Heaters for your greenhouse
Paraffin: Paraffin heaters are the cheapest to buy, but unless you've got a proper old fashioned garage near where you live, the fuel can be expensive. However, they have the advantage of being cheap to buy and don't require any electricity, so if your greenhouse isn't wired up they can be useful. Remember however that you've got to remember to go and light them every time that there is a frost.
Gas: Gas heaters are the cheapest to run, especially if you can mains gas to the greenhouse, but even bottled propane is a very economical energy source. They have an inbuilt thermostat, so the pilot light is lit all winter and the heater then only flares up when required. Gas heaters naturally give off C02 which is beneficial to plants, and water vapour, so if you want to create a humid atmosphere they can be usefull.
Electric: Electric heaters are the easiest to use, because you simply plug them in, set your thermostat and then leave them to it. All have an inbuilt fan which circulates the air, keeping the temperature even and the air fresh, this helps reduce disease and 'damping off' in the greenhouse. Although gas heaters are cheaper to run on 'full blast', they require a pilot light to be lit all the time and this drains the gas when not needed, the advantage of electricity is that not a bit of energy is wasted.
