Generating more than you use is normal on a sunny afternoon. Being paid for the surplus is a separate arrangement, and it has three parts: a meter that can measure export, an agreement with a supplier, and a declaration to the network operator.
The meter
Export has to be measured before it can be paid for. A smart meter operating in smart mode records import and export separately; an older meter generally does not, and some very old meters will happily run backwards, which is not the same thing as exporting and is not something to rely on.
If your meter cannot record export, that is the first job, and it belongs to your supplier rather than to us.
The agreement
Export payments come from an electricity supplier, not from the network operator and not from the government. Suppliers set their own rates and their own terms, and you are not obliged to sell to the same company you buy from.
Rates move often enough that any figure printed on a website is out of date by the time you read it, so we do not print one. Ask two or three suppliers directly, and read what the rate is tied to — a flat pence-per-unit and a rate that tracks a wholesale index behave very differently over a year.
The declaration
Generation and storage that can push power back onto the network has to be declared to the network operator that owns the cable in the street. Below a certain size that is a notification made after the work; above it, it is an application that must be agreed before the system is energised.
Which side of the line you fall on depends on the inverter rating and the number of phases, and we work it out and submit the paperwork as part of the installation. It is not something a homeowner should have to chase.
Why the export rate is the smaller number
The instinct is to shop for the highest export rate. Usually the bigger lever is the other one.
A unit you generate and use yourself avoids the import price. A unit you export earns the export price, which is normally a fraction of it. So the money in a storage system is mostly in the difference — every kWh moved from an afternoon surplus into an evening draw is worth import minus export, not export.
That is also why battery sizing works from the evening block rather than from generation. There is a full worked method in the field note on sizing a home battery.
In short
- No export meter, no payment. That comes first.
- The supplier sets the rate, and you can switch it independently of your import tariff.
- The declaration to the network operator is our job, not yours.
- Self-consumption is worth more per unit than export, in nearly every tariff on the market.