I use one of these to heat my little grow room at night
oscillating heater
It works very well at keeping the room around 21C. The fan turns itself on/off when needed too so that's a good thing. Not expensive either. I think it was around $45 or less. Oh, and it has two heat settings. 900 watt and 1500 watt. I use the lower setting.

hth
BC
budcraft Reviewed by budcraft on . Help: Heating a very small grow I am doing a super small grow in an outdoor shed for my own medicinal use. I just started flowering and it's getting pretty darn cold out there already. How can I heat this tiny space without having to heat my whole shed? The grow is only 1.5 by 2 feet but I have about 6 feet vertical clearance. I have thought about : - Super small propane heater... but how would that work? and what about humidity? - Heating blanket or 'propagation mat'... but will 40 watts of heating power make any Rating: 5