The other night I was awoken at 3am by a single beep from the smoke alarm. I got up and did a walk through of the house and didn't find anything on or smell any smoke. I was expecting to find the oven had been left on or something. Still nervous, I flipped the breaker off on a circuit that runs the tub jets because I had previously observed when the breaker is initially turned on, there is a huge spike in electricity consumption. It's got to have a vampire load.
I got back in bed and looked at the electricity consumption chart from my phone.
Every 2 minutes, consumption spiked by about 1,200 watts for 8 seconds. That had to be a heating element kicking on. Looking back through the charts, it seemed the spikes had begun 2 days earlier at 7am. That's what time my wife irons her clothes.
I opened the in-wall ironing closet and found the iron was on. It must have heated the varnish on the wood just enough to barely trigger the smoke detector. The mechanical timer on the outlet sticks so it never shuts off. Usually my wife unplugs the iron, but not this time.
Pretty neat to troubleshoot a single smoke detector beep from bed. I had not envisioned home energy monitoring being useful for preventing the house from burning down.