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I've recently bought a paraffin heater in an attempt to keep my greenhouse 'frost free'.  I'm having trouble getting the flame right.  It seems fine after I light it, and half an hour after, and when I check it before going to bed, but is very low - almost out - by morning.  And yes, I have checked there is enough paraffin :)

Can anyone offer advice?



Chuck it out and buy an electric fan heater fitted to a thermostat.

Paraffin heaters produce loads of water and always go out just before the frost hits. The water encourages mould and decay.  Most stuff in a greenhouse need to be on the dry side over winter and a fan heater which circulates air is beneficial.

Great idea, but sadly there is no way I can run power to my greenhouse 

Mike Allen

I agree with fidget regarding the drawbacks with paraffin heaters.  If the wick is not kept trimmed or is extended too high, then harmful fumes will also be a problem.  The idea is to adjust the wick so that it will produce an even blue flame.  A flickering yellowish flame will waste the fuel and produce bad results.

You mentiom the difficulty in getting electric to the GH.  If the GH is in your garden, can you not use an extension cable from house to GH.  There is another way but perhaps a bit pricy to start with.  Two 12 volt liesure batteries and an inverter.  Using only one battery connect the inverter to the battery, then plug the electric heater into the inverter.  The inverter acts in reverse to a transformer.  Thus conerting 12/24 volt DC to 230-250 volts.  Hope this helps.

I have been using a paraffin heater only in February till it warms up so I can germinate and grow on , but next year I am thinking on going on a gas heater bottled gas but I want to see witch is best and cost effective .


Mike Allen says:

You mentiom the difficulty in getting electric to the GH.  If the GH is in your garden, can you not use an extension cable from house to GH. 

See original post

 Even assuming a RCD is used, that's a potentially dangerous suggestion.  Cables running through the garden are likely to get the interest of any wildlife around during the night.  I left an extension cable out, not connected thankfully, and the next day it was in several pieces presumably chewed by foxes.  It would be possible to the insulation to be damaged but not noticed, with potentially serious results if you tried to shift the cable with the power on.

I'm in the same situation as the OP.  It's simply not practical, or affordable, to run a mains supply 100 feet down the garden.

I too would like to run electric to my GH but not a feasible option.

However, I do occasionally run an extension lead from my garage when necessary.  Usually for just a week or 2 - rarely any longer and I've never had any problem with wildlife damaging the cable.  Not saying it couldn't happen - obviously KT's experience is proof of a potential disaster.

Perhaps if the OP is prone to visiting Foxes, a system of poles to which the cable could be attached would keep the supply out of harms way.  I guess it depends how keen one is to avoid the use of either paraffin or gas.


I have over 100ft of armoured cable, sunk 9 inches deep in the ground, out of the back of the garage , along a hedge line, under a slab path into the greenhouse. It has a master off switch in the garage. It is all protected by RCD.  We put it in when the greenhouse went in, because I spent too many years playing with paraffin heaters, mould, and then losing stuff to the frost at 6 am.  The cable isn't too expensive,(google screwfix  Armoured Cable)  the back breaking bit is digging the trench.  Get a qualified electrician to fit the  Outdoor covered sockets and spur.

Hi all, thanks for your suggestions  I can't run an extension lead or put in a proper mains cable as my garden (and therefore my greenhouse!) is the other side of an access way shared with the rest of our row of houses.

Mike, the info about what the flame should look like is really helpful - the manufacturer of my heater didn't include instructions on use of the heater and I didn't know this.  I think the battery idea is interesting too

Last edited: 10 November 2017 17:45:21

Mike Allen

Firstly.  No way do I wish to cause any controversy here.  Sadly our friend is in a somewhat difficult situation.  If I may return to the extension cable method in general.  The armoured underground cable method is without doubt the best.  I had the idea of using a catanary method to get power to my workshop/shed from my dwelling.  I ended up with a plugged cable from the wheelchair out-building.  This is run through a flexible tubular casing purchased from Screwfix.  The said cable and conduit is  affixed to the high fence that runs the length of the garden to the workshop.  This powers lights and sockets in the workshop.  OK the max amps is 13.  All plugs etc are fused according to statutory recommendations.  A feed from the workshop is taken to the GH along side.  Here I have a waterproofed strip light.  Also a w/p socket for a heater of fan etc.  Thankfully no wildlife has spotted the cable.  I admit a few punctures to the hose-line.  Foxy once bit off the top of my pond fountain.  Never mind.  I would like to set a new thread on GH heating.

John Harding

There is a potential problem with the battery/inverter option. This is that inverters consume battery power at a considerable rate. I used to have a 2 Kw full sine-wave inverter in my van with a huge 'leisure battery' connected to an auto charging system from the van's alternator when I had my locksmith business. It was fine for very low power items like LED lighting and laptop computer but switch anything else on (like a key cutting machine) and the power would not last long unless I kept the engine running.

You would not be able, in my opinion, to run an electric heater even on a thermostat overnight and expect it to still be operational in the morning & I'm guessing that the power would have run out in the early hours so no frost protection there. It is extremely frustrating and expensive when you've invested time & money protecting plants only to find one failure has destroyed everything through frost damage. A small GH might be OK with a small tubular GH heater depending on the wattage of the heater but it would really pay to do some time/temperature tests before relying on an inverter. Hope this helps. John H

Mike Allen

I agree John there are problems whatever way one looks at this.  My experience of the "permanent extentension cable cas served me well for some thirty years.   I did purchase a propane gas fire.  It was of the single flame type.  It proved to be expensive to run, so it is now stored in my loft.  For several years now I have made certain my GH is well insulated and paid attention to what plants I overwinter.   I truly hope our friend manages to solve the problem.

John Harding

Hi Mike,

Yes - I too had a cable run to my workshop (used to be a garage!) and to my shed - a 10mm armoured cable protected with RCDs and a cement fillet at the bottom of at the north facing wall. From my shed I ran a lightweight JoJo reel to the GH (cable clipped to the 6ft boundary wall & fused 1 amp.) This is used solely for powering my 3 electric propagators. I also ran another extension lead to run a fan heater from w/shop to GH on a thermostat to keep the GH at 7-10 degrees when there is a risk of frost. It has proved to be effective and relatively inexpensive to run, though the initial installation expense of the 10mm armoured cable from the house to my workshop (which I needed because of the amount of machinery & equipment I use in there) did make me think long and hard - but in those days I was running a business and common sense + safety dictated it had to be done. The benefit to me now I've retired is that I have all I will ever need as regards power supply in workshop and shed.

The advice given in earlier posts is sound - viz. go for the best you can afford, even push that a little further if you can because the benefits keep backing up and 6 -12 months down the line you will be saying to yourself "I'm really glad I went the extra mile" John H


Already established that the OP can’t use electric.

Gas is probably worse than paraffin for condensation,( although I don’t know what the amount of condensation paraffin uses).  I used to work for Shell gas a long time ago, but we would tell customers that for every pound of gas burned it produces a pint of water, so the large cylinder of gas contained 104 lbs of gas, so produced 104 pints of water.  

I wonder what the OP has that needs to be kept in a heated environment, i now grow plants that don’t need heat, just frost protection, everything in my garden is from seeds and cuttings and I’ve never had any of my greenhouses heated.  My theory now is... if it’s going to cause a worry of any kind...I don’t grow it. Through this winter I will have lupins, Delphiniums, Penstemons and viola in them. 


Thanks for the advice everyone.  I'm trying to get a sort of tropical look in my greenhouse, mad I know, for the middle of Wales!!! I hasten to add, I'm not trying to grow actual tropical plants, just stuff that looks a bit like it. Cordylines, Yucca, and a few succulents at the moment.  It all just needs to be frost free.  I'd like to be able to overwinter citrus in there too.

Mike Allen

Jo I'd have thought a section of ferns more adaptable the rains of wet Wales.  Whatever my friend, enjoy your gardening.


Over time you will learn to grow what suits your garden, soil, climate etc.  Your garden will dictate to you,  not the other way round. 

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