I’ve slowly been discovering facts about a discrepancy over the past few days. I started discussing it in the “how have you kept your energy bill manageable” thread, but I’ve discovered enough that it probably deserves it’s own thread.
I’ve been using Sense for a bit over two months, and just tried to reconcile it to my bill. I expect some minor discrepancy as my billing cycle is based on whichever day the meter reader comes around, at whatever time they show up. Sometimes it’s a 32 day billing cycle and sometimes it’s a 28 day billing cycle. We don’t have smart meters yet, so I just have a total monthly number.
My July/August bill reads 726kWh of usage.
Sense tells me that over that same timeframe, my usage was a total of 634kWh, and my solar system generated 341.4kWh. So I would expect a net usage of ~293kWh.
Things I’ve checked/done so far:
I keep a close watch on my usage, both at the total level and the individual device level. The total is consistently the sum of the parts. Individual devices also seem to measure roughly in line with what I expect based on their labels (a coffee maker uses ~900W while on, a string of 7 LED lights uses ~60W, etc.
I’ve had a few devices on smartplugs that are detected. Sense and the smartplug consistently report back the same value, to within 1W.
I’ve compared my Enphase reporting to Sense’s solar reporting. I’ve found Enphase to report ~10%ish more power generation than Sense does. The outcomes were very similar to the other recent thread on Enphase Enlighten. This could explain a little bit of total variance, but not major amount.
The one exception to point #1 above is my Air Conditioner. We’ve been using the AC a lot in the last month. When I look at the power meter, I only see ~700W jump in usage when the AC kicks on, and no other unexplained major loads kick on while it’s running. Based on the energy rating on the AC, I would expect a ~5,000W load. The ~700W load (which hasn’t been detected yet) can be explained as being the air handler. The AC is clearly working, as we have a cool house.
Maybe I’m missing something else, but the only explanation I can think of is that somehow the AC compressor load is bypassing the mains where I clamped Sense.
Our AC does have a “Load Control Switch” on it. We don’t subscribe to the load control program, but I assume the prior homeowner did. I don’t know how this could impact the load on the main, but maybe it’s relevant?