help on electronic energy meters

Ahh, how about sealing the enclosure the electronic meter is in using some form of anti-tamper or security sealing device. That is what is done down here.

That is what's done here as well.

They used to use lead seals on a wire loop and if you were clever enough, you could heat up the wire just barely enough so that the lead melted slightly around the wire. Then while still hot you could pull out the wire, open the meter and jump it out. Then just before the utility meter reader came by again, slip the wire back in, heat it up and when cool, the seal would re-solidify around the wire and look like new.

Now they have switched to plastic seals.

What sort of device do you have to meter the power?

you need a kilowatthour meter that you can set, it would work in a similar fashion to a parking meter, except the device will turn off after the prepaid powerhas been used up.

Energy supply companies usually have responsibility in law for the meters on their supplies. A telephone call to them would be a good start!

Discretely monitor the current flow before and after your device. If they don't match, you have a problem. If the user becomes aware of such monitoring you also have a problem. The first amp meter should be well before the device and the second immediately after the device or built into the device. The second should not be a problem as you are already monitoring the current with your device I presume. You may have to find a way to creatively route the supply current to accomplish monitoring it. This may be preferrable to a lock box in some cases because the user will not be aware of your monitor hopefully. Even if they manage to defeat your lock box for your device they will be thwarted by the evidence. Ah Ha!