"tina" wrote in message
...
Hi,

I have an 8ft x 4ft greenhouse and would like to add a heater to keep
out the cold.
I thought it best to get an OIL filled one rather than the electric
fan type.

I see they go in W rating from 1000w, 1500w, 2000w & 2500w.

Can anyone advise me what size is best?

I'm growing peas, tomatoes & carrots.

Thanks
Tina
I have heated various greenhouses for 30plus years - I have used paraffin,
butane & electricity.
Electricity may be more expensive but it is so much better & easier to use.
For the last 20 years I have used fan heaters.
My current set-up is a Bio Green Nevada 3kw fan heater which has a
distribution pipe with holes at intervals which allows even distribution of
heat. The greenhouse is 8x10 and is currently kept at 63f due to the very
accurate thermostat on the heater.
The advantage of a fan heater is that it will circulate the air eliminating
any cold spots & keeping down the mildew & fungus diseases - it can also be
used as a fan only to cool in the summer.
Parasene do good fan heaters for starters - usually available at the DIY
warehouses & garden centres.
Whilst you ask which size heater - this is not terribly relevant if the
heater has a thermostat - for the size you state I would have thought 1.5k
of greater.

Steve