Andy Burns wrote:
ant wrote:

I know the energy consumption monitor thing 'could' be a bit rubbish
but it does appear to be linear based on all the other things I've
tested...

Were all the other things you tested purely resistive loads (e.g.
kettle, incandescent lamps, heaters, oven etc)?

CFL lamps (and PCs, most phone chargers and wall warts) draw current in
a non-linear way, so are difficult to measure with the simple power meters.

These monitors are potentially inaccurate when measuring small loads and
at all load levels are only going to measure power properly on resistive
loads like kettles, electric fires etc.
The meter on which your bill is based is sensitive to both current and
voltage and the relative phases of both and so can work out true AC
power consumed.

Bob