While I empathise with your predicament, my initial response was to fire off a "serve" over unreasonable expectations; but I see others have done it more nicely. If CC have a fault it is in going to market with an unfinished product. However I would prefer not to wait the 2-3 years and pay the $1000 it would cost.
One aspect that has not been covered is:
1. Compare reported electricity usage for a specific time period (say 3pm till 3pm the next day) from an envi unit to physical electricity meter.
2. Total up the precise kwh used over a time period (say 15th of june to 19th september) to a power bill quoted amount for that period.
3. Compare the average kwh per day quoted in a power bill to that of the average over a specific time period recorded by the envi.
These are the most basic and useful applications of the envi units yet it seems impossible to complete.
Basically the ENVI cannot achieve what you want. And the CC information is quite clear on this.
Firstly, if you are using an optismart there is no reason to expect it to differ from the electricity supply meter. [Automan's concerns apart].
Alternatively, if you are using clamps, the ENVI is measuring current (amps) not energy (kwh). Energy is Amps x Volts x Power Factor x time.
The voltage of your supply will vary depending on grid load and power factor varies according to the appliance drawing load. It varies from 100% for an electric heater to 80~90% for a fridge/freezer down to perhaps 10~20% for the switching power supply for your notebook. The Electricity meter takes all this into consideration, the ENVI assumes PF=100% and voltage is fixed. This is fine for looking at where you are using power and seeing relative reductions by turning things off. It will lose hands down when compared to a supply meter.
Apart from the above the ENVI is also susceptable to
- installation problems (is it on the right wire, has it missed a wire)
- stray EMF (are other wires too close)
- sampling errors (ENVI records every 6 seconds - what happened in between)
So that I am not only being negative...
If you have a smart meter or interval meter your electrical supply retailer or distributor should be able to provide you with a breakdown by time of day. I get half hourly figures from my Australian retailer on request.
If it is theft through illegal wiring have an electrical inspection done by a licensed electrical contractor.
Good Luck with your project.