Is burning wood cheaper than electricity?

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Is burning wood cheaper than electricity?

Postby FarmerJohn » Thu Jun 27, 2013 9:04 am

On another thread its been suggested that a wood burner heats a house cheaper than electricty.

For me wood is definitely cheaper right now because it is free from my own block and surrounding areas and I chop it up myself. Costs = chainsaw maintenance, fuel and lube and of course all the extra food that I have to eat when I am doing that hard yakka ;) However, I don't ever cut down good trees, and for every downed tree I use I plant at least three more. This is personal policy for me, so I should factor those costs - but I didn't here.

Here hard firewood is around $100 to $120 per cubic meter ready to burn, I don't know what that is in Kilos, I'll guess at 700 kilo. I can easily use 15kilo per day in the winter and 25kilo to get the house from freezing to warm - for those times when I arrive there after a few days out. Also I have to go and buy it and haul it back - so there is some diesel involved.

That's around 40 days heating so $2.50 per day.

Considering I try really hard to only use offpeak when I use the grid, $2.50 would buy me about 14kwh. Past experience tells me that is not enough for a day - however, I just got double pane glass installed everywhere now so that may change things - but it is too soon to tell - and in any case it would also reduce my wood requirements in direct proportion - but with a wood burner it can be hard to go below a certain heat output.

With electricity the way you use that power is going to be important in the comparison.

From my research, a modern heat pump driving a hydronics (water based) heating system either on a well insulated slab or with wall mounted radiators should be the best; however, I don't have that.

My system is a largish reverse cycle A/C and this is probably the next best way to burn electricity for heating (opinions on that welcome, but this is my conclusion so far).

Finally there is resistive heating. This is the least efficient - with one exception; it can be efficient if you need to just heat one room in a house differently to the rest and by using a little heater you can avoid needlessly heating zones that don't need it.

I love burning wood to heat our house, but there are another costs that only become really apparent over time. Every time you open the firebox ash comes in the room - you don't necessarily see it, but it makes more dust. Move vacuuming time! Additionally you have to budget for maintaining the wood stove - getting the flue clean etc. If you are a lazy fire-starter and use commercial products like fire-starting blocks or commercially produced kindling, then you need to add those costs on as well.
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Re: Is burning wood cheaper than electricity?

Postby Gordon-Loomberah » Thu Jun 27, 2013 9:22 am

FarmerJohn wrote:My system is a largish reverse cycle A/C and this is probably the next best way to burn electricity for heating (opinions on that welcome, but this is my conclusion so far).


Small inverter RCACs are better than large ones, since they always have a higher COP/EER.
2 X 2.5kW (output) units will use less energy than a single 5kW unit, for the same amount of heating.

I have read that this is due to the indoor units in split systems not scaling up in size as the outside unit does, but I remain to be convinced, since systems with multiple indoor units don't seem to be any better, for the ones I have looked up at least, the COPs are still low.
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Re: Is buring wood cheaper than electricity?

Postby bpratt » Thu Jun 27, 2013 7:29 pm

Burning wood over flicking on a A/C is too much hard work for my liking. :)

When you look at the overall cost of obtaining the timber and the manual work involved in it, even if you have acres of timber lying on the ground, A/C would still appear to be the cheapest way to warm your house up.
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Re: Is buring wood cheaper than electricity?

Postby jimbo » Thu Jun 27, 2013 9:53 pm

We have burnt around 5 cubic metres of wood already this year and there is plenty of cold weather left!!! We are paying between $80-100/m but should have a enough of our own next year!

Reverse cycle AC is very convenient but I find the heat terrible. Makes the room stuffy and humid and I would chose any kind of heating over it but I like the idea of a heat pump/hydronic system.
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Re: Is buring wood cheaper than electricity?

Postby Smurf1976 » Thu Jun 27, 2013 10:01 pm

Looking at my own situation, here are the figures.

Wood at $130 per tonne (delivered price, quantity measured on weighbridge) and electricity at 16.757 cents per kWh.

There's about 16.2 MJ in a kg of wood, and the heater I have is supposedly 61% efficient. So That works out at 2.75 kWh per kilo which works out at about 4.75 cents / kWh.

So an electric reverse cycle A/C would need to be at least 350% efficient to break even with wood. Given that the one I just had installed at my mother's place has an average heating COP of 4.1 it's clearly possible although the saving isn't huge.

There is also a point about price trends. Since the mid-1990's the price of wood has gone up 50% whilst the price of electricity has tripled and LPG has at least doubled.

Electric is a lot more convenient than wood however. Hence why I use the electric resistance heater quite often on weekday evenings when I just can't be bothered with the wood fire. I'm happy to use wood on the weekends, but it's not much fun getting home at 8pm then messing about lighting fires.

All up, I use about 3 tonnes of wood and 5000 kWh of electricity for heating the main part of the house each year. Plus around 200 kg of pellets to heat an infrequently used area downstairs. Heating is by far my largest energy use at home. It's been down as low as 6 degrees inside the house recently with the heating off, so it's a fairly big task to get that up to 22 degrees.
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Re: Is buring wood cheaper than electricity?

Postby davidg » Thu Jun 27, 2013 10:03 pm

I'm putting in hydronic in the farm house, once I start building it. fire will be one of the add heat to it systems.
It is rather hard to have that much electricity to heat water in the winter, in an off-grid system.
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Re: Is buring wood cheaper than electricity?

Postby bpratt » Thu Jun 27, 2013 10:50 pm

jimbo wrote:Reverse cycle AC is very convenient but I find the heat terrible. Makes the room stuffy and humid and I would chose any kind of heating over it but I like the idea of a heat pump/hydronic system.


I think there must be something wrong with your A/C if it's making your room more humid. ;)

Not everyone is going to like the heat from A/C as it can be too dry for some, it's all a personal preference.

I prefer A/C for the convenience factor. :)
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Re: Is buring wood cheaper than electricity?

Postby jimbo » Thu Jun 27, 2013 10:59 pm

I don't use my AC for heating, I'm just peaking from experience in my travels. How exactly is it a dry heat?
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Re: Is buring wood cheaper than electricity?

Postby Tracker » Fri Jun 28, 2013 6:48 am

jimbo wrote:I don't use my AC for heating, I'm just peaking from experience in my travels. How exactly is it a dry heat?

Well , more relevant, how can it be DAMP heat .. :(
Just being obvious, but the RAC can't add moisture, and so it can't cause any added dampness.
What it can do is to give the sensation of dryer heat.. :oops:

I don't mind RAC heat, unless it's too hot, and then the dryness stands out. The bride does not like RAC heat because it affects her sinuses and this is because of drying... that is obvious to her..

It's still an interesting phenomenon , as unlike the cooling process, which DOES remove moisture , heating does nothing to the air ingredients, other than heating it ALL...

someone with a clear understanding of how things work with moisture and temperature, might explain the not so obvious ..

I love a wood fire. They are actually entertaining.. Provided that someone else is cutting it up for you.. :idea:

As for the early suggestion about real cost, I can't see how comparing to off peak rates is valid.. you desire heating whenever it is cold, not when electricity is cheap... ;)
Now, if you had a heat bank that could be heated at OP rates and used on demand, then that would be different..

I had considered one of those ultrasonic water atomization devices, to satisfy the bride, but the fear would be that as the RH would rise, to give the sensation of 'moist heat' , you would have water running down the cold windows.
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Re: Is buring wood cheaper than electricity?

Postby jimbo » Fri Jun 28, 2013 8:32 am

I understand it can't add moisture and I probably chose my words wrong. Maybe I should say the rooms feel 'stuffy'.

Also when calculating the cost you have to take into consideration the operating temp (outside) versus the temp at which the COP was calculated. There may be quite a difference in efficiencies
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