Heating Conservatory & Garden Office. Mix Calor Gas & Electric?

andre_xs

Dear All,
we have a small conservatory (~3m x 3m) which we use as dining room (the space of the house doesn't allow to eat in the house) and also a shed converted to a home office during Covid. Both are at the moment heated just with portable electric heaters, which of course was already very expensive last winter, and will be expensive again. Thus, we're looking at some cheaper options to heat.

I was wondering whether the addition of calor gas bottles with a portable heater might be a solution? In particular to heat the rooms up in the beginning when they are cold. I'm not sure how much the gas heaters can be regulated down, so possibly once the rooms are warm, it's cheaper to turn off the gas heater and just keep the temperature with portable electric heaters (we have e.g. a portable electric oil radiator)?

My understanding is that the bigger 47kg bottles are much cheaper than the smaller e.g. 15kg bottles. However, I wasn't able to find much about how much heat they produce compared to an electric heater. I've come across one site which said ~15p/kwh, but I don't know how old the site is and whether this is comparable to a kwh-price of an electric heater. If so, it would be much cheaper!

The cheapest/most flexible solution then probably would be using a 47kg propane bottle and a heater of this kind: 
https://encrypted-tbn2.gstatic.com/shopping?q=tbn:ANd9GcRRzcM0b6om5YNMFo_nrbvuuJ9qYE9e6TCIJ2q1ePhgfVGxT7r_jGZDJCG75iSPE3DqH68EAoilIz1WVWxYmB_neUI_15ZpNQ&usqp=CAY

Any further suggestions, thoughts, etc would be greatly appreciated. I'm not fixed on this, it was only a spontaneous idea and I'm open to suggestions and open to learn that this might be a bad idea?

Best wishes,

Andre

QrizB

You're not meant to use propane bottles indoors for safety reasons. (See eg. para 1.1 here, this page from Calor and this page from FloGas).

If you want to use a LPG space heater, you should really be looking at one like this (other suppliers are available) used with butane.

andre_xs

Thanks a lot. I also realised in the meantime that the 47kg bottles have a gross weight of roughly around 100kg? This would make it a bit impractical

Ok, so the question remains: Would such LPG space heater (using the 15kg butane bottles) be a sensible addition? Or would it save so little that the initial investment costs are not worth it?

Best wishes,

Andre

andre_xs

I just had a look on the Calor homepage:
15kg butane refill is specified with £50.

On their homepage, this bottle has the following specs:

Rec. offtake (approx)	9.9Kw

I guess this doesn't mean that you get roughly 9.9 kw heating power out of it? So the question is, roughly how much kw/h equivalent would the 15kg bottle be when compared with an electric heater?

QrizB

15kg of butane contains about 110kWh of energy. If a refill costs £50, that's 45p per kWh - slightly cheaper than the new capped electricity price.

The 9.9kW number is the maximum recommend rate that you draw gas from the bottle. In practice a portable heater will use less than half that amount.

andre_xs

Thanks a lot, very helpful.

Thus, given that there's an initial investment of £100 for a space heater, this would mean that it would have paid for itself after £100/.07 = ~1400 kwh (assuming a saving of 7p per kwh).

Assuming that heaters run on the high 2000W setting, the break even would be after ~700 hours.

For the conservatory, which we use only max 2 hours per day for dinner, this would be after 350 days, or roughly 2 years (no heating during summer).

For the garden office, assuming 8 hours per day at 1000W, the break even would be after 1400/8 = 175 days, so roughly 1.5 years.

So in the big picture, it probably won't make a huge difference (around £100-£200 savings per year).

I'll check the local prices for refills, that may change the picture somewhat...