What an appliance really draws, moment by moment, and what it accumulates over days — which is the number every system-sizing calculation needs. It measures a mains appliance at the socket, so it complements rather than replaces a DC clamp meter or a shunt monitor.
The cheapest instrument on this shelf answers the question that decides the size of everything else.
What it measures
Voltage and current at the socket, from which it reports power now and energy accumulated. Many also report a cost, a running time and a power factor, which is informative on anything with a motor.
Why the accumulated total matters most
A load list built from labels is built from maximum ratings. A load list built from measured daily totals is built from what actually happened. The difference decides battery size, panel size and whether an installation keeps up — and it is usually large.
What it cannot do
It sits on a mains socket, so it says nothing about the low-voltage side of a system. Direct-current loads need a clamp meter or an in-line shunt, and a whole-bank picture needs a monitor that counts continuously.
The measurement worth taking first
The fridge, for forty-eight hours, in conditions like the ones it will live in. Everything else in an off-grid budget is smaller and easier to estimate, and the fridge is the one that is routinely estimated wrongly in both directions.
What people ask before they order
Why is the accumulated figure the important one?
Because cycling appliances have no single draw. A fridge’s instantaneous reading swings between nothing and its full compressor current; only the total over a day describes it.
Can it measure a starting surge?
Rarely well. A surge lasts a fraction of a second and most plug-in meters sample too slowly to catch its peak, which is a job for an instrument with a peak-hold function.
Last reviewed 16 September 2026