Smart Home Electricity Cost Calculator UK
How much electricity do your smart plugs, speakers, cameras, hubs and other smart-home devices actually use?
Many connected devices operate 24 hours a day, 365 days a year. Although an individual gadget may use relatively little electricity, a home containing dozens of always-on devices can consume considerably more over a year.
Use our free Smart Home Electricity Cost Calculator to estimate the daily, monthly and annual running cost of any electrical device.
Enter the device's power consumption in watts, how many hours it operates each day and the electricity rate shown on your energy tariff.
Smart Home Electricity Cost Calculator
Tip: check your latest electricity bill for your actual unit rate and replace the example rate above.
Estimated Electricity Usage
Estimated Running Cost
These figures are estimates based on the values entered. Actual consumption may vary because many devices don't draw their rated power continuously.
How to Use the Smart Home Energy Calculator
You only need three main pieces of information.
1. Enter the Device Wattage
Enter how many watts the device consumes while operating.
For example, if a device consumes 5 watts, enter:
5
Don't confuse watts (W) with kilowatt-hours (kWh). Watts measure power at a particular moment, while kWh measures energy consumed over time.
2. Enter How Long It Runs Each Day
Many smart-home devices remain powered continuously.
For an always-on device such as a hub, speaker or security camera, enter:
24 hours
For something operating for approximately six hours each day, enter:
6 hours
3. Enter Your Electricity Unit Rate
Look at your electricity bill for the amount you're charged for each kilowatt-hour of electricity.
The calculator uses pence per kWh.
We've included 25p/kWh as an example starting value, but you should replace it with your own tariff for a more accurate estimate.
How Is Smart Home Electricity Cost Calculated?
The calculation is relatively straightforward.
Watts × hours used ÷ 1,000 = kWh consumed
We then multiply the energy consumption by your electricity unit rate.
For example, imagine an always-on device consumes 5 watts.
Its estimated daily consumption would be:
5W × 24 hours ÷ 1,000 = 0.12 kWh
Over one year:
0.12 × 365 = 43.8 kWh
At an example electricity price of 25p/kWh:
43.8 × £0.25 = £10.95 per year
That may not sound significant for one device, but the total becomes more interesting when a home contains numerous devices operating continuously.
Example Annual Cost of Always-On Smart Devices
The table below shows how different levels of continuous power consumption affect annual electricity usage. It uses an illustrative electricity price of 25p/kWh.
| Continuous Power | Annual Consumption | Annual Cost at 25p/kWh |
|---|---|---|
| 1 watt | 8.76 kWh | £2.19 |
| 2 watts | 17.52 kWh | £4.38 |
| 5 watts | 43.80 kWh | £10.95 |
| 10 watts | 87.60 kWh | £21.90 |
| 20 watts | 175.20 kWh | £43.80 |
| 50 watts | 438.00 kWh | £109.50 |
The important point is that even very low continuous power consumption accumulates over 8,760 hours in a year.
How Much Does 1 Watt Cost Per Year?
This is a particularly useful shortcut when estimating the cost of always-on devices.
A device continuously consuming one watt uses:
1 × 24 × 365 ÷ 1,000 = 8.76 kWh per year.
At 25p/kWh, that costs approximately:
£2.19 per year for every continuous watt.
Therefore:
- 5 continuous watts ≈ £10.95/year.
- 10 continuous watts ≈ £21.90/year.
- 25 continuous watts ≈ £54.75/year.
- 50 continuous watts ≈ £109.50/year.
Change the electricity rate in our calculator to calculate these figures using your own tariff.
Do Smart Home Devices Use Much Electricity?
Many individual smart-home devices use relatively little electricity, particularly battery-powered sensors.
However, smart homes can contain numerous devices that operate continuously.
Examples include:
- Smart speakers.
- Smart displays.
- Smart-home hubs.
- Thread Border Routers.
- Wi-Fi routers and mesh nodes.
- Security cameras.
- Video-doorbell equipment.
- Smart plugs.
- Smart bulbs receiving standby power.
- Robot-vacuum charging docks.
- Smart thermostats and heating controllers.
One low-power device is unlikely to transform your electricity bill. The more useful question is how much your entire collection of always-on technology consumes.
Calculate the Cost of Your Entire Smart Home
You can also use the calculator to estimate groups of identical devices.
For example, if you have eight smart bulbs that each consume approximately 0.5 watts in standby, enter:
- Watts: 0.5
- Hours: 24
- Number of devices: 8
- Electricity rate: your current tariff
The calculator will estimate the combined annual consumption and cost.
For a complete smart-home audit, calculate each type of device separately and add the annual totals together.
Which Smart Home Devices Should You Measure?
If you're trying to reduce electricity consumption, start with devices that remain connected to mains electricity throughout the year.
| Device Type | Why Measure It? |
|---|---|
| Smart speakers | Often powered 24/7 |
| Smart displays | Display and processing can increase consumption |
| Security cameras | Often operate continuously |
| Smart hubs | Designed to remain powered continuously |
| Mesh Wi-Fi nodes | Multiple always-on devices |
| Robot vacuum docks | Remain connected between cleaning cycles |
| Smart plugs | Consume some electricity themselves |
| Smart bulbs | May draw a small amount while awaiting commands |
Rated Wattage vs Actual Electricity Consumption
For the best results, don't automatically assume that the maximum wattage printed on a power adapter represents continuous consumption.
A device rated for a maximum of 15 watts may consume considerably less during normal operation.
Power consumption can change depending on what the device is doing.
A smart display, for example, might consume different amounts depending on:
- Screen brightness.
- Whether the display is active.
- Audio volume.
- Network activity.
- Processing workload.
For more accurate figures, use measured average consumption where available.
How Can I Measure the Actual Wattage?
One of the easiest methods for plug-in appliances is an energy-monitoring smart plug.
Products such as the TP-Link Tapo P110 can monitor the electricity consumption of a connected appliance.
This allows you to measure real-world consumption rather than relying entirely on the maximum figure printed on a power adapter.
For example, you could measure a television, computer, fan or other suitable plug-in device over several days and use its average consumption in the calculator above.
See our Best Smart Plugs UK guide for suitable options.
Can Smart Plugs Save More Electricity Than They Consume?
Potentially, but only if they prevent more wasted electricity than the plug itself consumes.
Smart plugs require a small amount of electricity to remain connected and listen for commands.
If you attach one to an appliance that consumes virtually nothing while switched off, adding the smart plug purely to eliminate standby consumption may provide little or no financial benefit.
On the other hand, smart plugs can be useful when scheduling or automation prevents equipment from operating unnecessarily for long periods.
The correct comparison is:
Electricity saved by automation minus electricity consumed by the smart plug.
We'll explore this in more detail in our Are Smart Plugs Worth It? guide.
Smart Home Energy Saving Tips
If your smart-home electricity audit produces a larger figure than expected, don't immediately start switching everything off.
Instead, concentrate on devices where changes won't undermine useful functionality.
Measure Before Changing Anything
Finding a device that consumes 1 watt and unplugging it every night is unlikely to transform your electricity bill.
Identifying something consuming 30 watts continuously could be much more worthwhile.
Use Schedules Where Appropriate
Some devices don't need to operate throughout the night or while the house is empty.
Investigate High Standby Consumption
Use energy monitoring to identify equipment consuming unexpectedly large amounts of electricity while apparently idle.
Don't Disable Important Equipment
Security systems, routers, heating controls and smart-home hubs may require continuous power to perform their intended function.
Saving a few pounds isn't worthwhile if it disables something important.
Consider the Whole System
Smart-home technology can itself consume electricity while also helping reduce energy elsewhere.
A smart heating system, for example, requires electricity to operate but may potentially help reduce much larger heating costs through improved control.
See our Best Smart Home Gadgets for Saving Energy UK guide.
How Much Electricity Does a Smart Home Use Per Year?
There isn't one meaningful figure that applies to every smart home.
A small setup containing two smart bulbs and a smart speaker is fundamentally different from a property containing:
- Multiple security cameras.
- Several smart speakers and displays.
- A video doorbell.
- Dozens of smart bulbs.
- Smart heating controls.
- Smart plugs.
- Home-automation hubs.
- Mesh Wi-Fi.
- A robot vacuum.
That's why calculating the consumption of your actual devices is more useful than relying on a generic smart-home estimate.
Why Electricity Prices Matter
The same device can have a very different annual running cost depending on your electricity tariff.
Consider a device consuming 10 watts continuously.
| Electricity Rate | Approx. Annual Cost |
|---|---|
| 20p/kWh | £17.52 |
| 25p/kWh | £21.90 |
| 30p/kWh | £26.28 |
| 35p/kWh | £30.66 |
Rather than hard-coding today's electricity price into the calculator, we've made the tariff editable so the tool remains useful when energy prices change.
Smart Home Electricity Cost Calculator for Journalists and Publishers
Journalists, bloggers, researchers and other publishers are welcome to use calculations produced by this tool when discussing smart-home electricity consumption.
Please credit Crown Product Reviews and link to this calculator as the source so readers can perform calculations using their own electricity tariff.
Suggested attribution:
Running-cost calculations produced using the Crown Product Reviews Smart Home Electricity Cost Calculator.
How Accurate Is This Calculator?
The mathematical calculation is based on the wattage, operating time, number of devices and electricity tariff entered.
However, the accuracy of the final estimate depends heavily on the accuracy of those inputs.
Actual electricity consumption may vary because devices can change power consumption depending on operating state, network activity, charging, screen brightness and other factors.
The calculator therefore provides an estimated running cost rather than a guaranteed electricity cost.
Frequently Asked Questions
How do I calculate the electricity cost of a device?
Multiply the device's wattage by the number of hours it operates, divide by 1,000 to convert the result to kilowatt-hours, then multiply by your electricity price per kWh.
How much does a 1-watt device cost to run 24/7?
A device continuously consuming one watt uses approximately 8.76 kWh per year. At an example rate of 25p/kWh, that would cost approximately £2.19 per year.
How much does a 10-watt device cost to run all year?
A continuous 10-watt load consumes approximately 87.6 kWh per year. At 25p/kWh, that would cost approximately £21.90 annually.
Do smart plugs use electricity when switched off?
Smart plugs need some power for their electronics and wireless connectivity even when the connected appliance has been switched off through the plug. Actual standby consumption varies by model.
Do smart bulbs use electricity when they're off?
A smart bulb normally requires a small amount of standby power while connected to mains electricity so it can receive wireless commands. Consumption varies between products.
Do smart speakers use electricity all the time?
Yes, a smart speaker that's plugged in and available for voice commands requires continuous power. Its actual consumption can vary depending on the model and what it's doing.
What electricity price should I enter?
Use the unit rate in pence per kWh shown on your current electricity tariff or bill. Don't include your daily standing charge because that charge normally applies regardless of whether the individual device is operating.
Does the calculator include the standing charge?
No. The calculator estimates the marginal electricity cost of operating a device using the unit rate per kWh. Your household standing charge is excluded.
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