What will 800W of solar actually run?
The short answer
Your whole background, and one big thing at a time.
Fridge, freezer, router, standby: all of it, on any half-decent day, with power left over. Add a washing machine or a dishwasher at midday and you are using close to the lot.
800W is the ceiling, reached on a bright day around noon. Most of the time you have less. Thinking in terms of “which appliances” is more useful than thinking in units, so here is what the numbers look like in a real house.
What things draw
| Appliance | Roughly | Can 800W cover it? |
|---|---|---|
| Broadband router | 10W | Easily, all day |
| Fridge freezer (averaged) | 40W to 90W | Easily |
| Laptop and monitor | 60W to 120W | Easily |
| Television | 70W to 150W | Yes |
| Washing machine, 30 degree cycle | 200W average, peaks higher on the heat | Mostly, on a good day |
| Dishwasher, eco cycle | 300W average, peaks on the heat | Partly |
| Electric car, granny charger | 2,200W | Contributes about a third |
| Kettle | 3,000W | No, and it does not matter |
| Tumble dryer, condenser | 2,500W | No, contributes a third |
| Electric shower | 8,500W | No |
Typical figures for common UK appliances, given as ranges because models vary widely. Check the rating plate on your own appliance for its actual figure. These are illustrative, not measurements we have taken.
The kettle question
People fixate on the fact that a kit cannot boil a kettle. It cannot, and it does not matter, because a kettle runs for two minutes. What matters for your bill is the things that run for hours.
A fridge freezer drawing an average of 60W costs about £138 a year to run at the price cap. A 930W kit in Birmingham will cover it outright through the lighter half of the year, and most of it through the rest. That is the shape of the saving: quiet, continuous, and invisible.
And even when it cannot cover something, it reduces it. Your 2,500W tumble dryer becomes a 1,700W tumble dryer as far as your meter is concerned. Nothing is wasted; it just gets subtracted.
Through the year
This is the honest part that adverts skip. Output is not the same in December as in June. A one kilowatt south-facing setup in London produces roughly:
Month by month, for each kilowatt of panel
London, south-facing on a tilted frame. July makes about three and a half times what December makes.