greenhouse heat

[slippery_biscuit]

I read a post recently but I'm not sure where now. Went out the other morning and the temp inside was 35 deg F. I knew the circuit powering the lights and heaters was maxed (I had tapped a circuit from that end of the house), and it had tripped the breaker.

I rerouted an unused 240v line and bought a used elec. wall heater rated up to 2400 watts. Picked up an old temp power circuit box and wired everything up.

The heater is working just fine and I'll rewire the MH light to 240v soon.

Question: Heat requirements for this greenhouse calculate out to 12000 Btu's and I am wondering if that elec heater is going to be sufficient to suffice? It seems to be adequate keeping the greenhouse at 65 deg when it dropped into the high 20's recently.
thanks, Jeff