Heating Cost Calculator

How the heating cost calculator works

Heating cost depends on how much energy the system consumes, how long it runs, and the price you pay for that energy. This calculator converts the entered heating power to kilowatts, estimates the required energy input, then multiplies energy use by your own price per kilowatt-hour.

Which calculation method should I use?

Power units supported

You can enter heating power in kilowatts, watts or Btu per hour. Btu/h is converted using the International Table Btu conversion, where 1 Btu/h is approximately 0.293071 W.

The conversion is based on the NIST Guide to SI conversion factors .

Worked example

Suppose a 2 kW electric heater runs for 6 hours per day and electricity costs £0.28 per kWh. The heater uses 12 kWh per day, giving an estimated daily cost of £3.36. Over 30 days, the estimated cost is £100.80.

Heating efficiency and heat-pump COP

Efficiency and COP are not the same thing. A conventional heating efficiency is normally expressed as a percentage of input energy converted to useful heat. Heat-pump COP is a ratio of heat output to energy input and can therefore be greater than 1.

Real heating costs vary with weather, thermostat settings, insulation, cycling, equipment condition and tariff structure. Use the calculator as an estimate and enter figures that reflect your actual system and energy plan where possible.

COP versus seasonal COP (SCOP)

A heat pump's coefficient of performance (COP) describes the relationship between heat output and electrical input at particular operating conditions. For example, a COP of 3 means that 3 kW of heat is delivered for each 1 kW of electrical input.

Heat-pump performance changes with operating conditions, so a single COP value does not necessarily represent performance throughout an entire heating season. Seasonal coefficient of performance (SCOP) is intended to represent efficiency across a range of conditions over a heating season.

When using this calculator for a longer-term cost estimate, use a COP or seasonal performance figure that is appropriate to the heating system and conditions being considered rather than assuming that the manufacturer's best-case COP applies continuously.

For further information, see the UK Energy Technology List guidance on heat-pump efficiency .

Running time and thermostat cycling

The running-time input represents the average number of hours per day that the heating system consumes energy at the calculated input rate. This can be different from the number of hours that the heating system is switched on.

A thermostatically controlled heater may switch on and off as room temperature changes, while variable-output systems and heat pumps can reduce or increase their power consumption according to heating demand.

For example, a 2 kW heater switched on for eight hours does not necessarily consume 16 kWh if its thermostat causes the heating element to operate for only part of that period. For more realistic cost estimates, use an average operating time that reflects actual energy consumption where this information is available.

Comparing heating costs

The purchase price of an energy source does not by itself determine the cost of useful heat. Heating-system efficiency also matters. Two systems with different energy prices can therefore have quite different running costs after efficiency or heat-pump COP is taken into account.

For a conventional heating system, the calculator divides the required heat output by the entered efficiency. For a heat pump, it divides heat output by COP. The resulting input-energy estimate is then multiplied by the energy price.

When comparing systems, use the same required heat output and operating period, then enter an appropriate efficiency or COP and energy price for each system. This provides a more meaningful comparison than comparing energy prices alone.

Frequently asked questions