Glyn, I’ve got to point out that shortening the transmitted message can also result in worthwhile savings.
The ‘standard’ message is 4 powers, the voltage, 6 temperatures and a pulse count. That’s 26 bytes of payload + 9 housekeeping bytes = 280 bits. At the standard data rate of 49 kb/s, this takes 5.71 ms to transmit drawing 45 mA in the process - just for the transmitter, forgetting the processor needs to be kept awake as well. If that transmitted packet is reduced to remove unused variables, that burst of power can be more than halved, in the extreme case.
Let’s say in the extreme case it is just measuring 2 currents, and only power is displayed in emonCMS, then the message could come down to 2 powers only: 4 bytes + 9 housekeeping = 104 bits taking 2.12 ms. Transmitting every 10 s, the saving amounts to about 0.4 mAh per day. Yes, I did pick the most extreme case, but it illustrates the point.