The short version. One watt, left on all year, costs £2.31 at the October 2026 price cap. That single number prices everything in your house that never switches off.
UK law caps how much a device may draw when it is doing nothing. Off mode and ordinary standby are capped at 0.5W. Standby with a display is capped at 1W. Networked standby, the mode a router or a smart speaker sits in every hour of the year, is capped at 2W for most equipment and 8W for high network availability kit such as routers. A device sitting at that 8W ceiling costs £18.45 a year to do nothing.
What almost no product tells you is where on that scale it actually sits. We call that the always-on blank.
What a watt costs, left on all year
There are 8,760 hours in a year. A device drawing one watt continuously uses 8.76 kWh over those hours. At 26.32p per kWh, the Ofgem cap rate for electricity from 1 October to 31 December 2026, that is £2.31.
Everything else on this page is that sum with a different wattage in front of it. If you know what a device draws, multiply the watts by £2.31 and you have its annual cost, assuming it is never switched off.
| Continuous draw | kWh a year | Cost a year |
|---|---|---|
| 0.5W | 4.38 | £1.15 |
| 1W | 8.76 | £2.31 |
| 2W | 17.52 | £4.61 |
| 3W | 26.28 | £6.92 |
| 6W | 52.56 | £13.83 |
| 8W | 70.08 | £18.45 |
| 12W | 105.12 | £27.67 |
What the law actually caps
Standby power in the UK is governed by Commission Regulation 1275/2008, retained in UK law after EU exit with amendments applied to 31 December 2020. It sets hard ceilings, and they are lower than most people assume.
| Mode | Legal ceiling | Cost a year at that ceiling |
|---|---|---|
| Off mode | 0.50W | £1.15 |
| Standby, reactivation only | 0.50W | £1.15 |
| Standby with an information or status display | 1.00W | £2.31 |
| Networked standby, most equipment | 2.00W | £4.61 |
| Networked standby, high network availability equipment | 8.00W | £18.45 |
High network availability equipment, HiNA in the regulation, means kit that has to keep the network up: routers, network switches, wireless access points. That is why it gets the loosest ceiling. The 8W limit has applied since 1 January 2017, down from 12W when networked standby was first regulated in 2015. The 2W limit for everything else has applied since 1 January 2019, down from 6W in 2015 and 3W in 2017.
Two things follow. The first is that the worst case is bounded: a compliant device cannot quietly cost you £50 a year sitting idle. The second is that the bound is wide. Between a 0.5W off mode and an 8W networked standby there is £17.30 a year of difference, and nothing on the box tells you which end your device is at.
The always-on blank
A standby figure is only useful if somebody publishes it. Across the always-on products we have priced on this site, three different situations come up, and they are not interchangeable.
Some makers publish a maximum. TP-Link’s EU datasheets give 11.5W for a Deco X10 mesh unit and 15W for a Deco X55, both measured with the power adapter. A maximum is a ceiling, not a running cost: the real draw is lower by an amount the datasheet does not state.
Some publish a typical figure and name the test behind it. Amazon’s eero publishes 4.5W for an eero 6+, measured to the CTA 2049-A test. That is a usable number, and at £10.38 a year it is the lowest published figure in that category.
Most publish nothing. When we checked the bestselling mesh systems in September 2026, no Amazon listing stated a power draw at all, and at least one maker gave only the adapter rating, 12V at 1.5A, which caps the unit at 18W and says nothing whatever about what it draws in use. We checked TP-Link’s UK product page for the Deco M4 again on 26 September 2026 and it still publishes no power consumption figure of any kind.
That is the always-on blank: a device that runs every hour of the year, sold without the one number that decides what it costs to own. The gap is not illegal. The regulation sets a ceiling the device must stay under. Nothing requires the figure to be printed on a retail listing.
Why a maximum is not a running cost
This is the mistake the category invites, and we have made a point of not making it. Pricing a 15W maximum for every hour of the year gives £103.75 for a three-pack, which is a true ceiling and a misleading forecast. The EU Code of Conduct on broadband equipment, a voluntary efficiency benchmark, allows a home gateway 2.3W to 3.0W when idle plus roughly 1.7W to 1.8W for each Wi-Fi 6 radio, which suggests real draw sits well below the datasheet maximum. Where we quote a maximum, we say so, and we do not present it as a bill.
How to work out your own
Find the wattage, multiply by £2.31, and you have the annual cost. The wattage is the hard part, and in rough order of reliability you want the maker’s datasheet or support page first, the energy label second, and the power adapter rating last, because an adapter rating tells you what the device may draw and not what it does.
If none of those exist, a plug-in energy monitor measures it directly, which is the only way to close the blank on a device whose maker will not publish. Our guide to energy monitors covers what a plug-in monitor adds over the free in-home display that came with your smart meter.
For appliances that are switched on rather than idling, use the UK Running Cost Index, which prices 26 household items per hour, per use and per year at the same cap rate. For a worked example of always-on kit priced this way, see best mesh Wi-Fi systems.
Method. Legal ceilings are read from Commission Regulation 1275/2008 as retained in UK law, at legislation.gov.uk, on 26 September 2026. The electricity rate is 26.32p per kWh, the Ofgem price cap unit rate for direct debit customers from 1 October to 31 December 2026, read at Ofgem on 26 September 2026. Annual cost is watts multiplied by 8,760 hours, divided by 1,000, multiplied by the unit rate, rounded to the nearest penny. Standing charge is excluded, because it is payable whether or not the device exists. Device figures are the makers’ own published specifications, cited on the pages they come from.
What this index does not do. We have not metered any device. Every figure here is either a legal limit, a published manufacturer specification, or our arithmetic on one of those, and each is labelled as such. Where a maker publishes a maximum rather than a typical draw, the resulting cost is a ceiling and is described as one.
Next revision. Rebuilt when Ofgem revises the price cap, next on 1 January 2027. The device audit is expanded at each revision.
Cite this. Look Into, UK Always-On Load Index, 26 September 2026. https://lookinto.co.uk/energy/uk-always-on-load-index/
Free to reproduce with attribution and a link. The cost figures are Look Into analysis derived from the retained Ecodesign standby limits and the Ofgem cap unit rate for 1 October to 31 December 2026. Keep that basis with the figure, because a cap rate without its date stops being a fact.
Sources
- Commission Regulation (EC) No 1275/2008, ecodesign requirements for standby, off mode and networked standby, as retained in UK law with amendments to 31 December 2020. legislation.gov.uk, read 26 September 2026.
- Ofgem, energy price cap unit rates and standing charges, 1 October to 31 December 2026: electricity 26.32p per kWh, 54.83p daily standing charge, direct debit. Read 26 September 2026.
- TP-Link Deco X10 EU datasheet (October 2023), Deco X55 EU datasheet (April 2024), Deco BE3600 EU datasheet (June 2025), for maximum draw figures. TP-Link UK product page for the Deco M4, checked 26 September 2026, which publishes no power figure.
- eero support documentation for the 4.5W typical figure for the eero 6+ and its CTA 2049-A test basis.
- EU Code of Conduct on Energy Consumption of Broadband Equipment, for the idle allowance figures quoted as a benchmark.