If your GH is well insullated, an electric heater would probably keep it nice and warm all through winter, even in our cold Z-5. But again; only if you insulate very well, including the floor, but for such a small space, laying down sheets of heavy black plastic with some insulation between them should be easy enough and would keep a lot of the worst of the ground cold at bay.

You would also need to seal it well from the intrusion of cold air, and for that, bundling it up in a clear solar pool cover would be an excellent option: most all of them are on sale now too.

If electric heat is what you want, using a heat pump or runing an air conditioner backwards is the most efficient.

Please google theoy of "heat pump" operation.

dcarch

Their has been considerable discussion about this. Have you done a search ?????

This thread will undoubtedly start a debate again but for me it was an easy decision.

The argument goes like this If you have Electric heat it is expensive so you must have a air tight well insulated GH to reduce cost.

With Gas you must cut a hole and allow air to blow through to avoid asphyxiating your plants so it then comes down to which is cheaper to heat.

A drafty GH with large heat lost or heat a efficient one with electricity.

Where I live you must place a gas tank far away from other buildings that means a considerable cost for burying copper line, ( Anyone priced copper lately ) or you can use the little container that will only last a couple day's.
I live in a rural area and I would have to drive 25 miles round trip every time I needed a fresh tank.
The cost of going to get a tank every few days plus changing one in the middle of the night when it was Zero made it an easy choice for me.
$14.00 for a Holmes heater and a heavy extension cord and you have heat.
You need electric to run the grow lights-heat mats -exhaust fans just wire a little heavier and go all electric.
My GH cost less than $30.00 a month in Jan and Feb. our coldest months.
No freezing changing tanks driving around to get it filled just seal it air tight put on a thermal blanket set the thermostat and forget it.

I even already have gas heat in my home but the LP tank is 150 feet away from My GH but if you live where you are allowed to place a large tank next to the GH and don't mind looking at that thing instead of flowers around the GH like mine is then I guess it would be OK just check on it often in cold weather to make sure the wind didn't blow the pilot light out.
Talking about losing heat I put an extra electric heater in my GH and set the thermostat a little lower that way if the primary heater fails I will only drop a couple degrees then the backup will come on.
I have lived in this location for 38 years and the electricity has only been off more than an hour one time and that was back in 1967 ice Storm but things are underground and more reliable now.

I tried one of those cheap milk house style heaters from Rural King got it for 12 bucks but it only lasted a few months.
I have a HOLMES that has lasted for years and it is still going so I just bought a new HOLMES for 14 Buck's at WAL-MART.
Much more to consider than just the cost of gas VS Electric
You need to think about how often will you need gas where do you have to go to get it.
Can you buy it in the middle of the night when you forgot to check it and you run out.
What is it Worth to not worry about running out of gas or not changing bottles in the cold not worrying about the pilot light going out.
All these things come into play while deciding.
I went with Electric heat and after using it for 4 years I convinced that for me it was the right decision.

Figman

Both our Rion and our HF are heated with small electric heaters. Like the others said; who wants to make a panic trip to town looking for Gas in the middle of a 10F night. We also have a back-up kerosene heater for emergencies but seldom lose the electricity here anymore.

Hi,

We were going to go with LP but after reading here and doing some investigating, we decided natural gas would fit us. We have a friend who was able to hook us up with the line and the fittings. We couldnt pass it up. LP would have been too exspensive at least here. Barb

Vented propane here, 1500 gal tank, monthly fill, can't lose heat if the power is out.

What I tried to point out in my first post and maybe failed was that each person has to look at their options.

Natural gas would probably be the cheapest heat but a lot of people will be like me and not have natural gas available.

Check on what is available what is the installation cost and how many months will you be heating the GH

I use mine to start plants from seeds so it is used about three months out of the year and half of that time I'm more concerned with cooling rather than heating.

Do you have the skill to wire correctly for electricity or will you need to hire it done.

Can you install the LP or will you hire it done.

What is the best choice for me may not be the best choice for you

It is not what others are happy with but what would be best for YOUR GH.

You need to think about the convenience which for me is a big factor in my decision.

For me it is electric for others it may be something else.

As gardener wrote: "for others it may be something else." We each have our own, unique situations.

Wrapping bales of straw in plastic, then stacking them around the GH foundation is another means of insulating, but in addition to and not a replacement for the pool cover.

What you spend up-front for insulation will pay itself back in energy savings faster than you might imagine.

Is it really safe to use a heater not specifically designed for use in a greenhouse? It seems most people use them, BUt I am having a hard time convincing my husband that we don't need to spend 150 bucks on a special heater. I will invest the money to buy a good extention cord.

Birdwidow,
Thanks for the input. I never even thought of straw bales. Excellant advice. I placed mulch around it but the idea of straw bales is much better. Thanks

rosepedal: Wrap the straw in plastic to keep it dry, and toss some moth flakes in, to repel mice. The straw will be as good as new in spring, and you can use it to mulch your veggie beds.

Your husband is right. Buy a quality heater that will be safe in the wet of a GH. It will last longer too, so in the end, will be cheaper, not more expensive.

My DH is an electrical safety nut too, which is fine with me. I'm no more keen on getting fried in my GH than he is to have to learn to cook his own meals.

BTW: On electrical safety: if you must use an extension cord, after you make the connection, use a freezer bag cut open into a flat sheet, then wrap the plugs and seal it all with very strong, waterproof tape.

lalameija,
"most people use them". Actually, most people do not use "unvented" gas heaters in their greenhouses. Please see earlier posts, check search, in this regard.

Towards the end of the summer, i bought a Dayton 240V heater for the greenhouse on ebay which was about $30 cheaper than the greenhouse online stores. I decided that after using Kerosene heating the past few years, i wanted to get something less stinky. I live in Southern New Jersey (winslow twp) which is 7Z due to our close proximity to the ocean and recently the temps at night have been around 37F. Last night it went down to 27F and the electric heater kept the greenhouse between 48F-52F and that is on the lowest setting. Plus it heats it up quick. Now i don't have to worry about rushing home after work to heat the greenhouse before it falls below freezing. It just kicks on by itself and i don't have to worry. However, i do have kerosene as backup just in case. But the power seldom goes out here even in the worst Nor'easters... If you have any questions just let me know and good luck in your winter greenhousing!!
Steve

In zone 5 your going to need a gas heater or it will cost you both arms and both legs.

A lot depends on who supplies your juice. Coal, water, or nuke.
My power bill is very reasonable. During the hottest part of the summer my biggest bill was $115.00

OneeyedJack and the Fawg

Thats alot Dog for summer. I dont spend but a very little in the summer to cool my GH to 80 degrees. I never see my electric bill change that much. Remember too your in a zone 7 and figman is in zone 5, there is a big difference in winters, also depending on the greenhouse, it could be a nightmare. Then again, if its a little thing like alot of them are, it might not be that bad.

I have been noticing a trend on here the last few year. Greenhouses are getting smaller and smaller, some of them are smaller than closets in the house.

Apparently their is a big difference in the price per kilowatt or people are not insulating very well because I live in Northern Indiana and it really gets cold here and my 10x12 hfgh don't cost much to heat.

The pumps in my pond cost more to run in the summer than heating the GH in the winter.

gardenerwantabe...its the size of the GH and max night temp that matter the most in determining cost. The little small houses wont cost that much at a low temp. Someone with a tropical temp and bigger house, will cost more.

OD,
Clearification needed. That power bill was for where I live. I still do not have a GH completed as yet.

1eyedJack and the Dawg

I've been using an unvented propane heater for several years,and If works great!!Here in north Georgia,we lose power for at least 3 days about every 2 years due to ice storms.Just one night of this would be a total loss on every plant.My greenhouse is a 14' x 20',and I use about 150 gallons of propane a year-Just fill it up the 250 gallon tank in late summer I'm done ontil the next growing season.I grew nearly 500 plants last year-and they all thrived.Propane has turned out to be the perfect solution for my situation.Mark