Quick answer
A 3 kWp south roof in Winsford makes about 2,863 kWh a year, roughly 69% of it from April to September. In winter almost all of it is used at home; in summer much is exported unless use moves into daylight. Larger suppliers must offer payment for exports under the SEG scheme when the installation is registered under MCS.
Two destinations for every unit
Panels make direct current, the inverter turns it into the alternating current the house uses, and the electricity then goes wherever there is demand. If the kettle, the fridge or the washing machine is drawing power, the roof supplies it first and less is bought from the grid. If nothing in the house needs it, the electricity flows out through the meter to the local network and is counted as export.
The two destinations are worth different amounts. A unit used at home is a unit the household does not buy at its import price. A unit exported earns whatever the export tariff pays, and export rates are usually lower than the price of buying electricity. That is why the share used at home, often called self-use or self-consumption, matters as much as the total a roof makes.
The Winsford year, month by month
The table uses the PVGIS model for Winsford, with 3 kWp of panels on an unshaded south-facing roof at 35°, and the same size split evenly between east and west faces (PVGIS 5.3). The full set of directions and pitches is on what panels make in Winsford.
| Month | 3 kWp south | Per day | 3 kWp east and west |
|---|---|---|---|
| Jan | 96 | 3.1 | 44 |
| Feb | 152 | 5.4 | 88 |
| Mar | 252 | 8.1 | 182 |
| Apr | 332 | 11.1 | 274 |
| May | 364 | 11.7 | 332 |
| Jun | 352 | 11.7 | 332 |
| Jul | 349 | 11.2 | 325 |
| Aug | 317 | 10.2 | 281 |
| Sep | 262 | 8.7 | 203 |
| Oct | 182 | 5.9 | 119 |
| Nov | 119 | 4.0 | 58 |
| Dec | 88 | 2.8 | 36 |
The south roof peaks in May, at about 364 kWh, and bottoms out in December, at about 88. Across April to September it makes roughly 69% of its yearly 2,863 kWh. The east–west roof makes less in total, but its summer months come close to the south roof’s, while its winter months fall further behind, because a low winter sun sits in the southern sky.
What that means in a Winsford house
Most Winsford homes are heated by gas: mains gas alone heats 81.3% of households in Over & Verdin and 80.7% in Gravel, and more than 80% in every ward (Census 2021). So a typical household’s electricity goes on appliances, lighting, cooking, electronics and perhaps an electric shower, rather than on heating. That demand is spread through the day, with peaks around breakfast and the evening meal.
In the winter months the panels make so little, a few kWh a day, that the house uses nearly all of it as it comes, and the roof simply trims what is bought. In the summer months the roof can make many times the household’s daytime demand, and much of that is exported unless something in the house is using it. Spring and autumn sit between. The share used at home over the whole year therefore depends heavily on summer habits.
A June day and a December day
Averages hide how different the days are. On the table’s figures, the 3 kWp south roof makes about 11.7 kWh on an average June day and about 2.8 kWh on an average December day. In June that output builds from early morning, peaks around the middle of the day and tails off into the evening, so there are many hours when the roof is making more than a house with nobody home can use. In December the useful window is a few hours either side of noon, and on a heavily overcast day the roof may make very little at all.
Individual days swing widely around those averages. A clear spell in May can beat a dull week in July, and a bright, frosty day in February can outperform a grey one in April. The monthly figures are averages over many years of satellite data, so any one month in any one year will be higher or lower.
Moving use into daylight
Households that want to use more of their own electricity tend to shift flexible jobs into the sunniest hours. None of these needs special equipment beyond a timer or an app:
- Washing machines, dishwashers and tumble dryers set to start late morning or early afternoon rather than overnight.
- Charging laptops, power tools, e-bikes and, where there is one, an electric car during the day.
- Hot water from an immersion heater fed by a diverter, where the home has a cylinder.
- Cooking with a slow cooker or bread maker running through the middle of the day.
The gain is greatest on bright days from April to September. On a dull winter day there is little surplus to move. An east–west roof spreads its output into the morning and late afternoon, which can suit a household that is out at midday; semi-detached homes looks at that choice.
The SEG scheme, in outline
Exports are paid through the SEG scheme, which Ofgem oversees (Ofgem’s SEG page). The main points are these:
- Who must pay. Larger electricity suppliers have to offer an export tariff with a rate above zero. Smaller suppliers may choose to.
- Which systems. Installations of up to 50 kW registered under MCS, which covers home systems, with a meter able to record exports.
- What is paid. A rate per unit actually exported, measured by the meter. Rates, terms and whether they are fixed or variable differ from tariff to tariff.
- What you need. The MCS certificate for the installation, which the firm provides at handover; check the firm’s registration on the MCS search.
The export tariff pays for electricity sent out, not towards the cost of the system. Shop around, because rates vary a great deal and the best ones change often.
When exporting a lot is fine
Not every household can move much of its use into the day, and that does not make panels pointless. A roof that exports most of its summer output still cuts what the house buys in spring and autumn, still supplies the daytime base load of the fridge and standby appliances, and still earns the export rate on the rest. What it does suggest is care over sizing. A system sized to fill the roof makes sense if the household expects its daytime use to grow, for example with an electric car or a heat pump later; one sized well beyond present and likely demand mostly adds export at the lower rate.
Who holds the tariff in rented homes and flats
In a house the owner lives in, the export tariff is simply theirs. In a rented house, the tenant usually holds the electricity account, and the landlord who paid for the panels may want a say over the export side, so it should be agreed in writing; private renters and landlords covers that agreement. Where a housing association fits panels, ask who will receive export payments. In a block of flats the export usually belongs to the communal supply and the building owner, as flats and solar explains.
Where a battery comes in
A battery stores daytime surplus for the evening, raising the share used at home. It works best when there is regular surplus to store, which in Winsford means roughly March to October. In midwinter there is rarely enough spare to fill it. Batteries deals with sizing, placement and the grid rules for storage.
Reading a quote’s self-use figure
A quote from a registered firm should include an estimate of yearly output and may include an estimate of how much of it the household will use. Ask how the self-use figure was worked out, whether it assumes someone is at home in the day, and whether it includes a battery. A self-use figure that looks generous for an empty house should be questioned. For how firms present their figures, see choosing an installer, and for your own roof, try the who-decides tool.