A whole-house energy monitor will not save you a penny on its own. It is a measuring device, not a control, and the saving comes entirely from what you change after you see the numbers. That said, seeing your electricity use in real time is genuinely useful, and for some households it pays for itself several times over. Here is what these gadgets do, how they differ from the free display you may already have, and whether one is worth buying.
What a whole-house monitor actually is
A whole-house monitor clips a sensor, called a CT clamp, around the main cable coming into your consumer unit, and reports how much electricity the whole house is drawing, live, to an app on your phone. The popular ones are the Shelly EM, the Emporia Vue and the Sense monitor. Unlike a plug-in monitor, which measures one appliance at a time, a clamp monitor sees everything at once, so you can watch the total climb the moment the kettle, the immersion or the oven comes on.
How it differs from your smart-meter display
If you have a smart meter, you already have a free monitor: the in-home display that came with it. It shows your live use and your daily spend, and for most people that is enough. So before buying anything, use the display you already own. A separate clamp monitor earns its place by doing three things the free display usually cannot: it logs the data over weeks so you can spot patterns, it updates every second or two rather than every few seconds, and the fancier ones try to break the total down by individual appliance. If you will not use those extras, the free display is the smarter choice.
What they cost
A basic single-clamp monitor like a Shelly EM is around £40 to £60. A multi-circuit monitor like an Emporia Vue, which clamps onto individual circuits in the consumer unit to show which ones use what, is roughly £120 to £180. The Sense, which tries to identify appliances automatically, sits at the top end around £250 to £300. There is one catch worth flagging: fitting a clamp inside the consumer unit means working near live tails, so unless you are confident and competent, the safe versions are the ones that clamp on the outside of the meter tails, or a job for an electrician, which adds to the cost.
The honest bit: do they save money?
Feedback studies consistently find that giving people live information about their electricity use cuts consumption by roughly 5 to 15 per cent, but only while they pay attention and act on it. The effect fades if the monitor becomes wallpaper. So the saving is real but conditional. On a typical electricity bill, a 10 per cent cut is worth a meaningful amount each year against electricity at 26.11p per kWh, the current Ofgem cap for July to September 2026, which pays back a £50 monitor quickly. But that only happens if the monitor changes your behaviour. Buy one, glance at it twice and forget it, and you have spent £50 to save nothing.
What I would actually do
If you have a smart meter, start with the free in-home display for a fortnight and actually watch it. Notice what spikes the total: it is almost always the heat, the immersion, the oven and the tumble dryer, the same big users covered in what uses the most electricity in your home. If that is enough to change a few habits, you are done and you spent nothing. Buy a clamp monitor only if you specifically want per-circuit detail, long-term logging, or you are on a time-of-use tariff and want to shift flexible use into the cheap window with precision. In that case a Shelly EM or Emporia Vue is the sensible spend. The Sense, at triple the price, is for enthusiasts, not for saving money. And whichever you choose, remember the device only measures. The saving is yours to make.