Typical Power Use of Common Cabin and Camp Loads

You can't measure an appliance you haven't bought yet. So for a first draft, you borrow typical figures. This page gives some, with a warning: they're ranges from nameplates, and your own gear may sit well outside them.

The figures below come from a university extension guide in the United States. It lists the range of nameplate wattages for household appliances¹. A nameplate is the label with the maker's rating. Treat every number here as a first guess and measure later, as described on the page about measuring real draw.

Small loads that run for hours

A 12-watt LED lamp left on for 24 hours uses about 0.3 kWh, which is about 300 Wh². Switch it on for five hours in the evening instead and it's 12 W times 5 hours, or 60 Wh, since watt-hours scale with time³.

The wide ranges matter. A window fan could be a 55 W job or a 250 W job¹. That's a gap of about four to one on one line of your budget.

Big loads that run briefly

These are the loads that break small budgets. A portable heater at the top of its range pulls 1,500 W¹. Run it for one hour and that's 1,500 Wh, more than three times the small three-appliance budget on the energy budget page. The arithmetic is the same as the 100 W bulb: watts times hours³.

Heating water takes energy too. Bringing 1 litre of water from room temperature to boiling in an electric kettle takes about 0.1 kWh, or 100 Wh². If you boil it a few times a day, count each boil.

Short bursts versus long runs

Here are two ways to think about the same total.

A television drawing 100 watts for 10 hours uses 1 kWh, the same as a 1,000-watt heater for one hour². Which one hurts depends on what you're sizing.

The fridge needs its own thought

A fridge is plugged in all day, but the compressor cycles on and off. The extension guide lists a frost-free 16 cubic foot fridge at 725 W¹. It suggests dividing the plugged-in time by three to estimate how long it really runs at full wattage¹.

So for 24 hours plugged in, that's about 8 hours at 725 W, or about 5,800 Wh, using the guide's rule of thumb¹. That's a big household fridge, and a smaller or newer one may be well below it. It's also an estimate, not a measurement. A fridge is often the biggest line in a small budget, so measure yours with a meter over a full day.

Using these numbers

Pick a row for each thing you own. Guess hours. Total the watt-hours. That's your draft.

Then go and measure. A draft built from ranges is useful for deciding whether a plan is even close. It isn't a number to buy batteries on. When you're ready, From Your Budget to Battery and Panel Size shows what the total turns into.