I have a 'Lil Sweetie' wood box heater. I use that and have a radiant electric heater that is thermostat controlled. When the wood heater burns down, the electric kicks in. And yes, we see power outages often enough that I learned to get up a few extra times at night to keep the wood heater going.
The problem with that is the wood heater is on one end of the (10 x 20) greenhouse and a fan circulates the warm air. The fan quits when the lights go out. I staged plants that don't mind the cooler temps at the far end of the greenhouse but...
I saw a fan that sits on the wood heater and uses convection to circulate the air. Am thinking I need one of them too.
And now, the weather says we have seen our high for the day. I believe I'm going to load the heater and the fireplace just to be ready. Stay warm.