How do I read my smart meter in-home display?
The little screen shows watts, pounds, days and a traffic light, and almost nobody is told what any of them mean. What each number actually measures, and the one thing it is genuinely good for.
- Difficulty
- beginner
- Time
- 15 min
- Read
- 5 min
Short answer
The headline number is usually your current rate of use in watts or kilowatts — a snapshot of what is drawing power right now, not a total. The pounds figure is that rate projected forward, or a running daily total, depending on the mode. The single most useful thing you can do with it is switch appliances on and off one at a time and watch the number move, because that turns an abstract bill into something you can see.
The in-home display was supposed to be the part of the smart meter rollout that changed behaviour, and for most households it sits in a drawer within a year. The reason is almost always that nobody explained it. The screen mixes three different kinds of number — an instantaneous rate, a cumulative total, and a projection — and switches between them depending on which mode you are in, so a reading that looks alarming in one mode is meaningless in another. Once you know which is which, it becomes genuinely useful.
Step by step
- Identify the instantaneous reading.Usually the largest number, shown in watts or kilowatts, sometimes with a traffic light. It is a snapshot: what your home is drawing at this second. Switch a kettle on and it jumps by roughly two to three kilowatts, and drops back when the kettle stops. It is a rate, not an amount.
- Find the cumulative totals.There will be a mode showing usage so far today, this week, this month or this billing period, in kilowatt hours and in pounds. These are the numbers that relate to your bill. A kilowatt hour is one kilowatt drawn for one hour, which is what you are actually charged for.
- Treat any projection with caution.Some displays show a projected cost for the day or month, calculated from usage so far. Looked at just after cooking dinner, that projection is nonsense, because it extrapolates a peak. Judge by the actual totals rather than the forecast.
- Check gas is showing as well as electricity.Most displays cover both, usually on separate screens or with a toggle. Gas updates far less often than electricity — typically every half hour rather than every few seconds — because the gas meter is battery powered and reports periodically to preserve its battery.
- Understand the traffic light.The colour is set against a threshold, sometimes one you can change in the settings. It is a comparison against that threshold, not a judgement about whether your usage is reasonable. Many people find it more useful once they set the threshold themselves.
- Do the one experiment that makes it worthwhile.With as much switched off as practical, note the baseline. Then switch things on one at a time — kettle, oven, immersion heater, tumble dryer, shower, electric heater — and watch what each adds. This is how people discover which appliance is actually expensive, and it is far more informative than any list of averages.
- Find your standing charge in the settings.The standing charge is a fixed daily amount you pay regardless of usage, and it explains why a day with almost no consumption still costs something. Most displays show it, and it is worth knowing what yours is.
- Check the readings match your bill.The display is fed by the meter, so the totals should reconcile with what you are billed. If they consistently do not, the tariff rates programmed into the display may be out of date — that is a settings issue, not a metering one, and the supplier can correct it.
Common mistakes
- Reading the instantaneous figure as a cost — A kettle showing three kilowatts is drawing at that rate for three minutes, which is a fraction of a kilowatt hour. Rate and amount are different things, and confusing them causes needless alarm.
- Judging by the daily projection — It extrapolates whatever is happening now across the whole day, so it swings wildly and means very little. The cumulative total is the honest number.
If it doesn't work
Display shows dashes or no data
Cause: Lost its link to the meter, or the battery is flat — Fix: Plug it in on mains rather than running on battery, and move it closer to the meter. If it stays blank, the meter may have lost communications — the catalogue covers a smart meter that has stopped sending.
Costs shown do not match the bill
Cause: Old tariff rates stored in the display — Fix: The display holds a copy of your rates and does not always update after a price change or a tariff switch. Ask your supplier to push an update, or check whether you can enter them yourself.
Gas usage not updating
Cause: Normal — gas reports periodically — Fix: Gas meters are battery powered and report roughly every half hour. A gas reading that lags is expected behaviour, not a fault.
Baseline usage is much higher than expected with everything off
Cause: Something is drawing power continuously — Fix: This is the display doing its most valuable work. Look for immersion heaters, underfloor heating, a second fridge or freezer in a garage, a dehumidifier, or a lot of always-on electronics.
Display disappeared or was never set up
Cause: Common — Fix: Suppliers will usually provide or replace one, and some now offer the same data in their app instead, which many people find more useful because it shows half-hourly history rather than a live figure.
Questions people ask
Does the display cost anything to run?
It uses a trivial amount of electricity — far less than the savings most households make from understanding their usage. Running it on mains rather than battery keeps it connected and reliable.
Is the display what my bill is based on?
No. Your bill is based on readings sent by the meter itself to your supplier. The display is a convenience that reads the same meter, which is why a display with wrong tariff rates can show a different figure from the bill while the metering is entirely correct.
Can I use it to find out what is using the most electricity?
Yes, and that is its best use. Switching appliances on and off individually and watching the change tells you far more about your own home than any general list, because it accounts for your actual appliances and how you use them.