not as a promise.

In the EU, export and self-consumption arrangements are national: some member states use net metering, where exports offset imports over a billing period, others use feed-in payments, and others use market-based export prices, sometimes with taxes or grid charges on self-consumed electricity. Those differences can reverse the battery case between neighbouring countries.

In the UK, the Smart Export Guarantee requires larger suppliers to offer an export tariff, but the rate, terms and metering requirements are supplier-specific, and smaller suppliers may offer different terms. Network rules on export capacity and connection also vary by local operator, so the local arrangement should be checked rather than assumed from a national headline.

A frequent mistake is comparing solar systems by generation alone, without asking how much will be self-consumed at retail value and how much exported at a lower value. Another is assuming an export tariff will stay fixed for decades, when most tariffs can change with notice.

A third mistake is buying a battery solely to chase a low export rate, without checking whether evening demand is large enough to use the stored energy regularly. The battery should be sized to evening demand and tariff structure together, not to export frustration alone. One more tariff detail to confirm is how export is treated when the home also imports at the same half hour, since some metering arrangements net the two flows while others record them separately, and that accounting choice changes the measured self-consumption share even when the physical flows are identical.

Keep the import and export tariff terms, the self-consumption calculation with its assumptions, the metering arrangement note and the monitoring data once the system runs. Comparing actual import, export and self-consumption in the first year against the proposal is the best audit of the financial case.

Ask a qualified installer or supplier: what self-consumption share do you assume, what export rate applies and for how long is it fixed, how is export measured, and what changes the case if tariffs move. Tariff-specific answers show a realistic case.