Smart Plug Power Monitoring UK 2026: Find £200+ in Vampire Loads

Published 13 May 2026 · 9 min read

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You already have six smart plugs in a drawer. A pair of Tapos from 2022, a Hive plug that came with something, two Meross from a Black Friday twin-pack, an Aqara you never paired. You've used them to turn a lamp on at sunset. You have never once opened the "energy" tab in any of their apps.

This guide is for you. The plugs you already own can tell you, to the watt, how much electricity your house is wasting while you sleep. A weekend of methodical plug-rotating typically uncovers £200–£500 a year of standby power that nobody asked for. The kit cost to find it is £0–£75. The payback is measured in months.

TL;DR

  • Every 1W left on always-on costs about £2.16 a year at the April 2026 Ofgem price cap (24.7p/kWh).
  • A typical UK household has 60–200W of vampire load running 24/7 across entertainment, kitchen, office and heating circuits.
  • That's £130–£430 a year of electricity for things you aren't using.
  • A Tapo P110 smart plug costs about £15 and measures real-time draw to within ±1W.
  • Rotate one plug around the house for a weekend, log the worst offenders, automate them off. Payback in 2–4 months.

The conversion factor you'll use all guide

At the April 2026 Ofgem cap of 24.7p/kWh for electricity:

1W left on continuously for a year = 8.76 kWh = £2.16

Keep that number in your head. A 50W idle draw is £108 a year. A 100W idle draw is £216 a year. A 200W heated towel rail left on year-round is £432 a year, which is more than most people's smart-home budget for the next decade.

The conversion is the whole point of energy monitoring. Without it, "the TV uses a bit when it's off" is a shrug. With it, "the TV setup uses 65W when it's off, which is £140/yr" is a decision.

The smart plug shortlist

Three plugs do the job well in a UK Home Assistant setup. Everything else is either inferior on accuracy, locked into a vendor cloud, or both.

TP-Link Tapo P110 / P115 — the default choice

About £15 each, often cheaper in twin-packs. Built-in energy monitoring accurate to ±1W. Integrates with Home Assistant via the official TP-Link integration — works locally on your LAN once configured, no cloud dependency for the live power reading.

The P110 is the standard 13A UK plug; the P115 is a slimmer variant that fits double sockets without blocking the second outlet. Functionally identical. Buy the P110 here or the slimline P115 here.

Shelly Plus Plug S — best Home Assistant integration

About £18 each. Native local API, optional MQTT, no cloud account required. The Shelly is overkill for a one-off audit but ideal for the plugs you'll leave in place permanently on the worst offenders. Shelly Plus Plug S on Amazon.

Aqara Smart Plug — if you're already on Zigbee

About £25. Requires a Zigbee coordinator (an Aqara hub or a ZBT-2 stick on your Home Assistant box). Cleaner if you're already running a Zigbee mesh; pointless if you aren't.

What to avoid

Cheap no-name plugs that report energy only through a vendor's Chinese cloud app. They tend to drop the connection, round draws to the nearest 5W, and have no path into Home Assistant. The £8 saving isn't worth the data quality.

The vampire-load offender list

Typical idle draws from UK Energy Saving Trust data and field measurements. Numbers are "when the device is doing nothing you asked it to do" — TV off, console asleep, microwave clock running, nobody in the room.

Entertainment

  • Sky Q 1TB box (active standby): ~18W. The 2TB model: ~26W. Both drop to 0.4W in full Eco mode but Sky's Eco only runs roughly 02:30–05:45.
  • Older set-top boxes (Virgin TiVo, BT YouView): 8–20W standby.
  • PS5 / Xbox Series X in "instant on" rest mode: typically 1–10W with network features on (much lower than people think), but jumps to 10–25W if USB charging or background downloads are active. PS5 on the home menu idling draws ~45W, so the costly state is "left switched on", not "rest mode". In proper off, 0.5W.
  • Smart TV in true standby: 0.3–1W. In "quick start" mode: 10–30W.
  • Soundbar / AVR idle: 2–5W. Older AV receivers: 15–40W.
  • Games console with hard drive spinning down: add 5W intermittent.

The entertainment unit is almost always the single worst circuit in the house.

Kitchen

  • Microwave with clock display: 1–3W.
  • Bean-to-cup coffee machine in "ready" mode: 30–60W. Real money.
  • Kettle (LED ring on): 2–4W.
  • Older American-style fridge-freezer: averages 80–150W; not technically vampire but worth measuring against a new A-rated equivalent.
  • Toaster, blender, stand mixer: effectively 0W when not in use. Don't bother.

Home office

  • Desktop PC in sleep: 3–8W. With monitor in standby: add 0.5–1W.
  • Laser printer idle: 5–15W. Inkjets: 2–4W.
  • Mesh Wi-Fi node: 8–14W per node. Don't turn this off — it's essential infrastructure.
  • Phone/laptop charger with nothing plugged in: 0.1–0.5W. Genuinely not worth chasing.

Heating, water and garden

  • Electric heated towel rail left on year-round: 50–200W. This is often the biggest single line in the audit.
  • Combi boiler in "summer mode" with pump cycling: 5–15W average.
  • Pond pump running 24/7: 30–100W.
  • Aquarium (heater + pump + lights): 30–200W depending on tank size.
  • Heated pet bed/mat: 15–40W.
  • Older garage door opener idle: 3–7W.

Worked household audit — Bristol semi, one weekend

A real-shape example. Three-bed semi, family of three, electric bill around £1,400/yr. They already had four Tapo plugs from previous purchases and bought one more (£15) to round out the audit.

Plan: one plug stayed on each suspected circuit for at least 12 hours, ideally overnight, while everything was "off". They logged the lowest stable reading.

Findings:

  • Entertainment unit (TV + Sky Q + soundbar + PS5 in instant-on): 65W idle. = £140/yr.
  • Home office (desktop sleep + monitor + laser printer + powered USB hub): 28W idle. = £60/yr.
  • Kitchen worktop (microwave clock + bean-to-cup ready-mode + kettle LED): 38W. Coffee machine alone was 32W. = £82/yr.
  • Electric towel rail in airing cupboard, left on year-round on the bathroom thermostat: 80W average. = £173/yr.
  • Mesh Wi-Fi (three nodes): 32W across all of them. Essential — left alone.
  • Pond pump in the garden: 45W, 24/7, March–October. = £64/yr seasonal.

Total vampire load found: 288W. Total eliminated or scheduled: 256W (left only the 32W of mesh).

Annual saving: roughly £456.

Kit cost: 5 × Tapo P110 = £75. Payback: 2 months.

The single biggest find was the towel rail. The bathroom thermostat had been ticking it on for an hour every morning since 2019; nobody had questioned it. The smart plug didn't fix the towel rail — a £0 schedule change on the existing thermostat did. The plug made the cost visible enough for someone to bother.

The two-stage workflow

Stage 1 — Audit (one weekend)

  1. Pick one Tapo P110. Plug it into the suspected worst circuit (your entertainment unit).
  2. Make sure everything on that circuit is "off" in the normal sense — TV off, console asleep, nothing playing.
  3. Wait 30 minutes for any "spin-down" current to settle, then read the live power figure in the Tapo app or Home Assistant.
  4. Note the wattage. Multiply by 2.16 for the annual cost in £.
  5. Move the plug to the next suspect circuit the following evening.
  6. By the end of the weekend you'll have 4–6 numbers and a clear list of offenders.

Stage 2 — Permanent monitoring (ongoing)

Leave plugs on the two or three worst circuits and put them behind automations. Set up the Home Assistant Energy Dashboard so the long-term cost is visible whenever you look. Anomalies — a number creeping up over months as a fridge ages, for example — will then catch your eye before they hit the bill.

Four Home Assistant automations worth building

These all assume the offending circuit is on a smart plug exposed to HA as switch.entertainment_unit etc.

1. Kill the entertainment unit overnight (except when Sky Q is recording). Trigger at 01:00, condition "Sky Q is not currently active", action turn off plug. Reverse at 06:00.

2. Office printer business hours only. Turn off at 19:00, on at 08:00. Weekend: off entirely.

3. Towel rail off when nobody's home. Trigger on person.everyone away for > 4 hours, action turn off plug. Reverse on first person home + condition "current time is between 06:00 and 22:00".

4. Baseline-drift alert. Use a statistics sensor to track each plug's average idle draw over 7 days. If today's draw exceeds the trailing average by >50W, send a notification. Catches a failing fridge compressor, a printer stuck in warm-up, a heater someone left on.

These are 10-minute jobs each in the HA UI. No YAML required.

What's not worth chasing

Be honest about the things that don't move the needle:

  • Phone and laptop chargers with no device attached: 0.1–0.5W. £0.20–£1/yr. Ignore.
  • Modern TVs in true standby: under 1W. EU regulation already caps this.
  • Mesh Wi-Fi: essential infrastructure. Turning it off saves £25/yr and breaks everything else.
  • The smart plug itself: ~0.5W. Worth it many times over for the data it produces.

The 80/20 of vampire loads is heating, entertainment and coffee. Spend the audit weekend there.

Verdict

For £15–£75 of smart plugs and one structured weekend, the typical UK household saves £200–£500 a year. The payback is faster than any other smart-home upgrade — faster than a heat pump, faster than solar, faster than a smart thermostat. The only kit that gives this return is the cheapest kit on the list.

The catch: it requires you to actually do the audit and then change behaviour or build the automations. The plugs alone save nothing. That's where managed Home Assistant earns its keep — habbb sets up the Energy Dashboard, builds the four automations above against your real plugs, and surfaces the baseline-drift alerts so the saving is automatic instead of aspirational. See how habbb works.

Where to go next