Does leaving appliances on standby cost much?

Standby power consumption: how to work out the cost

Leaving appliances on standby usually costs little for each device. What matters is the total: how many devices you leave on standby, how many watts each one draws and how many hours a day it sits idle. Work it out in kWh first, then apply the tariff.

Start with the standby rating in watts. The appliance manual may list it, or you can read it from a plug-in power meter while the device is on standby. Then estimate how many hours a day the device spends idle. A set-top box you watch for 4 hours a day is idle for the other 20.

The monthly sum for one device is:

• standby watts x idle hours a day x 30 days = watt-hours a month
• watt-hours a month / 1,000 = kWh a month

For example, a 5W device that sits idle for 20 hours a day uses 5 x 20 x 30 = 3,000 watt-hours, which is 3kWh a month. Repeat the sum for each device you leave on standby and add the results together.

To turn kWh into money, multiply by the household electricity tariff. SP Group publishes the current rate on its tariff information page and revises it every quarter, so check the live figure there rather than a rate you remember from an old bill. If you would rather not do the sums by hand, you can run your figures through the electricity cost calculator.

What NEA advises

The National Environment Agency (NEA) notes in its energy saving tips that many appliances still draw power after they are switched off, and advises turning them off at the socket. It also suggests switching off connected devices such as modems, set-top boxes and game consoles when you are not using them. The habit to build is to switch off at wall sockets, not just with the remote or the power button.

Standby is also built into NEA's Energy Label. The label shows an appliance's annual energy consumption and cost under fixed assumptions. For aircons, the assumption is 8 hours of use a day plus 16 hours on standby, so standby time is already part of the figure on the label. NEA adds that actual consumption and cost may vary.

Which devices to switch off

This is practical advice rather than any agency's rule. Standby electricity from one device is small, so focus on the devices that sit idle for long stretches and are easy to switch off:

• TVs, set-top boxes and game consoles. They often spend most of the day on standby. Plugging them into one switched strip lets you turn the group off together.
• Chargers left plugged in. Unplug phone, tablet and laptop chargers once the device is charged.
• Microwaves with clocks. The clock display stays lit all day. If you do not use it, switch the microwave off at the socket, and expect to reset the clock when you turn it back on.
• Printers and speakers. Many are used only now and then, so switch them off between uses.

Keep these on:

• Fridges and freezers. They need power all the time to keep food cold.
• Anything that must stay on. For example, a home alarm or a medical device someone in the household relies on.

Power strips and safety

The Consumer Product Safety Office (CPSO) warns in its tips on electrical hazards at home that overloading wall socket outlets can cause fire hazards, and suggests installing additional ones if you need them. It also says that if an appliance has damaged or frayed cords, you should stop using it immediately and get the cords replaced. For electrical installation, maintenance and repair work, CPSO advises always engaging a Licensed Electrical Worker (LEW).

A switched power strip makes switching off easier. Plug the TV, set-top box and console into one strip and you can turn them all off with a single switch. Choose a strip that carries the SAFETY Mark (see SAFETY Mark on electrical products) and do not run more from it than it is rated for. The guide to power strip overload has more on using strips safely.

When the bill is still high

Standby rarely explains a big jump in your bill. This is practical advice, not a rule: if the bill rises sharply, look at the large users first. Check how many hours the aircon runs each day and night, and whether the water heater is left on for longer than you need it. Once those are checked, look at standby.

The guide to a high electricity bill goes through the checks in more detail, and the guide to electricity usage in HDB flats has figures you can compare your own usage against. If you suspect a fault in the wiring or in an appliance, have an LEW check it rather than opening anything yourself.

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