The short answer

Standby cost is average watts ÷ 1,000 × hours in that mode × days × your price per kWh. At an illustrative £0.28/kWh, a constant 5 W for 20 hours daily costs £10.22 across 365 days. Measure the actual mode and count only its hours; a device's maximum rating does not establish standby draw.

Use the standby & always-on costs calculator
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Calculate the mode you actually use

A screen that looks off does not establish zero consumption. A television waiting for a remote, a console charging a controller and a router maintaining a connection do different jobs. Treat active use, ordinary standby, network-connected standby and powered off but plugged in as separate states when their consumption differs.

Use the standby and always-on calculator to list several devices, their average watts and hours. These are estimates from your inputs; the tool does not identify connected equipment or measure your home remotely.

Energy in one mode = watts ÷ 1,000 × hours per day × use days × quantity. Multiply that kWh by your consumption-related electricity price. A mode entered for 20 hours leaves four hours for other states; it is not a complete 24-hour device total.

A worked saving, with the assumption visible

The following is an illustrative settings comparison, not a Watt & Home test or an assigned value for a product:

Assumption Existing mode Alternative mode
Average power while not actively used 5 W 0.5 W
Time in that mode 20 hours/day 20 hours/day
Period 365 days 365 days
Mode energy 36.5 kWh 3.65 kWh
Cost at £0.28/kWh £10.22 £1.02

Unrounded savings are 32.85 kWh × £0.28 = £9.198, displayed as £9.20/year. This holds active use unchanged and assumes the alternative provides the functions you need. It is not a promise that changing any standby setting saves £9.20.

Edit the current 5 W scenario and enter your own mode readings. Edit the alternative 0.5 W scenario separately to compare the mode-power assumption. Open the calculator and enter your own mode readings. If you buy a £15 control solely for this modeled saving, electricity-only payback would be about 1.63 years before the control’s own electricity use. Include that draw and any purchase cost before deciding whether extra equipment is worthwhile.

Put small watts in perspective

For a constant 1 W across all 24 hours on 365 days, energy is 8.76 kWh. At independent illustrative tariffs, that costs $1.75 at $0.20/kWh, £2.45 at £0.28/kWh, or €2.63 at €0.30/kWh. These are three scenarios, not current national prices or currency conversions.

A group can matter more than one device, but measure before assuming every item wastes a large amount. A short high-power cooking task and a small always-on load need the same kWh period for a fair ranking. The household ranking guide shows how to prioritize the larger, uncertain contributors.

Measure low power with suitable resolution

The US Department of Energy’s standby-measurement guidance distinguishes stable readings from fluctuating power, where accumulated energy over time can establish an average. Low-power measurements also need suitable instrument resolution and accuracy. A plug monitor displaying 0 W does not necessarily establish exactly zero consumption.

For a household observation, follow the monitor’s instructions and ratings. Note the exact model, enabled network and charging functions, elapsed period and meter resolution. Record enough time for the accumulated kWh difference to be meaningful. The measurement journal retains raw counter readings and conditions; its day-based records need complete measurement days. Household observations are not certified IEC laboratory tests.

Avoid duplicate hours and duplicate energy

  • A TV cannot spend 24 hours in standby and four additional hours active on the same day. State each mode’s time separately.
  • A complete-day meter sample already includes the active and idle energy captured. Do not add a standby row for those same hours.
  • If one measured power strip includes the TV, soundbar and console, do not also add each device’s full energy separately.
  • An always-on router is providing connectivity. Its operating consumption is not automatically avoidable standby waste.

Use the bill-period appliance check after matching the dates and removing overlaps. A remaining gap is a prompt to inspect assumptions and missing loads.

Read regional claims on their own terms

ENERGY STAR television criteria distinguish passive standby and network-active standby under defined tests. EU ecodesign requirements also distinguish low-power modes, with product-specific scope and dates. Neither is a universal measured value for every device already installed in US, UK or EU homes. Great Britain and Northern Ireland can have different regulatory routes; the market guide explains why a rule from one market should not be applied automatically to another.

Before switching equipment off, check which functions depend on it. For example, BT states that its hub must have power for Digital Voice calls. Apply the manufacturer’s instructions to networking, recording, charging and other services you use. The router guide helps separate service needs from arithmetic.