I have five floor heaters and Sense has detected four of them in the six weeks I’ve had Sense installed. Since it detected them, I’ve become more aware of them, especially the pop that they make when they turn on and off. All five of them use different amounts of power, and it seems to be roughly proportional to the size of the floor, which makes sense. But two of them have very smooth and steady graphs, and two of them fluctuate within a narrow band for a while, and then shoot up to almost double the power towards the end.
For the one I have that’s closest to 550 watts, it’s set to 74 deg F, and is on about 600x/month for 15 minutes a time. If I’m also assuming $0.085/kWh, it would come to about $9.