Free tool - no signup, nothing uploaded
How Much Electricity Does Your Smart Home Actually Use?
Every hub, camera, and mesh node in this house draws power every hour of the year. One device is trivial. Twenty of them, running around the clock, are a line on the bill that nobody itemizes. This calculator itemizes it: your rate, your devices, and a breakdown sorted so the biggest offender sits on top.
What does your smart home draw?
Enter the rate from your own electricity bill, then adjust the device list to match your house. Everything recalculates as you type. Results are shown in EUR.
It is on every bill, usually per kWh. The tool will not guess it for you, because rates differ by multiples between markets and tariffs.
| Device | Watts | Hours/day | Remove |
|---|
Biggest offenders first
Enter your rate above to see costs. The device list already counts your kWh: per day for the seeded devices.
How to use it
- Copy the per-kWh rate from your electricity bill into the first field. Not the standing charge, the per-unit price.
- Edit the device list. The seeds cover common always-on gear; rename them, change the wattages, delete what you don't own.
- Set hours per day honestly. Infrastructure runs 24. A TV in standby also runs 24, just at a lower wattage than when it's on.
- Read the breakdown from the top. The first bar is where a change would save you the most.
Why the tool refuses to guess your rate
Most energy calculators pre-fill a rate and quietly assume you live wherever their author does. I won't do that. Electricity prices differ by multiples between markets, and even on one street two houses can sit on different tariffs. Any default would make the output confidently wrong for most people who see it. The field starts empty because the only correct number is printed on your bill, and finding it takes thirty seconds.
Standby is the real story
Here's the part that surprised me while planning this house: the always-on layer costs more than the gadgets. The International Energy Agency launched its One Watt Initiative back in 1999 precisely because standby losses were estimated at 5 to 10 percent of residential electricity use (IEA One Watt Initiative). Smart homes make that worse before they make it better. A hub can't sleep. A camera that sleeps is a camera that missed something. My Home Assistant machine has to be awake at 3 am, because 3 am is when the interesting automations run.
The good news? The numbers are small per device. Raspberry Pi's own documentation lists the Pi 4 Model B at around 600 mA of typical bare-board active draw, roughly 3 W at 5 V (Raspberry Pi documentation). Run the calculator and you'll likely find your whole smart layer costs less per year than one careless choice, like a gaming PC left on overnight. But you won't know until you put your own rate in. Isn't that worth thirty seconds?
Estimate first, then measure
Nameplate wattages lie. A power adapter rated 15 W tells you the ceiling, not the draw, and real standby consumption is often a fraction of it. The seeded numbers here are deliberately round for exactly that reason. Treat them as a first pass, then put a metering smart plug on each suspect for a week and type in what it reports. That's how I audit devices before they earn a place in the rack, and it's the same shortlist thinking behind why this house runs on Home Assistant: measure, don't trust the box.
What to do with the answer
A sorted breakdown turns vague guilt into a to-do list. If the top bar is heating or cooling related, automation pays for itself fast; that's the whole case for smart thermostats that work with Home Assistant. If it's a cleaning robot's dock idling at full tilt, a schedule that cuts its charger after top-up is a ten-minute automation. The robot vacuums we've tested with Home Assistant expose their dock state for exactly this kind of trick.
Questions
- Why do I have to enter my own electricity rate?
- Because any number we picked for you would be wrong. Rates differ by multiples between markets, and within one market between tariffs and times of day. Your bill states your rate per kWh; that number makes every result on this page true for your house instead of an average of nobody's.
- Where do the pre-filled wattages come from?
- They are round starting points for typical always-on smart home gear, not measurements of specific products. Replace them with readings from a metering smart plug, which is the only honest way to know what a device draws in your wall. The two figures the page states as fact, the Raspberry Pi draw and the standby share, are cited in the text below with their sources.
- Why do all the seeded devices run 24 hours a day?
- Because that is the shape of smart home consumption. A kettle draws 2000 W and nobody worries about it, since it runs 6 minutes. A hub draws 2 W and runs 8766 hours a year. Standby and infrastructure are where the money quietly goes, which is why the defaults are all-day devices rather than appliances.
- Is anything uploaded or saved?
- No. The whole calculator runs in your browser. There is no account, no cookie, no network request, and closing the tab forgets everything you typed.
- How accurate is the math?
- The formula is exact: watts times hours divided by 1000 is kWh, times your rate is money. A month is treated as a twelfth of a 365.25-day year so the monthly and yearly figures never contradict each other. The uncertainty is entirely in the wattages you enter, which is why measuring beats estimating.