Regarding Gas, this makes a great deal of moisture in the air, so will need
well ventilating, which rather negates the purpose.
As far as electric is concerned, assuming you are aware of the saftey needs,
3Kw sounds a bit OTT, I have used a 700w convector heater this year, on a
timer, 1 hour on 1 hour off, even with -5c havent lost any plants or
seedlings yet.
regards
Cineman


"Redrose" wrote in message
...
Hello, at the moment I am heating my greenhouse by a 3 kw Electric heater.
but
the electric bill is getting rather large!

I am thinking of switching to a Propane Gas heater of 2 - 3 kw, has
anybody any
thoughts about this?

Thank you,

Tony.