Methodology

Where the wattages come from

Power draw comes from labelling programmes and manufacturer specifications, cited per device with the date we checked. It is published as a range rather than a single figure because a category is not a device: a 32-inch LED television and a 75-inch OLED differ by several times, and one number for a television would not be a simplification but an untruth.

Where a manufacturer or labelling programme publishes an annual consumption figure, we show it separately from our own arithmetic and never in place of it. That figure is a measurement under a standard test procedure; ours is a calculation from watts and hours. Presenting one as the other would dress an estimate up as a measurement.

Where the electricity price comes from

The default tariff is the US residential average from the EIA Electric Power Monthly, quoted with the month it reports and the date the publication was released. It changes every month, which is exactly why a cost figure without a tariff and a date attached cannot be checked.

It is a national average, so it is wrong for you specifically: rates range from around 12 cents in Idaho to over 50 in Hawaii. That is why every page takes your own tariff as an input rather than pretending an average is your bill.

Why we never publish one number for a day

How much a television costs per day has at least two answers. Twenty-four hours on is one figure; four hours of evening viewing is another, six times smaller. Most pages answering this question print a single number and never say which they used, which is why no two of them agree.

So each page answers the questions separately: one hour, a full twenty-four, a day of typical use at a stated number of hours, and standby. The hours are always on the page, and you can change them.

What this does not cover

Real consumption varies with settings, brightness, room temperature, how full an appliance is and how old it is. Standard test procedures do not reproduce any particular home. These figures are good for comparing devices and sizing a decision; they are not a prediction of your bill.