Heating efficiency

[richardb]

I run two cedar greenhouses boarded up to bench level and fully insulated internally with bubble wrap type material.
At present I use one 3 Kw fan heater in each house, keeping one house at minimum 10 centigrade and the other at 15 centigrade. I have a paraffin standby for the cool house (Odontoglossums & Cymbidiums) and a flueless propane heater standby for the warmer house (everything else is in there).

I have no problems at all with my regime, but have decided to research to find out what combination of heaters is the most fuel efficient. I only have electricity, propane, or paraffin and NO mains gas. I suppose I could instal kerosene boiler at a pinch.

My question for debate is "which TYPE of device do people find most fuel efficient". That is for example, I use fan heaters, but would perhaps electric bar heaters or electric radiators be better.
Richard

I am looking for any validated research/tests rather than opinions on this one. Any input welcome.
Richard