If someone lives a small place where there are no goyim and the heater is not turned on on Shabbos (and it’s in the cold winter months) may he turn it on himself with a shinui?
Answer:
No, the heater cannot be turned on on Shabbos, even with a shinui. This will constitue a rabbinic prohibition, which is not permitted even for purposes of discomfort.
However, a timer can be used to ensure that the heater is turned on at the right time on Shabbos.