Aniseed wrote:
Thank you T i m, that's just what I was looking for!

It's likely to be significantly (double the real reading) inaccurate,
the one I got from maplin is.
It works fine on simple loads like motors/heaters.

In practice, you can look up all the figures on websites.
2-300W is unlikely.

I measured my server (12 drives spinning, 1.3G duron) at around 150W.