Have you tried a search yet? There have been a few other threads and messages about heating these and I think you should be able to do it without running up your electric bill too much. I think someone estimated their cost was about $30/month with an oil-filled type; there are several who seem to prefer them.

My only experience is with a twinwall polycarbonate 6x8, wrapped in a solar pool cover, with jugs and bottles of water stashed here and there for thermal mass. Before I got a heater, a 500W worklight kept the chill off very well. Unable to get my hands on an oil-filled quickly, I settled for a 750/1500W convection type and am happy with it - like a radiator-type, it provides a gentle, steady heat. It has easily maintained temps at or around 50 through lows in the teens.

Yes, I think it's doable; as for the cost and whether it's worth it - that's a matter of your local energy prices and how important it is to you to get those plants growing early. Personally, even if our electric bill had risen by $100 a month, it would have been worth it, because that little greenhouse has been a delightful respite from winter!

Now maybe one of the guys will come along and give you some more objective info, lol.

Diane

If you expect any growth you would have to keep night temps in the 60's. My solution has always been to keep a soil heat cable under plants and make a grrennhouse within the greenhouse with plastic letting the heat radiated off the soil heat the smaller(just as small as the plants require) mini enviroment. The rest of the space is used for more cold tolerant species. I have used a hair dryer as heat in my greenhouse. Your 1500 watts of resistance heat produces about 5200BTUh and will cost 25 cents an hour.My rule with todays energy prices is DONT HEAT MORE THAN YOU NEED MORE THAN YOU NEED.

Sorry, I should have been more clear - I've set the heater to maintain minimum temp of around 50 degrees; that's about at the bottom of its range, just a notch above the no-freeze setting. I'm sure it could easily keep the greenhouse much warmer, but so far the lettuces, herbs, cherry tomatoes, peas and various tender plants have been lovin' it; no seedlings to worry about ... yet.

You're right, hads, no need to heat more than you need to!

cmpman, which Flowerhouse g-house do you have? I have gone on and , based on certain assumptions ( 6x6 x7 Springhouse flowerhouse, low temp -5 degF ( zone 6 minus 10 deg), greenhouse temp of 60 deg, 6mill poly cover) I reckon that on a cold night, it would take roughly 4,550 watts of electric heat to keep your greenhouse most toasty.

That would require about 3 of your typical 1500 watt heaters. Remember, this is the heat load for the coldest expected winter night. Typical night (20 deg F) you will be fine with 3,000 watts heat.

A fore warning... 3,000 wats load will trip most circuit breakers (20 amp) and will definitly require a 10 gauge extension OR a dedicated electric line. If you can run each heater on a seperate circuit of your house, you should come out fine.

Link below is to the Littlegreehouse-com heating calculator. it gives heating load in BTU's , but there are several online unit conversion utilities to convert to watts.

Anthony D.

Here is a link that might be useful: Heating calculator

a 6x6x7 GH can easily be heated with a single, 1,500 watter ceramic heater..... IF.... it's insulated well!

If you could insulate it with something, i.e. bubblewrap or some of that solar pool cover stuff (very inexpensive) then you should be able to heat it with no problem and efficiently.

Our GH is approx. 11x11x11. It's well insulated this year and during the day, when there's sun, the heater doesn't run much or at all.

At night, it will kick in, but later on in the evening. Only during REALLY COLD SNAPS, will the 2nd heater kick in, but not very often this year, due to good insulation, water barrels/bottles and a circulating fan to move the air around.

I use a single 1500 watt heater in my 6' X 8' HFGH and have no problem keeping it warm enough. I have it hooked up to a thermostat that is set at 60. The coldest night we had so far was 3 degrees. The greenhouse only got down to 57.

I have the greenhouse insulated well and have a solar pool cover on it, which I think makes a huge difference. I also have a lot of containers of water in it.

If the 1500 watt heater is on continuously for 12 hours each night that costs you 1500 x 12 = 18,000 watt-hours of energy. Divide by 1000 to get 18 kilowatt-hours. Look on your electric bill to determine how many $ per kilowatt-hour you are charged and multiply that by the 18. So if you pay 14 cents/kwh then it would be .14 x 18 = $2.52 per night.

It would cost this much on a cold and windy night, but as the weather gets warmer the thermostat will turn the heater on for a much shorter time. Actual time the heater is on depends a lot on insulation at night as well as outside temperature and wind.

Bob B.

.... and on what you have inside the structure to buffer the temps. I.e. water barrels, large rocks (water's better) or even a pond.

Also, a GOOD circulating fan really helps I find.

No longer easy to find, but if you can get your hands on a 15" ro 18" oscillating fan that has one of those efficient motors, that only use 25 Watts on full, then you'll save $$$ as well.

If you're heating with an electric heater the efficiency of the fan is irrelevant - it will just offset the heater run time.

No, I'm not talking about the heater's fan. I'm talking about a fan that circulates the air to keep the heat more even throughout the GH. Plus, in our case anyway, we use several fans throughout the house during the winter (ie. humidifiers, circulators). So for us, every watt counts.

In our case, we use the ceiling fan, which runs 24/7. So, yes, I do want it to draw as little power as possible.

What can I say? I'm always calculating wattage. I guess that's due to the power backup system that we have. It's taught me to be aware of every watt used. :)

So was I. If you are heating your greenhouse nearly every day with electricity, then who cares about wasting power in the fan?

If you were heating with sunlight, or perhaps even gas, the energy consumption of the fan is significant. And bigger fans are better.

Are there any issues with a 1500 watt ceramic heater causing fires in the Flowerhouse Springhouse Portable Greenhouses? How far do they need to be from the walls? If the windows are closed at night and you insulate it with bubble wrap, does this make them more flammable?

I'm trying to be safe here! I am growing mainly peppers, tomatoes, lettuce, cole crops, and some basic flowers. Is it OK to set a heater at a minimum of 40 degrees at night to stop frost? Obviously you can see I want to minimize costs, but free up some room in my basement under gro lights!

Chris

Chris

Chris, last year I heated my little FlowerHouse Starterhouse with a little space heater that had a thermostat set to 55 degrees, but I didn't start until April.

This year I have a 6x8 WeatherGuard, which is similar material, and I'm heating with the same little heater. But again I waited until the start of April. Winter, including March, is just too friggin cold here to heat any GH any earlier, IMHO.

Not sure of the cost as my wife pay the bills, but I've not heard any complaints. I only run the heater when temps are forecast to be Tomatoes won't grow, I've read, if temps dip below 50 so I'd shoot to keep it 50 minimum.

I live in zone 6b and have a Juliana 8.3 hobby greenhouse. This time of year, if the forecast calls for temps. in the low 30's I use a ceramic heater. The brand name is Mr. Heater and it's both radiant and convection and is very economical to run. I use a standard propane tank used for grills.

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Here's a link to their site.

Paul,

Everytime I see that beautiful greenhouse, I'm green with envy. :) Just gorgeous set-up. I could get used to that real quickly.

Chris

How do you regulate the heat on the Buddy heater? There's only a "high" and "low" setting. Do you leave it on at a particular setting all night?