The Sanyo is okay down to about -12C. It still puts out heat, but I'm not sure
how many BTUs I'm getting per watt. I don't think it's all that much.
When I see less than -10C in the forecast, I turn on the flow-through valve,
to allow oil+PV heated water to circulate in the baseboards.
If it's going to stay cold for a long time, I'll set the oil burner timer to kick
in an re-heat the water. 30 minutes on for each 90 to 120 minutes off.
If it going to be colder, (like below -15C) I just turn off the Sanyo and use a backup.
