Most cost effective heating for shed and stove.

[David]

Following on from a couple of recent threads, and using as a reference.

John Runn said "If you fitted heatpump aircon instead, then it would be a third to a quarter of the price for normal resistive heating."

That would give an electricity cost of about (15.4/3) 5.1 pence per kWh. Possibly down to under 4p per kWh if the better estimate was met.

This compares to 7.1 pence per kWh for wood bought by the ton. Smokeless fuel is 6.3 pence per kWh when bought by the ton.

This makes using a wood burner in the shed a pure vanity project.

Propane bottle and radiant heater comes in at 15.6 pence per kWh so that is more expensive than normal electricity.

So on pure cost effectiveness on fuel use the air source heat pump seems to win hands down.

It feels wrong to just have aircon in the shed because it is cheap to run; I don't think I have ever been too hot because the insulated roof keeps most of the sun away, the shed is shaded, and probably only needs heating for less than half the year.

The kits linked to by Dennis seem to cost about £600. I would be saving, say 10 pence per kWh (easier calculation) for electricity against normal fan/radiant heating. So to get my money back I would have to heat the shed for approximately (600 * 10) 6,000 kWhours.

{note - screw up in first run of the calculations. Forgot to use wattage of heater.}

Which I think is not far off 10 hours a day for 2 years at 1 kWh or 5 hours per day of a 2kW fan heater.

Note that in the previous thread the calculation came out at needing 5kW of heat to keep the shed at 21C when it was freezing outside. However that was an extreme target as most times it wouldn't be at 21C nor would it be freezing outside.

If this is correct then I need to work out how many 5 hour days I am likely to spend in there.

If I were to spend 3 days a week over 6 months of the year, and only need heating for 3 months of the year, then I would need heating for (365/4) * (3/7) days per year. I work that out at 39 days a year.

Getting too late at night now, but if I am correct so far in my tortuous working pay back would be (2 years) * (365/39) = 18.7 years.

So it looks as though an air source heat pump doesn't cost in for the shed unless I am relegated to their for the rest of my active life and then some. Or unless my calculations are well adrift.

Since it is already established that the stove is more expensive to run than the heat pump and the installation of the chimney may be more expensive than installing a heat pump then the wood burning stove would be purely a vanity project.

Shame in some ways as having an air conditioned shed would be a definite one up over the neighbours :-)

It does make the installation of air conditioning in the house look quite attractive, though. Purely for cooling in the summer, though,

Cheers

Dave R

[spuorgelgoog]

If the house and shed are close enough together could you use one outside unit and two inside units, one in the shed for winter warmth and the other in the house for summer cooling?

Or one of the type that works with an inside unit and 2 four-inch vents through the wall, and move it from house to shed in autumn and spring?

Also if you can run your aircon off solar electricity that may change the economics.

Owain

[John Rumm]

That does depend a bit on what you do in the shed... if its used for woodworking any you have ready stream of wood offcuts, then that may change things.

(same would apply if its a "man cave" and what you really want is nice real fire to put your feet up in front of!)

FWIW, I heat most of my outbuildings using thermostatically controlled fan heaters. However most of the time they are just ensuring that the temp stays above the dew point to stop stuff getting damp or rusting. They are also insulated to one degree or another. I won't need them to be at a comfortable temperature most days - so low installation cost and ease of install / use is the winner for my use pattern.

It makes sense for frequent use spaces. Something like the split unit heat pump that Richard installed in his office outbuilding:

makes lots of sense, since its in use most days, and will need cooling and heating depending on the time of year.

[harry]

Solid fuel stoves are notoriously inefficient. Traditional ones may be only 10% efficient. Plus all the labour needed. They are only worthwhile if you can get free wood.

[Brian Gaff]

Of course anything that stays in the shed, say of an electronic type or machinery may not respond well to being allowed to cool down and heat up over such a large temperature range, so some background heating/cooling for the sake of equipment might need to be factored in as well. Brian

[fred]

ly 10% efficient. Plus all the labour needed.

lots of free wood around after recent storms

[Robin]

Not much freely available in inner London to feed the many wood burners fitted when Victorian (and earlier) houses are renovated. (I sometimes wonder if there's an untapped market for faux wood burners that *don't* have lamps and electric heaters, but do have capacity for genuine ash.)

[Iggy]

replying to David, Iggy wrote: Well, I can't disagree AT ALL with heating AND wonderful-marvelous-is-the-bees-knees cooling. However, for a nice, cheap, never needs a Technician heating solution of somewhat small spaces, is a Halogen light bulb heater. You can do like this "Low watt space heater EASY BUILD"

or you can just screw bulbs into a bunch of sockets on a board and make it your top central lighting. You'd just put a tiny fan next to the bulb-field to circulate the shed's air for a very reasonable 500 to 600-watts. In other words, turn the shed into a giant Easy Bake Oven.

[bin]

I must be missing something. A regular resistance heater converts all the energy into heat, this converts the energy into heat and light. Unless you need the light, how is a heater based on light bulbs better than a regular resistance heater?

[David]

Nice thought, but shed is down the bottom of the garden.

Cheers

Dave R

[spuorgelgoog]

Perhaps you could get domestic permission to erect a shed about half-way, and then sneakily fill in the gaps?

Owain

[David]

Some years back now, but this is the Mother Of All Sheds (threads passim) and that would involve covering the entire back garden in shed.

Fair enough, you might say, but this would almost certainly give the planning department indigestion.

We also have other plans for the rest of the garden :-)

Cheers

Dave R

[Iggy]

replying to bin, Iggy wrote: Rod Speed's got it. Actually, the problem with a Resistance Heater is that it's much more wattage and has a, comparatively, miniscule hot spot with no buffer or heat exchanger. Even at 1500-watts a Resistance Heater Is only effective for close proximity and takes very long to heat up a space's items (heat soak), due to its lack of Volume Heat.

If he does something like the video with glass instead of ceramic, he gets both light and heat by creating a heat exchanger...where mostly just the outside surface heat is blown off but not much of the heat source is depleted, creating a constant provision of steady heat. If he needs to adjust to lower and higher demands, he just removes or re-installs bulbs (or unscrews partially, if he opts for that convenience).

[tabbypurr]

???

[Iggy]

replying to tabbypurr, Iggy wrote: You'll have to be a little more specific than that.

[John Rumm]

and none of us want to catch it...

Not necessarily true. Storage heaters, immersion heaters etc all have storage buffers.

I get the impression you don't understand what a "resistance heater" is, since none of that makes any sense.

For clarity, a resistance heater is basically *any* type of electric heater (radiator, radiant element, fan heater, storage heater, inline water heater, immersion heater etc).

The term really only differentiates from heat pump systems that use electricity to move exiting heat from one place to another rather than produce it in the first place.

Perhaps we can recommend a good physics book for you?

[bin]

I think we'll just agree to differ on that. Unless the light is needed a fan heater will be more efficient. (I don't know why you made the "Rod Speed" comment.)

[Iggy]

replying to John Rumm, Iggy wrote: Oh thank you Lord Heatwiser and sidekick Bin, I had no idea how brilliant you are. I feel so graced by your omniscience of the world, I now realize I'm in. I see the error of my ways in providing a life-long simple alternative. I should've absolutely sat in the corner as the Masters parted the sea of ignorance with their magnificent 1500, 3000, 4000 and more-more-more watts of high expense frontal pleasure and backend sublime agony. Please forgive me, my eyes have been opened and the illumination of such pure brilliance has freed my soul from the eternal darkness.

[Roger Hayter]

Good. Now you just need to get away from homeownershub.com and you can start rehab.

[Steve Walker]

A conventional heater has to heat the air and heat is continuously being lost to the environment. Spotlights (or better, the equivalent, purely infra-red heaters) give you radiant heat directly onto your skin. You can feel warm with them in a much cooler room and so save energy. They are often used in factories, loading bays, etc.

SteveW