Comparisons & calculators

What will it cost to run, and which one do you actually need? Calculators that show their working.

Last updated October 2, 2026

The price on the shelf is only part of what you pay. A space heater, a dehumidifier or a second freezer keeps costing money every month it runs, and two models that look alike can draw very different amounts of power. Those are the sums this section does.

Every calculator here does one job and shows it. The formula sits next to the result. Each assumption has a stated default you can change. Any figure that comes from outside, such as an electricity price, names the agency that published it and the month it describes. When the figure is an average, the page says whose average it is and how it's worked out, because your own bill will rarely match an average exactly. The arithmetic runs in your browser, and nothing you type is sent to us.

Comparisons follow the same rules. We line products up only on figures their makers publish, converted to the same units, and we point out where two makers measure the same thing differently. We don't invent scores or star ratings.

How a calculator page is laid out

1. The answer for a typical case, in a sentence or two.
2. The calculator, for your own numbers.
3. The formula and the assumptions behind it.
4. Where the data comes from, with its release date.
5. A worked table you can read without JavaScript.

Calculators in this section

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