Hi this is my first time grwing in winter and I have a fan heater that is costing me a bomb. I want to buy a tube heater (are these the most economical?) and I want to find out how many watts? i have a 1.2*1.2*2 meter tent and I veg with a 400w metal halide and I flower with a 600w hps, the temperatue outside the tent can go down to 10C. I grow in my spare room, I do not have central heating. Thanks fo the advice,cheers.