Tool · Sizing

How much energy you need

Choose what you need to power.

What you plug in

  • The compressor cycles on and off: over a day it uses far less than its rating plate. The power while running appears on no European label, so we do not state it.
    Size Medium · 1.1 kWh a day
    Duration Normal use · 24 hours

    Energy: measurement across 250 homes, Household Electricity Survey.

  • A full freezer holds its cold for hours even switched off: before wiring it to a battery, it is often better simply not to open it.
    Size Medium · 750 Wh a day · 47.5 W
    Duration Normal use · 24 hours

    Energy: measurement across 250 homes, Household Electricity Survey. Power: measured trace of a chest freezer, read off the chart. Draws power 66% of the time: that is a day's energy divided by the power times twenty-four hours.

  • Size Medium · 400 Wh a day
    Duration Normal use · 24 hours

    Energy: measurement across 250 homes, Household Electricity Survey.

  • The energy for one boil is small; the power it draws while boiling is large, and that is what stops half the power stations. Filling it only as much as needed is worth 39 kWh a year.
    Size 170 Wh each time
    Duration Normal use · 3 times

    Energy: DECC/Defra measurement, full kettle.

  • The European regulation sets a ceiling — under 195 Wh per kilogram of load — but a legal ceiling is not a typical consumption: it says a compliant hob stays below it, not how much yours uses.
    Size energy not known
    Duration Normal use · 1 hours
  • In Europe the microwave has no energy label: the regulation covering hobs explicitly excludes it. This is not a gap on our side, it is a gap in the rules — so there is no number here, and we will use the one on your own rating plate.
    Size energy not known
    Duration Normal use · 0.5 hours
  • If it is a filter machine left on the hot plate, the maths changes completely: up to 100 W for more than ten hours a day is a thousand watt-hours, more than everything else in the day put together. The answer here is not a bigger battery: it is switching it off.
    Size Medium · 315 Wh a day
    Duration Normal use · 12 hours

    Energy: Swiss energy label, measurement standard EN 60661.

  • Small but running around the clock: one of the few loads with a public European measurement, broken down by component.
    Size Medium · 190 Wh a day · 7.9 W
    Duration Normal use · 24 hours

    Energy: Joint Research Centre code of conduct, measured at 230 V. Power: Joint Research Centre code of conduct, measured at 230 V. Draws power 100% of the time: that is a day's energy divided by the power times twenty-four hours.

  • The range is wide because it depends on screen size, and it comes from the 2011 stock: a recent television sits much lower. On for five or six hours a day on average.
    Size Medium · 135 W
    Duration Normal use · 5 hours

    Power: measurement across 250 homes, 2011 stock, read off the chart.

  • The one convenient case: the label gives kWh per thousand hours, and that same figure times a thousand is the wattage. A single number that yields two.
    Size energy not known
    Duration Normal use · 5 hours

    Energy: European label for light sources.

  • The only air conditioner for which the European label gives hourly energy directly — exactly the number a battery needs. We have not yet collected market values: we know where the figure lives, not what range it covers.
    Size energy not known
    Duration Normal use · 8 hours

    Energy: European label for single-duct air conditioners.

  • We have no public European source. The figures in circulation come from power station manufacturers' blogs, which are not technical sources: we prefer to leave it empty and ask for your own power supply, where the wattage is printed.
    Size energy not known
    Duration Normal use · 6 hours

The three sizes are the two ends and the middle of the range measured by the source; the three durations are our starting assumptions, written under each slider.

Going further

If you want to go further, with more realistic data — simulating a fridge's compressor cycle and its thermal behaviour — turn to HTW Berlin, the only independent institute of its kind in Europe. Their calculators are in German and ask for more data than this one, but return a more accurate figure. For appliances that switch themselves on and off, here we use the energy measured over a day, which is the right number for the question “how long will it last”.