Air-conditioner cost calculator

Work out how much it costs to run a portable or window air-conditioning unit, from its power rating, usage and your electricity price.

AC unit power (W)Hours per day (hours)Days per weekElectricity price (£/kWh)

Result

Cost per year

Cost per week

How to use this calculator

Assumes the unit runs at full rated power the whole time it's on — a thermostatically controlled unit cycling on and off will typically cost less than this in practice.
For a seasonal appliance, enter days-per-week and the annual figure represents running at that rate year-round — scale it down yourself for a shorter cooling season.

Technical details: what the fields mean

AC unit power powerWatts: Power rating from the unit's label or manual — portable units are typically 700–1500W.
Hours per day hoursPerUse: How many hours a day it actually runs.
Days per week daysPerWeek: How many days a week you use it — often seasonal, so estimate for the months you actually run it.
Electricity price pricePerKwh: Your electricity price per kWh.

Methodology

Energy per week = power (kW) × hours per day × days per week. Cost = energy × price per kWh, projected to a year.

Worked example

1000W unit, 4 hours/day, 7 days/week, 27p/kWh

Inputs: powerWatts=1000, hoursPerUse=4, daysPerWeek=7, pricePerKwh=0.27

Result: £7.56/week, £393.12/year

Practical guidance

Running a unit only when needed (with a thermostat or timer) rather than continuously cuts real-world cost well below this estimate.
A well-insulated, shaded room needs less cooling time to reach a comfortable temperature.

Common mistakes

Treating the full-year projection as realistic for a purely seasonal appliance — scale it to the months you actually use it.
Ignoring that a thermostatic unit cycles on and off rather than running continuously at full power.

At 1000W, 4 hours a day and 27p/kWh, about £7.56 a week if run every day — enter your own figures above for an exact cost.