How much does it cost to heat a greenhouse?

Hi, part P is a building regulation. It came out in 2005 with the idea to save lives by stopping people doing things that are dangerous.

That aside, you do have a solution that I will come to shortly.
You can't run an extension lead to a green house as the cable is just not up to the job. Normal extension lead flex is not designed to take all sorts of weather. Also you can not fix it to a temporary structure such as a fence. The other thing to be considered is Voltage drop. The long and short of that is the longer the cable run (From house to green house in this case) the more voltage you will loose. (stuff wont work as well as it should) The way round it is to install a bigger cable, but you can't get a bigger (cable) extension lead so what can you do?

An electrician will not really want to dig a trench to put in a cable, but you can, that way you save a lot of money in labour. You can consult an electrical see what size cable he works out, buy it and put it in a trench yourself. The cable is called steel wire armoured.

Now the bad news.

For my example lets say you need to heat your green house and you use 1,000 watts every hour. (Your average fan heater is 3kw) But lets just say 1,000 watts.

Electricity is one of the most expensive ways to heat anything, I just did a quick google and average price is around 11p / kwH

Lets say you need the heater on 18 hours / day
18 x 11 = 198

Average month = 30 days

30 x 198 = 5,940

You said you will want it for 5 months

5 x 5,940 = 29,700

297,00 pence is £297.00

So to heat your green house by 1kw for 18 hours / day for 5 months will cost you £297.00 (and if its 3 kw that would be nearly £1k

Also as Kristen pointed out, forget a wind turbine, unless they are in clear air space they are too unreliable.

 

Aesculus this is all too much for me. Surely it depends on how cold the winter is?

Basically you heat just a small area over winter, that you section off for the more delicate plants.
Others will probably take lower temps.
I run a propagator, any thing from 20C up wards, a slightly warmer section min 6C and a frost free section.
It wont cost the earth if you are careful and get good thermostats, dont rely on the ones attached to heaters.

Some extra insulation in winter helps a lot but I never get round to doing it, a bit lazy I guess.

 

They've been sold snake oil :( The days are shorter, the sun is lower in the sky, the "sun power" is a tenth of what you get in the Summer, it ain't enough to give you a return on your money in the Winter. The reason they are laughing all the way to the bank is the FIT rebate CASH they got for being an early adopter.

When you have got kWh figures from them that prove that they are making good money in the Winter let me know until then I'm happy with "Sun Power" in Winter = Summer / 10

 

There's 267 kw/H in a 19 kg Propane gas cylinder that I buy for £24.95, making it just over 9p/kwH, but I have to search around to get it at that price and many people pay approaching £40 for their 19kg cyclinders making it over 14p/kwH. Smaller cylinders work out much more expensive per kg/kwH. But if you have Economy 7 with half price overnight elecricity, it's cleary the cheapest per kwH.

 

The good thing with "Sun Power" is its free and it`ll always be free, a 50ft x 50ft garden gets hit with 267kw every hour...thats what you call cheap

 

Its not what I call free! The equipment to convert Sun to Electricity is expensive (relative to just carrying on burning oil :( ).

But I agree with you in the sense that my Vegetables do an excellent job of converting sunlight into stuff that is great to eat!

The average Insolation levels (kWh/sq.m/day) are:

London Jul=4.74 Dec=0.52
Edinburgh Jun=4.34 Dec=0.32

(I've used average sunshine hours to convert kWH to kW - e.g. 203 sunshine hours in average July in London, only 48 in December; Edinburgh = 179 / 40)

so in your 50' x 50' garden, in London, you'll get 1100 kWh per day (167 kW) in Summer and 120 kWh (77 kW) in Winter

(and for Scotland 1000 kWh (167 kW) in Summer and 74 kWh (57kW) in Winter)

So by my calculation its 10x more total energy in Summer, and twice the "power" when its shining

(which I think makes sense as Sun at e.g. 30 degrees above horizon is spread over twice the area as sun that is directly overhead - Cosine rule )

 

I`m not advocating the notion of converting it with expensive pv panels :WINK1: why would anyone want to pay to convert the sun`s energy into electricity if they plan to use it for heating?
The sun reaches 14 degrees azimuth here at noon on the winter solstice, sloping panels would be almost useless at intercepting any direct sun, they`d do better 15 degrees off vertical

 

Indeed, quite agree. My [solar hot water] panels are at a sharp angle to try catch the Spring/Autumn sun. They produce hot water easily enough in Summer, so my aim was to set them optimally so that we get hot water Spring / Autumn too, and thus only use the boiler for a short season each year.

My point above was that the strength of Winter sun is pathetic compared to Summer, and thus for anyone thinking of using it for any form of Winter fuel they would need massive numbers of panels - which will be expensive.

When the sun is out my greenhouse gets nice and toasty in Winter sadly I still have to heat it on cold Spring nights though :(

 

Only picking up on this thread now (new member).

I have a greenhouse with primarily cacti and succulents.
Unless you specialise in the Brazilian species, you really do not need to heat it to 12*C.
For most species, half of that would do.

 

You can also decrease your heating cost by bubble wrapping inside your greenhouse. I have a Rion Greenhouse 8'x24' with 8.5 peak.

 

Hi CB, Blimey, do you need insulation for a greenhouse Florida!

 

I tried heating my greenhouse for my cactus & succulents but found that it made too much condensation, air was far too damp and some had fungus growing on them. Much easier to take them indoors.

Val

 

How are you heating your greenhouse?