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Biomass boiler vs heat pump : The fight is on!

Posted by Tasha Kosviner on 25 March 2015 at 10:55 am

Domestic biomass installations now outstrip the entire heat pump industry in the UK. But is biomass always better? When might you choose a heat pump instead? We’ve pitted these two titans of the domestic renewable heating world against each other and here’s the fight in full:

Round 1: Cost of installation
The cost of installation depends on any number of factors – size of property, type of installation, make and model and you should get several quotes for both in order to accurately compare costs. This YouGen blog has suggested biomass installations start in the region of £10,000. Air source heat pumps can be much less – from around £4,000 (ground source heat pumps are much higher because of the heat exchanger must be buried underground). However, because heat pumps are most efficient when used with underfloor heating this can bump the cost up dramatically, particularly in a retrofit, bringing it on a par with biomass.

Winner: Heat pump in a new build, biomass in a standard retrofit.

Round 2: Operational costs    
Domestic biomass boilers usually run on pellets, heat pumps on electricity. Both are subject to the vagaries of the market. However, the Biomass Energy Centre’s comparison of domestic fuel prices claims that while wood pellets cost 4.1p/kWh (kilowatt hour) electricity costs closer to 15p/kWh. This isn’t the whole story of course, because the efficiency of the system and energy efficiency of the house must also be taken into account.

Assuming you’ve chosen an excellent, well rated (on YouGen!) installer, then the quality of your insulation is your next variable. Whilst in a very well insulated house a properly sized heat pump would require very little electricity to get up to temperature, the reality is that most UK properties are not up to standard. This isn’t to say it is impossible but if your insulation isn’t great and you lack the inclination or the funds to upgrade it, your cheapest option is undoubtedly biomass.

Winner: Biomass unless it’s a new build or complete remodel.

Round 3: Maintenance
When properly installed, heat pumps should be fairly maintenance free, usually requiring little more than an annual service. A biomass boiler, because it is a combustion system, is arguably more prone to things going wrong though again, choosing a good installer and a good manufacturer should help to mitigate that.

Winner: Heat pumps, just.

Round 4: Usability
This is a tough one. Unless you are a technical wizard who likes figuring out excessively complex programming systems, a heat pump requires an engineer to program the flow temperature (the temperature of the water in the pipes). But then, once its set, if it’s a well thought out system, you should be able to control the room temperature via thermostats and zoning.

The major game changer here, is fuel. Unless you get an automatic feeder, biomass boilers require manual loading of the pellets into the hopper, which if you’re older, immobile, (or a bit lazy!), will present a problem. Furthermore, biomass provides almost instant, flick-of-a-switch heat, which is familiar to most people switching from oil or gas. Heat pumps operate at much lower flow temperatures, meaning they take longer to get your house up to temperature. If you install a clever smart system, or have it running at a low temperature all the time, then this shouldn’t be a problem but it can take some getting used to.

Winner: Biomass if you’re agile or install an automatic feeder (can be pricey) or require instant heat, heat pumps if you’re not.

Round 5: Economy of space
While a heat pump takes up little more room than a combustion boiler on the inside, and requires a relatively small space for the outdoor unit, a biomass boiler is much more space hungry. Add to that the fact that you need a (dry) space in which to store your fuel and heat pumps, especially in urban homes where space is at a premium, start to look much more appealing. Ground source heat pumps of course require a large garden or the capacity to dig a deep trench, in order to be viable.

Winner: Biomass where space isn’t an issue, otherwise heat pumps (so long as your insulation is up to scratch)

Round 6: Government incentives
The rapid growth in the biomass market has, in part (or in full depending on who you speak to), been attributed to the fact that biomass is far more attractively incentivised under the renewable heat incentive. Tariffs are currently set at 7.3p/kWh for air source heat pumps compared to 10.98p/kWh for biomass boilers, (the rates are 18.8p/kWh for ground and water source heat pumps to offset the much higher cost of installation). Biomass is due for further degression to 8.93p/kWh for all new applications from 1 April 2015 so if you’re considering it, now’s the time to act.

Winner: Biomass, currently, though this may change in the future.

Round 7: Carbon saving
Heat pumps use electricity to operate, and will use more in very cold weather for an extra boost when they just can’t extract enough heat from the air (which is ironically when you need them most). While this doesn’t always make for low bills (see 2, above), if you buy your electricity from a green supplier such as Ecotricity, you can still claim your system is carbon neutral.

The biomass industry has long claimed that biomass heat is near carbon zero. But this is only the case if the pellets are sustainably sourced (from a forest with a strong re-planting programme), produced and transported. The campaign group Biofuelwatch has claimed that even with the government’s biomass sustainability criteria coming into force next month (April 2015), it is far from clear that biomass can rightfully claim to be carbon neutral.

Winner: This is the subject of heated debate and it’s too tough to call. If you’re confident in your pellet supply then biomass. If you only buy green electricity, the heat pumps are a good choice too.

If you are in an urban area, where space it at a premium or if you are older and do not want to manually load your pellets, you should consider a heat pump. However, this should only be done if your house has maximum levels of insulation, or you are prepared to go to the expense and upheaval of upgrading. In all other instances, particularly if you have plenty of storage space and a good ongoing guarantee and maintenance plan, or if you’re not prepared to adapt to a new way of heating where your system is on all the time, biomass is probably the more attractive option.

Photos: 1, 2 SuperHomes. Also note this helpful article on the pros and cons of biomass boilers from an owner on the SuperHomes website.

More information about Biomass Boilers on YouGen

More information about Heat Pumps on YouGen

Find an installer.

Need help with any Jargon?

If you have a question about anything in the above blog, please ask it in the comments section below.

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11 comments - read them below or add one


woodenergyComment left on: 6 May 2015 at 7:36 am

Heating pump is a system or device which working by electricity to collect heat from the cooler space and move to warm place. It's make the cool place cooler and warm place warmer. It's the alternative air condition system and also besides that biomass wooden heating system is also heating the room and boiled and stream water or any kind of application which is a environment friendly green heat technology system. It's a very cost free heating energy system and also safe your electricity bill.

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HeidiPComment left on: 1 May 2015 at 1:23 pm

After my experiences I would avoid biomass now.  I had an Extraflame LP14 installed in March 2012 by a company based in the Wirral (I am not sure if I am allowed to mention them).  The installation was problematic they didnt calibrate properly, it kept breaking down, they didn't want to come back and fix it.  The boiler has finally given up the ghost this February, some 23 months after commissioning and after numerous breakdowns.

Good luck to anyone who ever gets a serious breakdown  The boilers are manufactured abroad - the manufacturers don't want to know and refer you back to the installer.

Unless you have a really good installer you get nowhere.  Mine had done a campaign in this area as rural, yet are 200 miles away and have no intention of ever servicing or assisting. 

we have now been without heat and hot water for three months.  We lodged a formal complaint - now the industry regulation is a whole other load of contradictions.  The complaint went in on 25th March.

Today we have heard that the installers based in the Wirral have ceased trading on 17th April. 

I am in tears.  £10k on a system that doesn't work.  Nobody taking ownership and helping.  No heat.  No hot water.  Nobody to help us with this. 

I am afraid the whole industry stinks. 

If I had known any of the issues about breakdown, service, lack of regulation, inefficiency of systems beforehand I would never have gone down this route.


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Sandy Tod

Sandy TodComment left on: 1 April 2015 at 10:20 am

I would advise against anyone installing a biomass pellet boiler unless fed automatically from bulk storage, In 2008 I replaced my oil fired boiler with an in-house manually fed corner pellet boiler with the idea that heat from the boiler itself would also provide space heating in the house. It was a disaster. The Italian boiler itself didn't live up to performance expectations, the crucible burner melted and had to be replaced at 6 month intervals, under guarantee, but the installer fell out with the manufacturer so we ended up not being able to get spares. Apart from that the boiler had to be fed daily and de-ashed weekly. Not only hard work but you still need storage space for 2 tonnes of 10kg bags so you might as well have a hopper. Another drawback is we regularly go off to Aus for 3 -4 weeks in the winter and you can't heat your home unless you can get a kind relative or neighbour to come in and feed the boiler etc. I ended up ripping it out with my bare hands and scrapping it. In 2012 I installed an Okofen fully programmable pellet boiler in our garage with a 3 tonne capacity flexible hopper with automatic feed. This is 93% efficient, and runs like a dream. It needs de-ashing once a month in the winter months. I have had no breakdowns and annual service costs £125 including VAT. The 3 tonne hopper only just fits into the garage though and 3 tonnes seems to be the minimum the pellet suppliers will deliver in bulk. The whole installation cost an eye-watering £18,000 but with the RHI I will recoup that in under 7 years. Pellet supply is not a monopoly and I shop around. I live in a Yorkshire Dales village and am hoping I can get some neighbours to go for pellets so that we can set up a buying consortium.

I also think there's a wider issue here - I looked into Ground Source Heat Pump as an option but would have had to drill two boreholes as we live on limestone. Our electricity demand would have tripled. If we all go for heat pumps national electricity demand will soar. The pellet price will rise as demand grows but that encourages more supply which encourages managed woodland, which helps the environment in other ways such as reducing run-off, stabilising soils, increasing biodiversity and brings employment into rural areas currently in decline.

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RobertPalgraveComment left on: 31 March 2015 at 4:56 pm

My experience with a 14kW ‘low temperature’ air source heat pump has been perfect so far. Some of your critical observations are points to be aware of but they can in my view largely be handled by correct design and a good installer. With the proviso of course that the property is suitable for a heat pump – it needs space for the pump on an outside wall which is not immediately outside a neighbour’s window, and radiator up-sizing might be problematic in small houses.


However, with the new ‘high temperature’ systems, bigger radiators are not required.


My complete system cost a shade under £10k installed in August 2014 with 8 larger radiators and a new 250l HW tank.  The installer (GSM Ltd of Newent) also removed the old combi boiler and the oil tank in that price)


The ASHP has heated a 1965-built three-bedroom chalet bungalow D-rated house of 182 sqm through this winter using the following electrical energy input per month.




Oct. 219 (239)

Nov. 512 (137)

Dec. 827 (147)

Jan. 877 (157)

Feb. 833 (200)

Mar. 577 (318)


TOTAL 3845 (1198)


(the figures in brackets are generated units from my solar PV installation)


We have the heating on 18x7 as we are retired and we have not been away for any long winter holidays which could have depressed these numbers.


The supplier forecast that the pump would use a total of just over 7000 kWh in a year for heating and HW. I estimate that we will actually use under 5000kWh based on Oct-March being 3845 kWh. I suspect one reason my consumption is lower I because we keep the house at 19deg and not 21. Another is that we get most of our hot water free via solar PV.


I cannot give a figure for the SPF as I don’t have any way of measuring the heat I use.. But it is likely to be at least 3.0 based on the estimated (and likely) heat and HW demand of the house of around 22,000 kWh per year.


At 15p per unit, my annual heating and hot water costs would be £750. But as I get some of the electrical input from solar PV, it is actually rather less.  My oil-fired system was costing me over £1200 per year in fuel costs with annual routine servicing of about £100 plus exceptional repairs. And the hassle of having to monitor the dipstick level in the fuel tank to decide when to buy more oil etc.


The level of comfort we have enjoyed with the ASHP is far far superior to that we had with the old oil fired boiler. With the outside air temperature well below zero the house has never not been warm enough, and the ASHP outside unit has not frozen up. The low temperature supply to the radiators gives a more even heat distribution – more convection and less radiation, which subjectively at least seems less draughty.


You mention the complexity of programming. My view is that a heating system needs to have a lot of flexibility to balance the need to conserve fuel and to maintain the required comfort level. Yes the ASHP is complex, but that complexity means it can be fine-tuned to operate close to optimum. It needs a good installer, and maybe 30 minutes learning by the home-owner to understand how to use the settings they are allowed access to.


When it comes to carbon emissions, a heat pump running on grid electricity is producing heat at about 200g per kWh (ie 600g/kWhe divided by an SPF of 3). This is comparable with a gas central heating system (typically held to be190g/kWh )


With my solar PV and the fact that I buy electricity from Good Energy, the real carbon footprint is considerably lower. And as the national grid decarbonizes further in the future, Heat Pump heat will become even more advantageous compared with oil, LPG and even natural gas.

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KeithSComment left on: 31 March 2015 at 8:20 am


Heat pump or wood burning.

Having made our house as energy efficient as we could, we came to point a few years ago, where, out of necessity we had to choose how to heat it.   At the age of 75 ease of use and convenience were important considerations.

We could probably have had a wood burning stove but we decided against it for the following reasons.

Where could we store the the all the wood we would need   ?   
It may be easy to get right now but as more and more people climb on the band wagon  would it still be as available and cheap in a few years ?    I doubt it.
We haven’t got the space for anything  much larger than a gas fire  so bio mass boilers weren’t an option.

Before we had our small extension built we had a gas fired back boiler, that became obsolete .   As a temporary measure we used a 2kw convector heater in the lounge and found that that kept the house quite warm.   With that experience ( and a lot of reading ) I became convinced that a heat pump  would be able to do the job. 

We had an air to air heat pump installed at a cost of £1250.  Its a relatively simple installation,  The outside unit and the inside unit are  on opposite sides of the wall joined by about 2 metres of copper tubing.   Its made by  Mitsubishi and rated at 1kw.     My best estimate is that it uses about 500w  because our total electrical consumption is about  25 kwhrs per day during the winter. The old radiators have now all been removed.  That in itself is quite nice.  We also have solar panels which were installed almost 5 years ago.  Last year the feed in tariff matched our electricity bill.   
For us at least,  an Air to Air heat pump was definitely the way to go.

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greenderbyshireComment left on: 31 March 2015 at 5:41 am

Hi Guys,

having just read the comments above, I think there are a whole load of points that have been missed and some that have been misrepresented. Here is my take:

Costs seem to be the main thrust of these discussions.  So firstly if someone new to the scene read these articles they would be thinking biomass is only about pellets!  

We run a log fired Biomass system and it is considerably more economical/cheaper to run than any of the systems referred to above.   Our heating/DHW costs per year are around £300-400 for a 4 bed detached farm house.  So if it is all about running costs then Log Fired BIOMASS systems win hands down.  

Comments from above................

"A biomass boiler is a fire.  It has to be on all the time.  A lot of heat goes up the chimney in MOST installations.... a lot of ash ..........."  

With respect, these comments are highly misleading and in the case of MOST if not all log-fired biomass systems, totally inaccurate.

Our system is batch fired and does not have to be running all the time, as it feeds a properly sized buffer storage tank.  DHW and central heating are then run from this heat store, controlled by a series of thermostats - a very efficient system in a well insulated house.  Yes in winter we have to run the boiler from cold once each day, but in spring and autumn this is once every other day and in summer once a week (purely for DHW).   The wood ash produced from one burn is very small, these systems are very efficient (90%+).   Gases driven off by the burning process are recirculated back into the fire chamber.  Batch-fired boilers are never damped (restricted O2 follow) and run at a temperature that produces near perfect combustion and maximum efficiency.  I will stand corrected but my understanding is any system, including pellets, that runs with a standby mode (fire always in) will be inherently less efficient.

Biomass boilers with a buffer system win the efficiency contest by a mile.

OK now the down side(s)........   We buy wood from a tree surgeon and have to cut and split it ourselves.  This takes a time and effort.  Logs require storage and also on a daily basis, physical effort to transport them from the wood store into the boiler house.  Running the boiler is a 20-30min operation each time it is run.  So it is not all "roses", but beats using electricity produced by dirty coal-fire power stations by a mile, as is the case for heat pumps.

Regarding the "being green"  comments above - these of course are abstract concepts, as is the requirement for the wood to be from a sustainable source. The wood we burn is waste - tree surgeons don't just go around cutting down trees so they can sell the wood to people.  If we didn't burn it, someone else would.  "Sustainable" sources cut wood just to make pellets, so I fail to see how that is better than "recycling" waste wood.  The only thing the Government has done by making sustainability a requirement for RHI is to preclude people like ourselves qualifying.  This is a very poorly thoughtout policy.

So log-fired biomass is not for the average or faint hearted person.  If you want convenience then use a mains gas combi boiler. Heat pumps are all right, but the electricity needed to power them has to be produced somehow.   We all need to get real about national power generation if we want to be "green".    

While I am on my soapbox, why oh why do wind turbines get such a bad-press these days?  Once up, they are totally clean and have minimal impact on public amenity (unless you are a protester!) and can be taken down if/when they eventually harness the nuclear fusion process.

Yes you guessed it, we also have a 15KW wind turbine, which will very soon be dumping electricity into our Biomass buffer tank, via immersion heaters. This is the way ahead, locally generated electricity heating your house, super clean, super efficient.


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ShepsComment left on: 30 March 2015 at 10:46 pm

Biomass energy centre ( Dec 2014 figures for pellets are 6.81p kwh @ 90% efficiency. Prices for pellets have gone up since then.  The pellet market is looking increasingly uncompeteitive.

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sdelengComment left on: 30 March 2015 at 10:30 pm

There you are - I rest my case.

As I wrote, a lot is not addressed.  Go with tried and tested, and not with new crazes that invite charlatons with no reall experience to jump on the eu grant band wagon. A biomass boiler is a fire.  It has to be on all the time.  A lot of heat goes up the chimney in MOST installations, unless properly done with one of the better more expensive boilers.  A lot of ash, just like a fire, needs cleaning out. Do not be folled by electronic versions (a nightmare) and autoatic ash cleaners. The ash still has to be disposed of. I would like to see how many people would opt for a wood burning car...

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Ben Whittle

Ben WhittleComment left on: 30 March 2015 at 9:38 pm

ASHP for £4k and biomass for £10k? Good luck with that!

Having worked for 3 installation companies I can tell you the chances of getting a good installation at those prices is not even slim.

I would take issue with most of the points raised in this article - I appreciate it's not easy to summarise all the detail in a short punchy article. But my advice would be to stretch it out to a series of articles or write a longer one instead!




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sdelengComment left on: 30 March 2015 at 8:35 pm

This article is interesting but far from complete.  A biomass boiler needs LOTS of daily or weekly care.  The automatic bit rarely works as the burn rate of pellets, olive residues,almonds ar whateer create a different ash and problem.  It has to be on all the time so actually uses more fuel than stated.  In the countryside, it can actually smell bad, more than in a village where the chimmies go high above all.  The price of pellets is quite frankly a monoply.  If you have an oil boiler, the cost inscludes free delivery, but the pellet guys add a MASSIVE delivery charge.  They have to pour the stuff into your giant silo, and if you do not have a giant silo, poor you.  No option for good prices. And it goes on.  

I am removing my BIomass boiler for which I got a 68% grant from the EU.  As soon as they pay, out it goes and anyone can have it for free.  i am going for oil.  Not even heat pump.  Off when I want it, on when I do.  Perfect control, less use.  Cheaper in the long run (by the way I have places in several countries with different systems so feel qualified to comment).

Read 10 things they never told you about biomass boilers - and think eco waste of Agas.


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MikelComment left on: 27 March 2015 at 2:28 pm


Some comments for you based on our experience.

We opted for a GSHP/Solar thermal DHW but had a quote for a biomass boiler as our installer reckoned they were a good deal (Autumn 2012).

Cost of installation: Similar. We would have had to build an outside boiler/hopper shed for the biomass boiler.

Operational costs: We upgraded our radiators to allow for a lower flow temperature for the GSHP (50C). This proved to be a bit more expensive than planned as we found the original radiators had been fixed to the plaster board and not properly secured! We had the SPF for the system re-assessed for the RHI and that came to a figure of 3.1. We have meters installed so we can measure our actual SPF, which comes out at 3.4. This makes the cost of electricity equivalent to mains gas. I would make the point that under floor heating systems may be ideal but not essential for a retro-fit ASHP or GSHP.

Maintenance: I asked about potential maintenance costs for a biomass boiler and was quoted £250. Our GSHP doesn't need much if any maintenance but ASHP may require more. We also have to have an annual unvented DHW cylinder check, cost £30. The solar thermal system is recommended for an anti-freeze check every 5-8 years.

Usability: Agreed the GSHP requires some expertise to program but once set up doesn't need altering. The point about manual loading of pellets is well made.

Economy of space: The GSHP takes up little more space than a domestic fridge. It won't quite fit under a work top and there is need of space for the 80L buffer tank. Ours went in our utility room. It does, however, make a little noise, so you would need to shut the door on the room.

Government incentives: Ours is classified as a legacy system for the RHI and our deemed heat load was lower with the most recent EPC/GD assessment. It should be much easier to model the various systems to get a more accurate figure of potential return now.

Some items that you did not cover:

Life of the system: Not sure how long the biomass boiler will last before replacement but we are hoping for 20 years for the GSHP and probably at least double that for the ground collector.

Future energy costs: I don't have a crystal ball here! However, I did take the view that wood supply may not scale as more and more of these systems go in. I think also that electricity has considerable flexibility of supply and we have PV installed, which will permit some usage in the shoulder months. Whilst all estimates are made on the basis of current costs, we know that those costs vary, as it has with the drop in the price of oil.

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