Cost benefit analysis - coal vs logs.

[Doodlebug]

I’ve been searching and am surprised not to find anything on this topic. 
 

Has anyone done a proper cost analysis of coal vs wood? It strikes me that coal is significantly cheaper but that seems to be counter intuitive. 
 

For instance if I burn 5kg of coal a day and let’s say £20 a bag to make the numbers nice. That’s £4 a day.
 

Meanwhile a  bag of logs seems to be around £8 and probably won’t last more than a day and a half if that’s the only fuel source. 
 

Does anyone have any thoughts better than my rough calculations in my head? I’d much prefer to only use wood but I imagine it doesn’t work cost wise. 
 

Any cheap sources of kiln dried logs? 
 

Thanks! 

[LadyG]

I buy a mix for the reason that my stove does not start well with coal and firelighters.

I use

Matches

firelighters

Kndling

Split logs, Silver birch preferred

Ovals, at £16.50 for 25kg

Six excell

Eight logs

Three kindling 

£150

Firelighters £5.00 

£20 to £30 per week

Logs don't stay in overnight. 

Hardwood logs kiln dried are about £8,5 per net.

I have a delivery from those who deliver coal logs and kindling.

Cheapest logs are those you forage, but need to be cut and dried.

 

 

 

 

Edited March 28, 2024 by LadyG

[Alan de Enfield]

You need approximately twice as much wood as coal to generate the same heat.

 

 

Seasoned dry wood = 4.2Wh/gram

Coal - Anthracite (which is the basis for most smokeless fuels) = 8.6Wh/gram.

 

The volume of wood is many, many times that of coal for the same energy so you need a huge anount of (dry) storage space

Edited March 28, 2024 by Alan de Enfield

[Doodlebug]

Just now, Alan de Enfield said:

You need approximately twice as much wood as coal to generate the same heat.

 

 

Seasoned dry wood = 4.2Wh/gram

Coal - Anthracite (which is the basis for most smokeless fuels) = 8.6Wh/gram.

 

The volume of coal is many, many times that of coal for the same energy so you need a huge anount of (dry) storage space

Interesting. So what do you think the impact on price is for this? 
 

I know the cost per Kg or coal but not so much with logs. 

[Alan de Enfield]

Just now, Doodlebug said:

Interesting. So what do you think the impact on price is for this? 
 

I know the cost per Kg or coal but not so much with logs. 

 

 

It is difficult as logs tend to be sold by volume (or per bag / net) Ask a supplier for a typical 'bag' weight of logs.

 

Find the weight of a bag of logs and work out the price per gram / Kg etc.

Do the same for your solid fuel of choice.

 

If the cost of the solid fuel per gram / Kg is less than twice that of the wood, coal is the cheapest form per Kw

[magnetman]

A lot of this depends on whether you want the fire to stay in overnight. 

 

I let the fire go out. Always nice to have a cold start and do some problem solving so wood is the answer. 

 

Having said that I also have a good supply of free wood which helps ! 

 

In the past when I have needed full time heating due to having other occupiers aboard the Boat in the form of a woman and children I used less smoke coal as I think it is cheaper and it will stay in. 

 

 

[booke23]

I've considered this question myself in recent times and it is certainly cheaper to burn smokeless coal per kw/h of output. As mentioned coal has a much higher output per kg. 

 

The government have done some heat output tests and the results indicate kiln dried wood is about 2.5 times more expensive per kw/h compared to smokeless coal. The only way it's cheaper is if you can get free wood. 

 

[ditchcrawler]

I have been trying these at home I pay £3 for 10Kg. I find them very controllable from just a smoulder to flaring away, a lot cheaper than logs.  I thing they would work well in a small stove. My stove is quite large so I mix them in with soft wood 

[Doodlebug]

1 minute ago, ditchcrawler said:

I have been trying these at home I pay £3 for 10Kg. I find them very controllable from just a smoulder to flaring away, a lot cheaper than logs.  I thing they would work well in a small stove. My stove is quite large so I mix them in with soft wood 

What are they called? They look like giant wood pellets 

[magnetman]

Wood briquettes. 

 

These need to be stored dry. If you get them damp they turn into porrridge. 

 

Brilliant for burning and often very cheap depending on the season. I found some of these which were waste from a window frame production company and they only wanted 50p for 20kg. In the middle of the summer. Better than landfilling the sawdust. 

 

 

 

A lot of wood product companies have bought the briquetting machines. I imagine there was some fairly well thought out marketing but I'm unsure as to whether it proved economically sensible. When I bought some of these they were offering to cart a van load to the Boat for a good price. Trouble is they turn into porridge (inedible but exactly the same consistency) at any hint of moisture. They really do. Would be great dehumidifiers or bilge soaker uppers. 

 

 

Just a random example. There will be others. 

[tree monkey]

Unless you can source your logs for free or buy unprocessed bulk timber coal is cheaper with the advantage of a lot less bulk/volume to store.

 

When I say bulk I'm talking 20ton not a transit load and then you have the problem of seasoning and storage, plus of course processing.

 

The additional problem with wood is the quality and species as well a tonne of well seasoned Oak is a thing of beauty but get delivered a bag of soggy willow and you need extra jumpers, whilst excel is basically always excel

 

So in my opinion coal unless you can get free timber but even then have some coal as a back up

[ditchcrawler]

1 hour ago, magnetman said:

Wood briquettes. 

 

These need to be stored dry. If you get them damp they turn into porrridge. 

 

Brilliant for burning and often very cheap depending on the season. I found some of these which were waste from a window frame production company and they only wanted 50p for 20kg. In the middle of the summer. Better than landfilling the sawdust. 

 

 

 

A lot of wood product companies have bought the briquetting machines. I imagine there was some fairly well thought out marketing but I'm unsure as to whether it proved economically sensible. When I bought some of these they were offering to cart a van load to the Boat for a good price. Trouble is they turn into porridge (inedible but exactly the same consistency) at any hint of moisture. They really do. Would be great dehumidifiers or bilge soaker uppers. 

 

 

Just a random example. There will be others. 

It was you who seeded the idea on a thread about getting wood and the fact there are lots of outlets near canals . I am using them at home so stacked in the garage 

[magnetman]

12 minutes ago, tree monkey said:

Unless you can source your logs for free or buy unprocessed bulk timber coal is cheaper with the advantage of a lot less bulk/volume to store.

 

When I say bulk I'm talking 20ton not a transit load and then you have the problem of seasoning and storage, plus of course processing.

 

The additional problem with wood is the quality and species as well a tonne of well seasoned Oak is a thing of beauty but get delivered a bag of soggy willow and you need extra jumpers, whilst excel is basically always excel

 

So in my opinion coal unless you can get free timber but even then have some coal as a back up

 

I like having a lot of dead hawthorn available. Oh yes and ash ! 

[MtB]

1 hour ago, booke23 said:

I've considered this question myself in recent times and it is certainly cheaper to burn smokeless coal per kw/h of output. As mentioned coal has a much higher output per kg. 

 

The government have done some heat output tests and the results indicate kiln dried wood is about 2.5 times more expensive per kw/h compared to smokeless coal. The only way it's cheaper is if you can get free wood. 

 

 

 

Interesting bar chart, thank you.

 

I did my own cost comparison calcs back during Covid and I spent quite a lot of time researching the cost per kWh in the various fuels. Wood was the most difficult to pin down. I can't remember my methodology for the wood but it was based on the price of a cubic metre of kiln-dried oak, including delivery to me and the cost I came up with was 7p per kWh. Solid fuel was 8p per kWh. 

 

Quite a difference from the bar chart above but mine was for the total calorific value of the fuel, not the 'useful' calorific value which strikes me as a matter of opinion! 

[Sir Percy]

I've just spent a hundred quid on these bags of hardwood logs

https://www.fireandflame.co.uk/product/fireflame-4x-hardwood-logs-copy/

which were being cleared out at £4 a bag (normally £8) from the local Sainsbury's. You may want to look around at your own; I've never seen this particular seasonal knockdown before. Note: not online.

I don't know if you can really compare coal and wood on a therm/£ basis. The wood burns hotter and faster than coal. I'll hold off using the wood until the longer, colder winter nights.

As for wood briquettes, I've still got the recycled cat litter idea in the back of my mind.

 

 

 

 

Edited March 28, 2024 by Sir Percy

[LadyG]

Deleted

Edited March 29, 2024 by LadyG

[cuthound]

22 hours ago, LadyG said:

I buy a mix for the reason that my stove does not start well with coal and firelighters.

I use

Matches

firelighters

Kndling

Split logs, Silver birch preferred

Ovals, at £16.50 for 25kg

Six excell

Eight logs

Three kindling 

£150

Firelighters £5.00 

£20 to £30 per week

Logs don't stay in overnight. 

Hardwood logs kiln dried are about £8,5 per net.

I have a delivery from those who deliver coal logs and kindling.

Cheapest logs are those you forage, but need to be cut and dried.

 

 

 

 

 

And a partridge in a pear tree!

 

Surely its not Christmas already

 

[LadyG]

It is vital to buy kiln dried hardwood logs, as i know to my cost. Ran out today so bought a bag from local building supplies.

They could not be wetter if they'd been floating in Timber Ponds for a week.

They insist on me returning them, 

Its actually illegal to sell wood unless its 20% moisture content, and they have a yard full of the stuff!

Edited March 29, 2024 by LadyG

[Jon57]

2 minutes ago, LadyG said:

It is vital to buy kiln dried hardwood logs, as i know to my cost. Ran out today so bought a bag from local building supplies.

They could not be wetter if they'd been floating in Timber Ponds for a week.

They insist on me returning them, 

Its actually illegal to sell wood unless its 20% moisture content, and they have a yard full of the stuff!

Hope you get your money back. 💰😁

[Alan de Enfield]

1 hour ago, LadyG said:

Its actually illegal to sell wood unless its 20% moisture content,

 

So you cannot legally sell / buy wood or logs at 19% or 21% moisture content ?

[David Mack]

50 minutes ago, Alan de Enfield said:

 

So you cannot legally sell / buy wood or logs at 19% or 21% moisture content ?

You can only supply or sell wood fuel in volumes of less than 2 cubic metres if it is certified as ‘Ready to Burn’. This confirms it has a moisture content of 20% or less.

The Ready to Burn certification scheme applies to:

• firewood in single retail bags
• firewood supplied as a bulk delivery in loose volumes of less than 2 cubic metres
• wood briquettes in single retail bags
• wood briquettes supplied as a bulk delivery in loose volumes of less than 2 cubic metres

https://www.gov.uk/guidance/selling-wood-for-domestic-use-in-england

[Alan de Enfield]

3 minutes ago, David Mack said:

You can only supply or sell wood fuel in volumes of less than 2 cubic metres if it is certified as ‘Ready to Burn’. This confirms it has a moisture content of 20% or less.

The Ready to Burn certification scheme applies to:

• firewood in single retail bags
• firewood supplied as a bulk delivery in loose volumes of less than 2 cubic metres
• wood briquettes in single retail bags
• wood briquettes supplied as a bulk delivery in loose volumes of less than 2 cubic metres

https://www.gov.uk/guidance/selling-wood-for-domestic-use-in-england

 

Yes I know all that but Lady G seems to think it can only be sold when it has 20%. (not 20% or less)

[Paul C]

46 minutes ago, Alan de Enfield said:

 

Yes I know all that but Lady G seems to think it can only be sold when it has 20%. (not 20% or less)

 

Common sense would have interpreted it as meaning 20% or less.

[MtB]

49 minutes ago, Alan de Enfield said:

 

Yes I know all that but Lady G seems to think it can only be sold when it has 20%. (not 20% or less)

 

A website you'll probably be fascinated with Alan!

 

nit-pickers-R-us.com

[Alan de Enfield]

4 minutes ago, MtB said:

 

A website you'll probably be fascinated with Alan!

 

nit-pickers-R-us.com

 

Would you be kind enough to provide a link as it doesn't seem to exist as you have written it.

 

"Computer says no - MtB may have made a typo"