On a bright afternoon an 800 W balcony array produces roughly enough to run a fridge, a broadband router, a television, a laptop, and the standby draw of everything else in a two-bedroom flat, all at once, with a little left over.
On a dull January morning it produces enough to run the fridge. Both of those are true and the gap between them is the honest answer to this question.
The number that matters is your baseload
Most flats draw between 150 W and 400 W continuously, all day and all night, without anyone doing anything. Fridge-freezer, router, standby power, an always-on cylinder or towel rail. That is the baseload, and it is the reason a small array is worth more than its size suggests: every watt of it is absorbed instantly, with no storage and no thought.
An 800 W array almost never produces 800 W. Peak output happens on a clear day around solar noon with the sun square on the panel; the rest of the time it is producing a fraction of that. So for a good part of the daylight hours the array is running the baseload and nothing else has to.
It does not follow that all of it gets used. On a bright afternoon the panels comfortably outproduce a flat with nobody in it, and everything above the baseload goes to the grid for nothing. The MCS self-consumption tables put the share you actually keep at roughly half to three-quarters for a system this size — better if you are home during the day, worse if you are not.
What individual appliances draw
Rough figures for the things people ask about. These are typical draws while running, not annual consumption.
| Appliance | Typical draw | Covered by 800 W on a good day? |
|---|---|---|
| Fridge-freezer (while compressor runs) | 80–150 W | Yes, easily |
| Broadband router + hub | 10–20 W | Yes |
| Laptop | 30–65 W | Yes |
| Television, 50 inch | 70–120 W | Yes |
| Washing machine (heating the water) | 1,800–2,200 W | No — but it offsets part of it |
| Kettle | 2,800–3,000 W | No |
| Electric oven | 2,000–2,500 W | No |
| Air-source or plug-in heater | 1,500–2,000 W | No |
You are offsetting, not islanding
The kettle question comes up every time, and the framing behind it is wrong. Your array is not powering individual appliances one at a time. It is feeding the flat’s incoming supply, and your meter records the difference.
Put the kettle on at noon with 600 W coming off the balcony and you draw 2,400 W from the grid instead of 3,000 W. You did not run the kettle on solar, but you paid for a fifth less of it. Everything a balcony array does is that: a continuous small subtraction from whatever you happen to be using.
The one habit that doubles the value
Run the machines at lunchtime. A washing machine cycle at one in the afternoon is largely paid for by the balcony; the same cycle at nine in the evening is paid for entirely by your supplier.
This is the part of balcony solar that people underestimate before they buy and talk about constantly afterwards. The array is visible from the kitchen and the app tells you what it is doing, so the shift happens naturally. For a household that is home during the day it is worth more than another panel would be.
It will not keep the lights on in a power cut
Worth saying plainly, because it disappoints people who assumed otherwise. A grid-tied microinverter is required to shut down the instant it stops seeing the grid — anti-islanding protection, and it exists so that a panel on your balcony cannot electrify a cable that an engineer up the street believes is dead.
A system that runs through a power cut needs a battery and a changeover arrangement, which is a different product at a different price. If backup power is what you are actually shopping for, a balcony array is not it.
Frequently asked
- Can it run my kettle?
- Not on its own — a kettle draws about three times what the whole array makes at its best. But it does reduce what the kettle costs you, because your meter only ever sees the difference between what you are using and what the balcony is producing.
- Will it work in a power cut?
- No. The inverter is required to shut down when the grid goes away, so that it cannot back-feed a line an engineer is working on. Backup power needs a battery and a changeover switch, which is a different and considerably more expensive product.
- Do I need to change anything about how I live?
- No, and it will still be worth having. But moving the washing machine and dishwasher to the middle of the day is the single change that most increases what you get out of it, and it costs nothing.