In this section
Three levels
- A plug-through meter (like the Kill A Watt) tells you what one device uses. No app, no setup.
- Smart plugs with energy monitoring log a device’s use over days and can switch it off on a schedule.
- Whole-home monitors clamp sensors around the wires in your electrical panel and show every circuit in an app. They need a licensed electrician to install, because the panel’s live parts can kill.
Many utilities also show hourly use from your smart meter for free. Start there: look at the lowest hour overnight. That’s roughly your always-on load.
The always-on load
NRDC studied smart meter data from 70,000 Northern California homes and found the average home drew 164 W around the clock from devices that weren’t being used, nearly 23% of its electricity. Set-top boxes, game consoles, old desktop computers, audio receivers and recirculating pumps are common culprits. See what yours costs and how to find it.
Picks
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Emporia Vue 3 energy monitor
Seeing every circuit
- Clamps go inside your electrical panel
- Per-circuit readings in an app
Shows exactly which circuits use the most, down to the heat pump or dryer.
Watch for: Installed inside the breaker panel. Hire a licensed electrician.
Sense Energy Monitor
Detecting individual devices
- Panel-installed
- Tries to recognize devices from their electrical signature
Spots devices that switch on at odd hours.
Watch for: Device detection isn't perfect; same electrician caveat.
Kasa smart plug with energy monitoring (EP25)
Measuring one device for a week
- Reports watts and kWh
- Schedules and remote off
The cheapest way to find out what the TV, game console or dehumidifier really costs.
Watch for: 15 A max; not for space heaters.
Emporia smart plug
Pairing with an Emporia Vue
- Energy monitoring
- Same app as the Vue
Fills in single devices on circuits you can't separate.
Watch for: Wi-Fi 2.4 GHz only.
Eve Energy smart plug (Matter)
Apple Home users
- Matter over Thread
- Energy monitoring
Works locally with Apple Home and other Matter hubs.
Watch for: Needs a Thread border router, such as a recent Apple TV or HomePod.
P3 Kill A Watt P4400
A one-off check without an app
- Plug-through meter
- Shows watts and cost
No app, no Wi-Fi. Plug in, read the number.
Watch for: Small display.