Best small greenhouse heating?

[SaraJean]

Well, it looks like we might actually get a winter here this year
I have a very small 55.5” (L) x 56.3“(W) x 76.8“(H) pop up greenhouse that is new to me this year. My collection has finally outgrown the bathroom window and the mini 1.5’x 2’ greenhouse that was much simpler to heat. My nighttime temps are going to be in the low 40’s and mid 30’s this week and I am looking for the most efficient/easiest solution to keep it in the 60’s. A plug in space heater is probably out due to having to run an extension cord over to the greenhouse area.
Any thoughts?

[Selmo]

I think that an extension cord and space heater is going to be the simplest and be temporary.

[fooferdoggie]

heaters on extension cords are a no no. they just draw too much power. a propane or kerosene heater may be better.

[Dollythehun]

Small greenhouse. Vents? Alternative fuels have fumes even if ever so slightly.

[fooferdoggie]

something liek this may work https://www.walmart.com/ip/Dyna-Glo-...&wl13=&veh=sem

[Ray]

Originally Posted by fooferdoggie

heaters on extension cords are a no no. they just draw too much power. a propane or kerosene heater may be better.

It's all a matter of matching the current needed, the distance, and the wire size.

A 1500 watt, 110V heater draws a bit below 15 amps. A 10-gauge cord is good for that over 100 feet of distance without a safety hazard. If you can halve that distance, 12 gauge is sufficient.

[dounoharm]

you can always bake a few bricks in aluminum foil....about 4 should do it if you put them in just before bedtime....keep them stacked together and they hold the heat longer....

a few nights at 40 or even lower wont hurt them....I have my temp set to stay above 55, but I have babies....with just a few plants, bring them in!

we use nat gas as it is cheap out here in texas, but last winter, on the very coldest week, the gas pipeline froze up. my honey was furious, as he had worked in the gas fields and said that they were lazy and allowed the condensate to build up and freeze....BUT, we had no NO heat to back up! I had just finished my new gh last fall, and so I put down my trusty electric seedling mat...5 ft by 18 inches...and I put all the plants on the floor of the gh, with the most tender on the mat and the others piled around them, stacked on them and prayed....it was a bad time financially, so we could not just run out and buy heaters....

in the house, I had one foot warmer electric pad...all my kitties and myself stayed on it for 3 days! 3 DAYS!!! finally they cleared the pipeline, and paul connected us back himself, as we just couldn't wait for them to go house to house and hook people back....

I lost my blooms on a couple plants, but everything lived! amazing! orchids can take a lot of abuse, huh? this year, we bought an electric heater for backup....

[estación seca]

Yes, an electric space heater with the proper extension cord. Make sure the plug connects inside the structure.

That small space, and your relatively mild temperatures, mean you don't need a big heater. Go to a real hardware store (not Home Depot, not Lowe's, whose employees might not know anything about electricity) and tell them what you want to do. They will be able to help you pick an inexpensive heater and a heavy-duty extension cord.

Be sure nothing else is on that circuit. If you live in an old house the circuits might not be able to handle any more load. I can't use a space heater in my sunroom and turn on the overhead light in my library. They are on the same circuit.

The brick trick dounoharm mentioned is good. Water works well, too. Put as much warm water, in jugs or kettles, as you can possible fit under the plant benches. This, even without the heater, would make a huge difference.

[Roberta]

Originally Posted by SaraJean

Well, it looks like we might actually get a winter here this year
I have a very small 55.5” (L) x 56.3“(W) x 76.8“(H) pop up greenhouse that is new to me this year. My collection has finally outgrown the bathroom window and the mini 1.5’x 2’ greenhouse that was much simpler to heat. My nighttime temps are going to be in the low 40’s and mid 30’s this week and I am looking for the most efficient/easiest solution to keep it in the 60’s. A plug in space heater is probably out due to having to run an extension cord over to the greenhouse area.
Any thoughts?

If you can run power to it safely, a 1500 watt heater is sufficient (with those temps, without a lot to spare in my experience) Advantage of those is that you can set the heat level on a thermostat.

However, here's a nice little propane heater https://www.walmart.com/ip/Mr-Heater...eater/16622306 (I have one, and used it until I got a built in heater after I found that the electric heater was not adequate in my 8' x 12' GH when temps got down into the 30's F . It is rated for indoor use if you use it with a 1 lb cylinder (like for a propane torch), that will give you about 4 hours on low setting. However, I recommend that you get the extension hose and hook it to a 20 lb tank (like for a barbecue), good for about 90 hours. The heater (either model) is safe inside the GH without venting, it's the big tank that needs to be outside. (I think both were designed to be used in RV's)

This one might actually be sufficient, but I don't think you can get the hose for the larger tank, so you have to use it with the 1 lb cylinder.
https://www.walmart.com/ip/Mr-Heater...eater/20450314



Both of these models, and the extension hose, are also available on Amazon...(I just checked) Walmart shows "out of stock"

[stonedragonfarms]

I'll second both the electric heat with a heavy-duty extension cord route (which is what I used in my 10x12' gh in Eugene, OR); just put it on it's own circuit, or one that is not used in the evening (mine was shared with the lights in the barn, which, 99% of the time, were only used during the daylight hours); but I'll also second Roberta's first propane heater--I used a similar one in my 18x20' gh in northern MI as my emergency back-up heater, paired with a 20 gallon propane tank. On the lowest setting, it gave me about 60 hours of burn time; though I grew mostly cold stuff (about 99% cymbidiums), so as long as the gh was in the 38-40F range as a low, I was happy...
Adam