Smart home devices use less electricity than major appliances, but a collection of always-on gadgets can add a measurable amount to household consumption. This guide shows how to estimate the running cost of smart speakers, cameras, hubs, displays, plugs and heating controls using your own electricity rate, with practical examples and settings that can reduce unnecessary use.
Overview
The easiest way to understand smart home electricity usage in the UK is to separate the device's power draw from the price you pay for electricity. A device drawing 2 watts continuously may seem insignificant, but it operates for every hour of the year. Several devices operating around the clock can therefore become worth checking during an annual energy review.
Most of the figures below describe the electronics themselves, not the larger appliances they control. A smart plug may use a small amount of power while switching a heater or lamp, but the heater or lamp's consumption is not included. Similarly, a smart thermostat's running cost covers its display, receiver or network connection; it does not include the gas or electricity used by the boiler or heat pump.
Actual consumption varies by product, settings and network activity. Cameras may use more power when infrared night vision, motion detection or local recording is active. Smart displays can draw more while showing a bright screen. Battery-powered devices also have a different profile because their energy use is concentrated in charging rather than continuous mains operation.
How to estimate smart device running costs
Use this formula:
Annual energy use in kWh = watts × hours used per day × 365 ÷ 1,000
Then calculate the cost:
Annual cost = annual kWh × your electricity price per kWh
For a device that draws 2W continuously, the calculation is 2 × 24 × 365 ÷ 1,000, giving approximately 17.5kWh per year. At an illustrative electricity rate of £0.30 per kWh, that would cost about £5.25 a year.
Check whether the wattage on the product label is a maximum input rather than a typical operating figure. For a more reliable result, use a plug-in energy monitor for mains-powered devices. Measure over at least 24 hours, and longer if the device changes behaviour between day and night. For USB-powered products, measure the complete adapter and device combination if possible.
Do not confuse the charger rating with actual consumption. A 20W adapter can safely supply up to 20W, but the connected device may draw only a fraction of that amount.
Inputs and assumptions
The table uses broad illustrative ranges rather than claims about a particular model. The middle figure in each range is used to estimate continuous operation for 24 hours a day, 365 days a year. The three cost columns show how the result changes at £0.20, £0.30 and £0.40 per kWh. These are calculation scenarios, not a statement of current UK tariffs; replace them with the unit rate shown on your bill or tariff.
| Device type | Typical continuous range | Assumed average | Daily use | Annual use | Cost at £0.20/kWh | Cost at £0.30/kWh | Cost at £0.40/kWh |
|---|---|---|---|---|---|---|---|
| Smart speaker | 1–3W | 2W | 0.048kWh | 17.5kWh | £3.50 | £5.25 | £7.00 |
| Indoor smart camera | 2–5W | 3.5W | 0.084kWh | 30.7kWh | £6.14 | £9.21 | £12.28 |
| Smart home hub | 2–6W | 4W | 0.096kWh | 35.0kWh | £7.00 | £10.50 | £14.00 |
| Smart display | 3–8W | 5.5W | 0.132kWh | 48.2kWh | £9.64 | £14.46 | £19.28 |
| Smart plug | 0.5–2W | 1.2W | 0.029kWh | 10.5kWh | £2.10 | £3.15 | £4.20 |
| Mains-powered heating control | 1–3W | 2W | 0.048kWh | 17.5kWh | £3.50 | £5.25 | £7.00 |
Battery-powered cameras, doorbells and smart locks are harder to compare from a continuous wattage figure. Their annual electricity use depends on battery capacity, recharge frequency, temperature, motion activity and whether live video is used frequently. For these, measure the energy used during a typical recharge and multiply it by the number of recharges per year.
Heating controls deserve particular care. A battery-powered smart radiator valve may have minimal direct mains consumption, while a thermostat receiver remains connected continuously. The meaningful energy saving usually comes from controlling heating more effectively, not from the small amount used by the control itself. See our guide to smart TRVs and smart thermostat compatibility guide before buying.
Worked examples
A small smart home setup
Suppose a home has one smart speaker, one indoor camera, one hub, one smart display, one smart plug and one mains-powered heating control. Using the assumptions in the table, the group consumes approximately 159.4kWh per year. At £0.20 per kWh, that is about £31.88 annually; at £0.30, about £47.82; and at £0.40, about £63.76.
This estimate assumes every device remains at its assumed average continuously. It may overstate some products and understate others, particularly cameras and displays. The result is best used as a planning figure, then refined with measurements from the devices that matter most.
Comparing two always-on devices
A 2W smart speaker and a 5.5W smart display perform related assistant functions but have different continuous power assumptions. At £0.30 per kWh, the speaker costs approximately £5.25 per year, while the display costs approximately £14.46. If you rarely use the screen, switching it off overnight or enabling a low-power display mode may be more effective than changing the speaker.
Finding the biggest opportunity
Small networked devices are rarely the main source of household electricity use individually. However, equipment with screens, cameras, heaters or fans can become more significant. Measure those first, along with devices that are left on in spare rooms or holiday properties. A smart plug with energy monitoring can help identify patterns, but remember that the plug itself also uses a small amount of electricity.
Practical ways to reduce consumption
- Turn off smart displays, spare-room hubs and speakers when they are not needed.
- Use screen-off, dimming and night modes on displays and cameras.
- Disable features such as continuous recording or high-resolution live views if they are unnecessary.
- Review motion sensitivity and activity zones so cameras do not record irrelevant movement.
- Unplug chargers and adapters that are not needed, especially in guest rooms and offices.
- Group devices on a switched extension lead where doing so will not disable essential security or heating controls.
- Choose local automation where practical if it allows a device or camera to avoid continuous cloud streaming.
- Do not switch off safety-critical equipment, heating protection or security devices without checking the consequences first.
For a wider smart home plan, our guide to building a smart home without a monthly subscription covers ownership and running-cost considerations. If you are reviewing lighting, compare the control hardware as well as the bulbs in our smart lighting guide.
When to recalculate
Revisit your estimate whenever your electricity unit rate changes, you move to a different tariff or you add several always-on devices. It is also worth checking after a major firmware update, because power-saving behaviour and features such as recording or display brightness may change.
Make an annual household energy review by listing every mains-powered smart device, recording its measured or estimated wattage and multiplying the result by your current unit rate. Pay particular attention to cameras, displays, hubs and heating equipment. Replace the illustrative rates in this guide with the exact figure from your bill, and update measurements when you replace a device with a newer generation.
A simple spreadsheet with columns for device, watts, hours per day, annual kWh and tariff rate will keep the calculation repeatable. That makes it easier to decide whether a setting change, timer, switched extension lead or replacement device is likely to make a worthwhile difference.
