Appliance electricity cost calculator

How to use this electricity cost calculator

Enter four figures for one appliance to see what it costs to run at your tariff.

The four inputs are:

• Power in watts. The rated power from the appliance's rating plate, manual or Energy Label.
• Hours used per day. How long it runs on a day you use it. 30 minutes is 0.5 hours.
• Days used per month. Enter 30 for daily use, or fewer for something you use on some days only.
• Your tariff in cents per kWh. The rate you pay for each kilowatt-hour, from SP Group or your latest bill.

Results show per day of use, per month and per year. The calculator runs in your browser, and nothing you enter is stored or sent.

Finding the wattage

The rating plate on the appliance or its user manual gives its power in watts (W). If the figure is in kilowatts (kW), multiply it by 1,000, since 1 kW is 1,000 watts.

For water heaters, the NEA Energy Label shows the heater type and, for electric models, the rated input power in kW. Gas models show a nominal heat input instead, and this calculator covers electricity only.

The label also shows an annual energy consumption in kWh, which you can use directly instead of watts: multiply it by your tariff for a yearly estimate. NEA works that figure out under fixed assumptions, such as 3 showers a day for water heaters, so your own use can give a different result.

For aircons, the Energy Label covers casement, window, split type (non-inverter), split type (inverter) and portable units; see aircon types for how they differ. On split and multi-split systems, the label is affixed to the outdoor unit.

How the calculation works

The method has two stages. First, energy: kWh = watts x hours per day x days per month / 1,000. Dividing by 1,000 turns watts into kilowatts. Second, cost: cost = kWh x tariff.

Stop after the first stage and you have a simple kWh calculator for Singapore homes, useful for comparing energy use before any tariff comes in.

The sum is 2,000 x 0.5 x 30 / 1,000 = 30 kWh a month. To turn that into a cost, multiply 30 by your tariff in cents per kWh.

The tariff field starts at 27 cents per kWh, the figure the NEA Energy Label assumes for its annual energy cost on aircons and electric water heaters. It is NEA's label assumption, not the current tariff. SP Group revises the household tariff every quarter, so enter the figure from SP Group or your bill.

Reading the result

The calculator gives three figures:

• Per day of use. The cost of one day on which the appliance runs for the hours you entered.
• Per month. The daily figure times the days per month you entered, so 10 days of use shows 10 days, not 30.
• Per year. The monthly figure times 12.

To compare two appliances, run the calculator for each with the same hours and days, then compare the yearly figures.

To see what using one appliance less is worth, change only the hours. Halving the hours halves the energy and the estimated cost.

Ways to cut the cost

These steps come from NEA's energy saving tips for households:

• Switch off at the socket. Many appliances still draw power after being switched off, so turn them off at the socket. Switch off modems, game consoles and other connected devices when not in use.
• Switch off the water heater. Turn it off when you do not need hot water. A storage heater keeps using energy while it is on, and switching it on 10 to 30 minutes before showering is enough.
• Set the aircon at 25 degrees C. The lower the setting, the more energy the aircon uses.

NEA's Resource Efficiency Guide for New Home Owners explains that instantaneous water heaters only use energy to heat water when it flows through the unit, while storage heaters keep using energy while they are left switched on. It recommends an instantaneous heater over a storage heater as more energy efficient.

For a side-by-side look at the two types, see instant vs storage heater running cost.

If you are replacing a heater, see water heater services.

Limits of this estimate

The method assumes the appliance draws its full rated power for every hour you enter. Treat the result as an estimate, not a bill:

• Appliances cycle. Many appliances do not draw full rated power all the time. Aircon compressors and fridges cycle, so the estimate can be higher than their actual use.
• Standby is left out. Standby use is not included unless you enter it.
• Tariffs change. The tariff is revised every quarter.
• GST and rebates are not modelled.

If you are choosing a new aircon, see inverter vs non-inverter aircon. For wiring or new sockets, compare electricians in Singapore.

Questions