How the export rules work
A home system sends its surplus out through the meter and onto Northern Powergrid's cables, where neighbours' homes use it. You are not paid for the units the house uses itself, GOV.UK points out, only for the ones that leave (GOV.UK). Those exported units can earn money under a set of rules overseen by the energy regulator.
Ofgem administers those rules, known formally as the Smart Export Guarantee, across Great Britain (Ofgem). Some electricity suppliers, which Ofgem calls licensees, must offer an export tariff to every eligible generator. Each one decides its own rate, contract length and other terms, and Ofgem says any rate offered must always stay above zero. Ofgem also says you are entitled to be paid on actual meter readings, even where a supplier offers other arrangements (Ofgem).
Eligibility is wide. Solar PV qualifies, along with wind, hydro, micro combined heat and power and anaerobic digestion, for installations in Great Britain up to a capacity of 5 MW. Any home roof in the district sits a very long way inside that line, so the size of your system is not the question. The paperwork is.
What you need before you can sign up
GOV.UK lists three things. First, you must show that both your installation and your installer are certified through MCS, or through a scheme accepted as equivalent, such as Flexi-Orb. You can check an installer on the MCS search before you sign. Second, you need a meter that can provide half-hourly export readings, which would typically be a smart meter; GOV.UK suggests speaking to your energy supplier if you do not have one. Third, you cannot take an export tariff while you are receiving export payments under the older Feed-in Tariffs scheme, which matters if you bought a house that already had panels (GOV.UK).
That last point is worth a minute if you are buying in the district. If a house already has panels on the roof, the new owner inherits whatever arrangement came with them. Ask the seller for the MCS certificate, the installer's notice to the network operator and any Feed-in Tariffs paperwork before you complete, because those papers decide which export arrangement the system can use and who can claim it.
Your export supplier does not have to be the company that sells you electricity. Ofgem says you can apply to any licensee and use separate companies for export, electricity and gas if you wish, subject to the terms each one sets (Ofgem). Some tariffs come with conditions, so read them before you choose.
Plug-in kits are the exception most people ask about. The Energy Saving Trust says most suppliers require a valid MCS certificate, so you cannot normally sell what a kit exports, though some suppliers may offer a tariff without one (Energy Saving Trust). The plug-in solar guide covers kits in full.
A 3 kW roof in Idle and in Haworth
To show what leaves a roof, take two places at opposite ends of the district's range. Idle sits on high ground north of the city at 186 m and has one of the highest PVGIS figures we ran. Haworth, at 240 m on the western edge, has the lowest. A 3 kW system facing south at 35° makes about 2,823 kWh a year in Idle and 2,718 kWh in Haworth (PVGIS 5.3; our arithmetic). Both are more than Ofgem's typical domestic consumption value of 2,500 kWh a year (Ofgem).
The year is not the useful view, though, because output and use do not keep step. The table spreads Ofgem's yearly figure evenly across the months, about 208 kWh each. That is a simplification, but it shows where the surplus comes from.
| Month | Idle | Haworth | Even share of typical use |
|---|---|---|---|
| January | 99 | 81 | 208 |
| February | 147 | 132 | 208 |
| March | 249 | 234 | 208 |
| April | 321 | 321 | 208 |
| May | 354 | 354 | 208 |
| June | 339 | 339 | 208 |
| July | 345 | 345 | 208 |
| August | 321 | 315 | 208 |
| September | 258 | 252 | 208 |
| October | 177 | 165 | 208 |
| November | 117 | 105 | 208 |
| December | 93 | 72 | 208 |
Three things stand out. In 7 months of the year, March to September, the roof makes more than an even month's use in both places; from October to February it makes less. From April to July the two places produce exactly the same; the gap only opens up in the darker months. Of the 105 kWh a year between them, 78 kWh falls between October and February, by our arithmetic, so Haworth's lower figure is mostly a winter story, and winter is when a roof has least to export anyway. The hills and valleys guide explains how much of that gap is the terrain and how much the sky.
None of this tells you how much a particular household will export. That depends on when the power is used: a home that is busy during the day uses more of its own output, while one that is empty until evening sends more of it out. This guide does not put a percentage on it, because any single figure would be a guess about your household. Moving flexible jobs, such as the washing machine or the dishwasher, into the middle of a bright day uses more of the roof's output at home and leaves less to export; whether that is worth doing depends on the rates you pay and are paid, which this guide does not print.
The direction of the roof shifts the timing as well as the total. In Idle, the same 3 kW facing east makes about 2,241 kWh a year and facing west about 2,211 kWh (PVGIS; our arithmetic), both still close to a typical household's yearly use. The Energy Saving Trust notes that east-facing panels are less productive in the evening and west-facing ones in the morning (Energy Saving Trust), so a west roof keeps generating later into the afternoon, when a household that is out all day may be back home, and an east roof does more of its work in the morning.
Choosing an export tariff
Ofgem publishes a list of the suppliers that offer export tariffs, updates it each year, and advises shopping around (Ofgem). GOV.UK adds that suppliers decide the terms themselves, for example whether a tariff is fixed or variable, and that tariffs change over time, so it is worth checking now and then that you are still on a competitive one (GOV.UK).
This guide prints no export rates. They differ between suppliers, they change, and a rate copied onto a web page goes stale long before anyone reads it. When you compare, ask each supplier:
- whether the rate is fixed or variable, and for how long;
- whether the tariff is open to you if you buy your electricity elsewhere;
- how exports are measured and how often you are paid;
- whether a battery that charges from the grid changes the terms.
Batteries, heat pumps and the export figure
A battery stores part of the daytime surplus for the evening, so less leaves the house. GOV.UK says a storage device that can import and export electricity, such as a home battery or an electric vehicle, could also be used with an export tariff, and that a prospective supplier can advise (GOV.UK). If you add a battery to an existing system, ask the export supplier how it affects your tariff before it is fitted, and tell the network operator too. The battery guide looks at sizes and prices in the district.
A heat pump pulls the other way across the year: it uses most electricity in the months when the table shows the roof making least, and the summer surplus is still exported. The heat pump guide sets the two side by side.
Paperwork the supplier will ask for
Expect an export supplier to ask for the MCS certificate and details of your meter. The tariff is an agreement between the supplier and the account holder, so if you sell the house, ask the supplier how it handles a change of owner, and tell the buyer where the papers are. Keep the certificate with the installer's notice to Northern Powergrid, which the network guide explains. If you are still weighing up the whole project, start with what solar costs in the district and the help with paying, then use the installer checklist to make sure the certificate you will need is one the installer can issue.