Do Smart Plugs Save Money? An Honest Answer with the Maths

Smart plugs save money only if you act on what they show you. The plug itself does not make anything more efficient; it lets you see what an appliance really uses, switch it off automatically when it is not needed, and spot the expensive surprises. Used on the right appliances, that can be worth far more than the plug's own small standby use. Used on a phone charger or a device you never change, it saves nothing.

The honest starting point: a smart plug uses electricity too

A smart plug has to stay connected to your Wi-Fi so it can respond to the app, voice commands and schedules. That costs a little power, all day, every day.

Hypothetical example: a plug drawing 1 W continuously uses 1 × 24 × 365 ÷ 1,000 = 8.76 kWh a year. At the Ofgem price cap average for October to December 2026 (26.32p per kWh, Direct Debit, England, Scotland and Wales), that is about £2.31 a year. At the EU household average of around €0.28 per kWh in the first half of 2026 (Eurostat data reported by the Brussels Times), about €2.45.

So the test for any smart plug is simple: will it help you cut more than that? On the right appliance, easily. On the wrong one, never.

Where smart plugs pay off

Hypothetical example 1: the forgotten heater

Say a 2 kW portable heater runs one hour a day longer than anyone needs, on 120 days over winter. That is 2 kW × 1 h × 120 = 240 kWh. At 26.32p per kWh, about £63. A countdown timer or schedule that removes that hour saves far more than any smart plug's standby use. (Space heaters need a plug rated for them; our space heater running cost guide covers safe use.)

Hypothetical example 2: the entertainment corner

Say an older TV, soundbar, subwoofer and console together draw 10 W in standby, 20 hours a day. That is 10 × 20 × 365 ÷ 1,000 = 73 kWh a year, about £19.21 at 26.32p. A schedule that cuts power overnight and during work hours removes most of that. Subtract the plug's own use (up to £2.31 a year if it draws 1 W) and the net saving is around £17 a year.

Hypothetical example 3: the garage freezer

You measure an old chest freezer for a week and find it uses 15 kWh, which is 15 × 52 = 780 kWh a year, about £205. That is not a number a smart plug can switch off (a freezer must stay on), but it is the information you need to decide whether a newer, more efficient model or emptying and retiring it makes sense. Here the plug pays off as a measuring tool, then moves on to the next appliance.

Where smart plugs don't pay off

• On devices that already draw very little. A modern TV or charger drawing around half a watt in standby will cost less than a smart plug drawing up to 1 W. Adding the plug increases your bill.
• On appliances that must stay on. Fridges, freezers, heating controls and alarms cannot be scheduled off. Monitoring them is useful; switching them is not.
• On hard-wired appliances. Electric showers, ovens, hobs and immersion heaters cannot be plugged in, so a smart plug cannot help directly.
• When you never look at the app. Monitoring without action is just a graph.
• When it replaces a simpler habit. If you already switch your TV off at the wall every night, a smart plug adds convenience, not savings.

Be sceptical of big percentage claims

You will see marketing that promises a fixed percentage off your bill or a payback within weeks. Treat that with caution. A smart plug only affects the appliance plugged into it, and only when you change something. Your saving depends on which appliances you have, how you use them, your unit rate, and whether you act. The only reliable way to know is to measure before and after.

Remember too that part of your bill is a fixed daily standing charge (54.83p per day for electricity under the October to December 2026 Ofgem cap average) that no appliance change will touch. See our UK electricity bill guide for how that splits.

How to make a smart plug pay

1. Start by measuring, not switching. Put the plug on your biggest plug-in suspect for a week. Our list of what uses the most electricity at home suggests where to start.
2. Work out the yearly cost. Weekly kWh × 52 × your unit rate.
3. Decide the action. Schedule it, shorten it, change a setting, or replace the appliance.
4. Measure again for a week to confirm the change worked.
5. Leave the plug where it keeps saving, or move it on to the next suspect.
6. Subtract the plug's own use from your savings so you know the true figure.
7. Review in each season. Heaters and dehumidifiers matter in winter; fans in summer.

For more ideas that actually cut waste, see smart plug ideas and schedules.

Common mistakes

• Plugging a smart plug into every socket. Each one adds its own standby use.
• Overloading. Never put an appliance on a smart plug with a lower rating than the appliance's maximum power, and avoid running high-power heaters through extension leads.
• Scheduling things that should stay on. Freezers, routers that run your alarm, medical equipment.
• Trusting the app's cost figure blindly. Check it uses your actual unit rate.
• Expecting savings on hard-wired loads. Use your meter for those.

Where Wattly fits (and where it doesn't)

The Wattly smart plug is built for the measure-then-act approach: real-time energy monitoring with cost per hour, day, week and month and usage history in the Tuya Smart app, plus schedules, countdown timers, scenes, automations and remote on/off. Schedules are stored on the plug, so they keep running if your internet drops. Its own standby use is under 1 W, and overload protection switches it off if the load goes beyond its rating.

What it won't do: save money by itself, measure hard-wired appliances, or act as a whole-home meter. Use it on appliances where there is real waste to remove, stay within its rating (13 A for the UK version; 16 A or 20 A for the EU Schuko versions), and check your results. See the product page for the version that fits your sockets.

Related reading

• Smart plug energy monitoring explained
• Standby power explained
• How to calculate appliance running cost
• Smart plug vs smart meter