Ah, I didn’t realise that you could do that, in which case an absolutely standard installation (as far as the emonTx and emonCMS itself is concerned) will be fine. Given power values, emonCMS can process those into accumulated Wh or kWh and store those. The data format is our own, fully documented in the ‘Learn’ section here. Learn→Electricity Monitoring→Timeseries
That is what I anticipated. “what impact” - in short, I think a very bad one - quite possibly fatal for the card and any data on it, so a UPS that can do an orderly shutdown of the Pi would be a very sensible precaution, probably necessary. And I presumed that accurate time stamps would be at least desirable, if not necessary also.
I’m not sure how the PHPFINA database would cope, I suspect you would need the timeseries one. @TrystanLea ?
I was drives and controls principally, before I retired. Some knowledge is the honest answer. Setting up emonCMS is reasonably straightforward once you’ve cracked the basic thinking, but I’m not an emonCMS expert, so I can’t tell you too much about the niceties and details. And a basic knowledge of the ‘C’ language will help when customising the emonTx.
As for others using - it depends on how good the instructions are and what they will be doing! If it’s a matter of taking the SD card out of the Pi and putting a new one in, then all they really need to know is not to pull the card out until the Pi’s been shut down properly, which can be done from the Web interface, or which an intelligent UPS should do for you.