Because I just have to know things, I wanted to do this too!
I had an energy audit when I first got my tub in 2005 because shortly after setting it up, my electric bill went up almost $100.00 a month!! The auditor flipped out when she saw my "giant hot water heater on the deck"!! Still, the bill should not have increased by that much!!! I talked for a long time with professionals on here who tried to help me look at my old freezer, light bulbs, etc. Finally I figured it out and it had nothing to do with the hot tub!(well maybe in an indirect way). I have a well and there was a leak at the top of the connection of the pump and my water line so that 220 line continuously pumped water day and night! This may have happened as a coincidence when we filled the tub! If I had some sort of monitoring system, I could have figured this out pretty fast!
Here is what I do now when I wonder about my electric bill and try to pinpoint high usage. My electric company PECO in Pennsylvania allows you to look at your usage with accuracy to the hour through their website. So I can see when the pumps come on (and if the heat comes on too) because it is set to filter at certain times. Recently I needed to target the surge in KWHs and after realizing that the usage was totally random, I remembered the dehumidifier that I had cranked up in the basement!
So there is a good reason to want to monitor your usage...at least I think so. I have added a spa blanket to help with insulation in my tub (probably the only one on here who uses one). And I use the economy mode when no one is using the tub for a while. So you can save $$ if you are diligent and still have your tub ready when you want to use it. Sometimes knowing it isn't the tub bumping those kilowatts makes you feel better
