Staffordshire,
United Kingdom 
Does any one use heat lamps in the greenhouse to keep off the frost, I have thought about using infra red lamps like the ones we use on the farms to keep sick animals warm, i use a fan heater at the moment but think the lamps would use less electric
16 Nov, 2010
Answers
Also, the plants need a period of darkness overnight. I use an electric g'house fan heater on a timer switch so that it only comes on overnight if the temp is low enough.
16 Nov, 2010
I have found the most cheapest so far is a small 400 watt oil filled radiator with a plug in thermometre and also I have used good quality 3 ply bubble wrap insulation this keeps my greenhouse at a nice temp without being too expensive.
16 Nov, 2010
Whilst the lamps would use less power, the advantage of the fan heater is that it creates air circulation.
Maybe you could use a combination of the two with the aid of those timer plugs....
16 Nov, 2010