How this standby power calculator works
“Standby power”, “phantom load” or “vampire power” is the electricity devices draw when they look switched off, or while they sit idle waiting to be used. Individually the numbers are tiny, but they run 8,760 hours a year, so a few watts become real money.
The calculator lists 18 common categories of always-on devices, each with a typical measured standby wattage and a typical number of hours per day spent in standby. You enter how many of each you own. For example, a cable or satellite box with recording draws around 15 W for 20 hours a day; a smart speaker 3 W for 24 hours; a modern TV just 0.5 W. If you have measured your home’s baseload with a plug-in meter, you can add any unexplained watts as measured extra standby.
Everything is added up and converted into kWh, money and CO₂, then compared with your total annual consumption. The calculator also estimates how much you could save by switching off a share of those devices with smart plugs or switched power strips. The Wi-Fi router is excluded from the saving because most households keep it on.
The formula
Average phantom load (W) = E_standby × 1000 ÷ 8760 Cost = E_standby × electricity price Saving = (E_standby − E_router) × share switched off × price
Worked example: a typical connected household
The defaults describe an ordinary home: two modern TVs, a cable box with DVR, a game console in instant-on mode, a soundbar, two smart speakers, a desktop PC and monitor, a printer, a router, four chargers, two appliance clocks, a coffee machine, a washing machine and dishwasher left on, four smart-home gadgets, an electric toothbrush and 5 W of miscellaneous controls.
Together they draw an average of 69 W around the clock, or 600 kWh a year. At €0.25/kWh that costs €150 a year (€12.50 a month) and emits about 210 kg of CO₂ on a 350 g/kWh grid. For a household using 3,000 kWh a year, that is 20% of the electricity bill.
The ranking tells the real story. The two TVs together cost under €2 a year, while the cable box alone costs €27 (110 kWh), followed by the router (79 kWh), the game console (77 kWh), the smart speakers and the smart-home devices (53 kWh each). Switching off 70% of the non-network load with €40 of smart plugs saves about €91 a year, paying back in about 5 months.
How to read the results
- Standby cost per year is the money you spend on devices doing nothing useful.
- Average phantom load is the continuous wattage you should see on a smart meter at 3 a.m. with everything off. Cross-check it against a real reading.
- Share of your electricity puts it in context. Below 5% is good; above 10% means there are worthwhile targets.
- Possible saving and smart plug payback tell you whether automation is worth buying.
- The doughnut and table rank devices by annual kWh, which is what matters, not by wattage.
Typical values
| Device | Standby / idle power | kWh per year (approx.) |
|---|---|---|
| Modern TV (true standby) | 0.3–0.5 W | 2–4 |
| TV with quick-start / networked standby | 8–20 W | 60–150 |
| Cable / satellite box with DVR | 10–25 W | 75–200 |
| Game console, instant-on | 8–15 W | 60–110 |
| Wi-Fi router + modem | 6–15 W | 50–130 |
| Smart speaker | 2–5 W | 15–45 |
| Desktop PC (sleep/off) | 1–5 W | 7–40 |
| Inkjet / laser printer (ready) | 2–15 W | 15–120 |
| Phone charger, no phone | 0.1–0.3 W | 1–3 |
Tips to cut standby waste
- Turn off instant-on modes. Consoles and TVs often ship with “quick start” enabled; switching to energy-saving standby cuts 10 W or more per device at the cost of a few seconds of boot time.
- Put the TV corner on one switched strip so the TV, set-top box, soundbar and console go off together.
- Schedule smart plugs for printers, coffee machines and home-office equipment so they are off at night and at weekends. Note that each Wi-Fi smart plug draws about 1 W itself.
- Ask your provider for a newer set-top box or replace it with streaming on the TV, which may eliminate a 15 W box altogether.
- Measure your baseload once a year and look for anything that has crept up.
- Lighting is the next quick win: check the LED savings calculator, then see your whole bill in the electricity bill calculator.
Limitations
Standby wattages vary widely between models and firmware versions; the defaults are typical measured values, not guarantees. The hours in standby per device are assumptions you cannot change individually. If a device is used much more or less than usual, adjust its count or use the appliance energy cost calculator. Routers, alarms and boiler controls provide useful services, so their consumption is not pure waste. The saving assumes devices are fully disconnected when switched off; smart plugs themselves add about 1 W each, which the payback figure does not deduct.
Method & assumptions
Annual standby energy = Σ count × standby watts × standby hours per day × 365 ÷ 1000. Cost = kWh × price. Saving assumes the chosen share of non-network devices is fully switched off with smart plugs or switched power strips.
Frequently asked questions
How much electricity does standby power waste?
Which devices use the most standby power?
Does a phone charger use electricity when nothing is plugged in?
Is it worth unplugging appliances?
How do I measure my standby power?
What are the legal limits for standby power?
Sources & references
Embed this calculator
Free for blogs, installers, schools and NGOs. Copy the code below; it updates itself automatically.