What this checker works out
This checker multiplies standby wattage by hours per day, by the number of devices, across a year, giving annual consumption and cost.
Standby power is the classic small-but-persistent cost: individually negligible, collectively a modest but real annual figure that most households never see itemised.
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Default unit rates are the Ofgem price cap average for Great Britain, Direct Debit, 1 July to 30 September 2026, including VAT. The cap is reviewed quarterly — use the rate from your own bill where it differs.
Before you estimate
- Standby draw varies enormously — a modern television may use under 0.5 W, an older set-top box 15 W or more.
- A plug-in energy monitor measures it directly for a few pounds and is far more reliable than an assumed figure.
- Hours per day means hours in standby, not hours in use. For most devices that is the time they are not being used.
- Count devices honestly. Most homes have considerably more always-on electronics than a first list suggests.
Standby consumption is not evenly spread. Modern equipment is subject to EU-derived limits of around 0.5 W in standby, so most of the total usually comes from a handful of older or always-active devices — set-top boxes, games consoles left in rest mode, older audio equipment. Finding those two or three is worth more than switching off everything else.
How this calculator works
Watts to annual kilowatt-hours, then to money:
Annual kWh = watts × hours per day × 365 × devices ÷ 1,000
Annual cost = kWh × price in pence ÷ 100
Monthly = annual ÷ 12The calculation applies one wattage to every device, which is a simplification — real households have a spread. Running it separately for the few high-draw devices and once for everything else gives a more useful picture than a single average.
Worked example: three devices at 5 W
Using the default figures — three devices drawing 5 W for 20 hours a day, at 26.11p per kWh:
- Annual consumption: 109.5 kWh
- Annual cost: £28.59
- Monthly equivalent: £2.38
£29 a year for three devices. The useful comparison is that a single old set-top box drawing 15 W around the clock costs £34 on its own — more than the three devices above combined. That is why measuring rather than assuming matters: the total is usually dominated by one or two items that a general standby cull would not prioritise.
Common mistakes
- Assuming a standby figure. Devices differ by a factor of thirty; measure where you can.
- Unplugging everything indiscriminately. Modern devices draw almost nothing; find the few that matter.
- Switching off equipment that needs to stay on. Routers, alarms, freezers and some heating controls are not standby loads.
- Counting hours in use rather than hours in standby.
- Expecting large savings. It is a genuine but modest figure, not a transformation.
Frequently asked questions
How do I measure standby power?
A plug-in energy monitor, which costs a few pounds, plugs between the socket and the appliance and shows current draw and cumulative consumption. Leaving it on a device for a day gives a far better figure than any published estimate, and the same monitor identifies the household's genuinely expensive appliances.
Which devices are worst?
Typically older set-top boxes and digital recorders, which may stay near full power to record; games consoles in rest mode; older amplifiers and hi-fi; and anything with a permanently lit display. Devices sold in recent years are subject to standby limits and are usually well under a watt.
Should I switch things off at the wall?
For the few high-draw devices, yes, where doing so causes no inconvenience. For most modern electronics the saving is a few pence a year and not worth the disruption — and some devices need to remain powered for updates, recording or alarm functions. Target the worst offenders rather than everything.
Do phone chargers use power when nothing is plugged in?
A very small amount — modern chargers draw a fraction of a watt when idle, costing a few pence a year each. The old advice to unplug chargers dates from an era of much less efficient designs. It does no harm, but it is not where the savings are.
Is what I enter stored?
No. Figures are processed in your browser and never transmitted or retained.
Related tools
References
- GOV.UK — energy efficiency regulations, standby limits and help with bills
- MoneyHelper — practical guidance on reducing energy costs
Sources are checked at publication and can change — how I choose and check references.