@bubbles drive safe !
I only have a 6 x 8 GH so mine is probably easier to heat. But the heat went off at 8 and then the 3' grow lights and three 65 watt fluorescent lights come on -- and that's keeping it at 54. (I do have it wrapped in the solar pool cover that Ken uses). I have all the little pepper seedlings up under the T5 grow light and it's warmer right under that. The rest of the plants can take a chill, but I'll have to monitor all day. May have to turn that heater back on before its usual time.
I have a popup 6 x 6 also with my lemon, tomatoes and jalapeno (which are all producing and actually have bees in there !) . For that I've got three 65 watt bulbs going and I've tented it with those mylar blankets. That's staying at 60. Hope it continues, as I can't add any more heaters to that one outlet I'm using !
Geeze! Just a few days ago I was figuring out how to cool it down .