Power for cooking: batteries, inverters and solar

Cooking is the heaviest electrical load most people ever ask a portable battery to carry. A phone is a rounding error. A laptop is trivial. An induction hob is in a different category entirely, and the reason people get this wrong is that there are two numbers involved and the shops advertise the less important one.

Watts and watt-hours are not the same question

Watts (W) are a rate. They decide whether the thing will run at all.

Watt-hours (Wh) are a quantity. They decide how long it will run for.

A battery has to satisfy both independently. A large battery with a small inverter will refuse to start a 2,000 W hob no matter how full it is, and waiting does not help. A powerful inverter on a small battery will start the hob and then flatten itself.

So there are two checks, in this order:

1. Is the power station’s continuous output rating at least the appliance’s rating? If not, stop. Nothing else matters.
2. Is its capacity comfortably more than the job costs in watt-hours?

The arithmetic

Watt-hours are watts multiplied by hours. That is the whole formula.

A 2,000 W hob run for twenty minutes is 2,000 × (20 ÷ 60), which is about 670 Wh. Some worked examples, using the ratings these appliances are sold at:

Three things fall out of that table, and they are the useful conclusions on this page.

The microwave is the cheapest electric meal by a wide margin. It draws a lot, briefly. Judged on watt-hours rather than watts, it is the most battery-friendly electric option there is, which is the opposite of most people’s intuition.

Induction is affordable once you stop boiling. Getting to temperature is where the energy goes. Holding a simmer costs a fraction of the rating, and almost everything on this site is a short boil followed by a long simmer.

The electric grill is the expensive one, because it draws near its full rating for the whole cook rather than cycling down.

Then add the losses

Those figures are what the appliance uses, not what leaves the battery.

Inverter losses. Turning battery DC into mains AC is not free. Add a margin rather than planning to the exact number.

Do not plan to use the last of it. Running a battery to empty repeatedly is hard on it, and a power station that cuts out mid-cook has cost you the meal as well as the charge.

A practical habit: work out the watt-hours, add a third, and check that against capacity. If a 1,000 Wh unit is being asked for 750 Wh of grilling, it is not really a one-meal-a-day battery, whatever the box says.

Pure sine wave, and the surge

Two specifications that are easy to miss and expensive to get wrong.

Waveform. Cheap inverters produce a modified sine wave, which is a coarse approximation of mains. Induction hobs and microwaves are sensitive to it in a way a phone charger is not, and the failure mode is often not a clean refusal but running hot, running strangely, or working until it does not. For cooking, buy pure sine wave.

Surge. Appliances draw more at the instant they start than they do running. Power stations quote a surge rating alongside the continuous one for this reason. A unit whose continuous rating only just covers your hob can still trip at switch-on.

What the mains can do, for comparison

A UK socket is a useful yardstick. BS 1363 plugs are rated at 13 A, which at 230 V is a ceiling of roughly 3 kW for anything you plug in.

That is why a 2,000 W hob is unremarkable in a kitchen and a serious proposition off grid: it is comfortably inside what a wall socket supplies and comfortably outside what a small power station does. When a hook-up is available, all of this stops being a problem, which is worth remembering before buying a battery for a use case that mostly happens on serviced pitches.

Solar, honestly

Solar refills the battery. It does not power the hob.

Panel ratings are measured under standard test conditions: full perpendicular sun, a specified spectrum, a cool cell. A panel flat on a roof in Britain in October meets none of those, and the realistic daily yield is a fraction of the badge figure, considerably less in winter.

Set that against the table above. If one grilled meal is 750 Wh, a modest panel at this latitude may not replace it inside a day. Solar extends a battery. It seldom replaces one.

Angle and shade matter more than size. A panel you can tilt toward the sun and move during the day will beat a larger one lying flat, and partial shading costs disproportionately more output than its area suggests.

The honest summary

For most people cooking the food on this site, a gas burner remains the right default: it is light, cheap, and independent of all of the above.

Electric earns its place in two specific cases. One is cooking in an enclosed space, where it is the only option that does not produce carbon monoxide. The other is a van or a house with a battery already sized for other things, where a microwave and a considered induction hob are a genuine upgrade in what you can cook rather than a novelty.

Buying a battery in order to cook electrically is the expensive path, and it is worth being clear with yourself about which of these you are doing.