What can 800 W actually run — and can it charge a car?

The car arithmetic

Two published figures, and nothing else required.

A compliant plug-in solar device is limited to 800 VA of apparent power supplied to the mains installation, and a maximum current of 3.5 A.

A residential chargepoint eligible under the government’s specification must have standard AC output “greater than 3.5kW and not greater than 7kW” — with fast AC defined as above 7 kW and up to 23 kW.

So the entire output of a compliant kit is under a quarter of the lowest power a qualifying home chargepoint is allowed to deliver. Even in full summer sun at maximum output, the device is not in the same category of equipment.

There is a second, more basic problem. A plug-in device feeds your household circuit; it is not a socket you plug things into. And the specification requires manufacturers to state clearly that “the use of extension cables, multi-way adaptors, RCD adaptors and travel adaptors are not permitted”, which rules out the improvised arrangements people imagine when they picture charging from a panel.

If solar-charging a car is the goal, that is a rooftop system with an appropriate array, and probably a battery. It is not this product, and any retailer implying otherwise is describing something the specification prohibits.

What 800 W does not cover on its own

The government response records this neatly, because respondents raised it while arguing for more than one device per home: they wanted to power “items such as kettles, toasters or irons which generally use more than 800 W”.

That is the shape of it. A kettle draws more than the whole device can produce. So does an iron, a toaster, most microwaves, an electric shower by a wide margin, and a washing machine or dishwasher during its heating phase.

This is not the device failing. When a 2 kW kettle runs and the kit is producing 600 W, the kit supplies 600 W of it and the grid supplies the rest — you still avoid buying that 600 W. But you cannot run the kettle from the panel, and sizing your expectations around big appliances is the wrong mental model.

Where 800 W actually lands

The useful frame is continuous draw through daylight, because that is electricity you would have bought anyway and the kit can cover in full.

Typical always-on household loads sit in the tens to low hundreds of watts: refrigeration, broadband and networking equipment, standby and clock loads, a laptop or two, lighting. A household that is occupied during the day, with a home office, has a baseload a small kit can genuinely cover for hours at a time.

A household that is empty from eight until six has that same baseload, minus the office — which is why our calculator makes self-consumption an input you set rather than a number we choose. With no export payment available, generation nobody is home to use is lost.

The daily figure, honestly stated

An 800 W kit angled south in London generates about 735 kWh a year on our figures, which averages a little over 2 kWh a day.

That average is close to useless as a daily expectation, and we would rather say so than let it mislead. UK generation is heavily concentrated in summer: the same kit produces multiples of that on a clear June day and a small fraction of it in December. If your interest is winter electricity, this is the wrong technology, and that is true of rooftop solar too.

Across our 25 reference locations the annual range for the same 800 W at 35° south is 554 to 834 kWh — Lerwick to Brighton. Mount it vertically on a railing and London drops to about 539 kWh.

What this framework will not let you do

Worth stating plainly, because each of these is a question people ask:

• No battery. Battery-integrated products are outside the specification, and a compliant device must carry a prominent warning that it is not to be connected to, operated with, or used in conjunction with a battery energy storage system.
• No extension leads or adaptors, as above. Wall socket, manufacturer’s lead, nothing between.
• No powering things during a power cut. A compliant inverter must “automatically disconnect from the mains supply within 100 ms” on loss of grid supply. Anti-islanding is a safety requirement, and it means the device is not backup power.
• No stacking kits until the numbers work — one device per household for now, pending the G98 amendment. See the 800 W limit.

What we could not confirm

Actual appliance power ratings. We have deliberately not published a table of “what draws what”. Real appliances vary widely by model and we have no maintained source for them; the figures on this page are the specification’s own cap, the government’s chargepoint thresholds, and our own generation dataset. If you want to know what your fridge draws, a plug-in energy monitor will tell you in an hour and we cannot.

Whether any kit is marketed for EV charging. If you see one sold that way, we would like to know — tell us — because on our reading of the specification that claim could not be met by a compliant device.