Water heater running cost calculator

How to use this water heater running cost calculator

Choose a mode, type in the numbers from your heater and your bill, and the calculator shows an estimated cost per year and per month. Everything it shows comes from what you enter.

Choose Mode A, "From the Energy Label (annual kWh)", if you have the Energy Label. Enter the annual energy consumption in kWh and the showers your home takes a day. Choose Mode B, "From rated power (kW)", if you only know the rated input power from the label or nameplate, and enter the minutes the heater runs a day. If you are still working out what size of heater you need, try the water heater size calculator first.

Where to find the numbers

The Energy Label from the National Environment Agency (NEA) covers water heaters and rates efficiency in ticks, from 1 (Low) to 5 (Excellent). It shows the figures both modes need.

Your tariff is the rate in cents per kWh on your electricity bill. SP Group says electricity tariffs are revised every quarter to reflect the actual cost of electricity. Because the rate moves, read it off your latest bill or check the current tariff on SP Group's page each time, rather than reusing an old figure.

How the calculation works (method and sources)

Both modes find the energy used in a year, multiply it by your tariff in cents per kWh and divide by 100 to give a yearly cost. The monthly cost is the yearly cost divided by 12.

Mode A scales the label's annual kWh from 3 showers a day, the label assumption, to the number you enter. This assumes cost grows in proportion to showers, which is a simplification. Real use depends on how long each shower runs and how hot the water is, and the result says so.

Mode B multiplies the rated power by the hours the heater runs each day and by 365. It assumes full power for the whole time you enter. Instant heaters do not run at full power all the time, so for them Mode B is an upper bound.

The method uses only the label figures NEA sets out and the tariff from your bill. The script has no stored prices or tariffs: 27 cents per kWh is just a starting value for you to replace. The result is a rough guide to your water heater electricity cost in Singapore, not your next bill.

Instant, storage and gas heaters

Mode A suits any electric heater with an annual kWh on its Energy Label, whether instant, storage or heat pump. Mode B suits any heater whose rated kW you know, but for an instant heater, read its result as an upper bound. To see how instant and storage heaters compare, see instant or storage running cost.

The calculator covers electric heaters only. On the Energy Label, NEA rates gas instantaneous water heaters on a gas cost assumption of 22 cents per kWh and 3 showers a day, and shows their nominal heat input rather than a rated input power. The calculator does not work out gas heaters. If you are choosing between fuels, see gas or electric water heater.

Limits of this estimate

The result is an estimate from your inputs, not a bill. Keep these limits in mind:

• It covers electric water heaters only.
• Storage heater standby losses are included only in Mode A, as far as the label figure includes them. Mode B does not model them.
• Tariffs change every quarter, so an old rate gives an out-of-date result.
• It covers one appliance. For the rest of your home, use the electricity cost calculator.

If your heater trips the power, leaks or is old, see the water heater replacement cost guide. Adding the electrical point for a water heater is work for a Licensed Electrical Worker (LEW): EMA says the addition of electrical power points should be carried out or supervised by an LEW. Other pipework is work for a PUB Licensed Plumber; PUB lets a handyman replace only the pipe between a stop valve and an instantaneous water heater. For the trade itself, see water heater installation and repair.

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