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Air Source Heat Pump vs Oil Boiler


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Hi,

I've been reading that in the lifespan of an ASHP vs a super energy efficient oil boiler that the oil boiler is in fact the least costly option. Obviously there is going to be fluctuations in oil price etc But even with the tariffs available for the ASHP the Oil Boiler comes out on top financially. Does anyone have any experience of this? Or compared both?

 

Thanks

 

Paul

Edited by paulc313
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People who have been there and got the tee shirt will be along shortly but for me the issue is two fold. 1. The embodied energy / carbon in making the equipment which needs to be part of the equation and 2. The carbon created in driving the system EG from the oil in one case and from the grid / PV in the other. Once you factor these in to the total cost to the planet you may get a different answer.

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If you are looking purely at a price comparison over a fixed period of time, then an oil burner is possibly the cheapest.

That price comparison would vary depending on where in the world you are, your overall energy needs and cost of servicing.

 

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Best to look at this as a sum of two parts, the capital cost associated with purchase and installation and the whole life running cost.

 

An oil fired boiler will be perhaps half the capital cost initially, and likely have a real-world efficiency of around 85%.  For any given heat output the running cost can be estimated, and this will vary with the price of oil.  If you had a house that needed around 5,000 kWh of heating and hot water a year at today's oil price of around 50p/litre, and assuming that 1 litre of oil gives about 10.5 kWh at 100% efficiency, then at 85% boiler efficiency 1 litre of oil would deliver just under 9 kWh.  To meet the notional 5,000 kWh annual demand the boiler would burn about 555 litres of oil, at a cost of about £277 a year.

 

An ASHP would cost more initially, and would have a real-world efficiency of around 300%.  For the same 5,000 kWh annual demand, the ASHP would consume about 1,667 kWh of electricity, and if run on a standard tariff of about 15p/kWh would cost around £250 a year.  However, we run our ASHP almost exclusively on the Economy 7 off-peak tariff, which only costs 8.148p/kWh, so using that tariff rate 5,000 kWh of heat (1,667 kWh of electricity used) would cost about £136 a year.

 

In addition to the above, servicing costs need to be taken into account.  An oil fired boiler is likely to always need an annual service, at around £100, whereas an ASHP is pretty much maintenance-free, all it needs is an occasional external clean.

 

The question then becomes one of whether the potential saving over the life of the unit will justify the difference in the installation cost.  If the house is pretty poor thermally (say, built to only just meet building regs) then the chances are that the RHI payments that the ASHP installation would attract might well cover the installation cost difference.

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@JSHarris I've just been to a home building roadshow and spoke with some of the ASHP sellers. They advise that the ASHP needs a yearly maintenance check. They didn't elaborate on the price of this but I assume that it will be similar to the service of the oil boiler.

 

Interesting that the ASHP has different settings. I'm personally looking to build in Aberdeenshire so would I get away with running it on Eco mode if I live in a colder climate than Wiltshire?

 

The house will meet what the current build regs are in Scotland. I don't think there is going to be any more energy efficiency in the new build.

 

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4 minutes ago, paulc313 said:

@JSHarris I've just been to a home building roadshow and spoke with some of the ASHP sellers. They advise that the ASHP needs a yearly maintenance check. They didn't elaborate on the price of this but I assume that it will be similar to the service of the oil boiler.

 

 

That's because they are trying to sell you something that isn't needed.  The instructions for our ASHP are clear.  It needs a visual inspection externally once a year and, if needed, any dust or cobwebs need to be cleaned out of the heat exchanger.  It takes all of five minutes with a soft brush to do this.  There are no parts within the ASHP to maintain.  The only other check is related to the heating installation, rather than the ASHP, and that's to check that the pressure and pre-charge are OK.  This takes seconds to glance at the pressure gauge, and is something I tend to do every few weeks as a matter of course.  Putting a tyre pressure gauge on the pressure vessel and checking it similarly takes seconds to do.

 

 

4 minutes ago, paulc313 said:

 

Interesting that the ASHP has different settings. I'm personally looking to build in Aberdeenshire so would I get away with running it on Eco mode if I live in a colder climate than Wiltshire?

 

The house will meet what the current build regs are in Scotland. I don't think there is going to be any more energy efficiency in the new build.

 

 

The settings for the heat pump vary from make to make.  We never bother running ours in eco/quiet mode, as all it does is make it run for longer to deliver the same heat output.  It's very quiet in normal mode, and despite us living in a very quiet area we can't ever hear the thing running (unless stood outside right next to it).

 

If your house is only going to be built to just meet building regs then the heating requirement will be quite high (relatively speaking) and so you would burn more oil and if using an ASHP you'd get a higher RHI payment for the first 7 years.  You may find that the RHI payment makes the ASHP a fair bit cheaper option because of that.  If you improve the energy efficiency of the house, to the sort of level ours is, then the RHI becomes a bit pointless.  There is a premium for an ASHP installed by an MCS approved installer that's typically around £1,500 to £2,000, because they know that you need an MCS approved installation in order to claim the RHI grant. 

 

Taking our case as an example, the RHI payments for us would have been about £84 a year for 7 years, so about £588 in total.  We were quoted about £4,000 for an MCS approved ASHP installation.  I bought an ASHP for £1,700 and fitted it myself in less than a day (dead easy job).  The total installation cost was around £2,000.  So I saved about £2,000, but lost out on the RHI grant of about £588, so we still came out way ahead.

 

The same may not be the case if you have an inefficient house that needs a lot more heat, as in that case the RHI payments will be a lot higher, and may well cover the higher costs associated with an MCS installation.

 

As an aside, I have little experience of installing heating systems but found that installing an ASHP was extremely easy.  Just two pipes, a power cable and a control cable.  Any competent heating installer could fit one in less time that it takes to install a boiler, as there's no messing about fitting a flue etc.

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I did a cost comparison as suggested by @JSHarris prior to deciding which way to go for our house.   Taken over a 10 year period, ASHP came out on top for us against every other form of heating / fuel source (based on 5000 kWh each for heating and DHW).  Direct electric becomes viable if you have very low heating demand / DHW requirement - below 2500 kWh each. Oil couldn't compete at any level based IIRC on 40p per litre.

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@Stones Can you tell me how you done your cost comparison?

 

@the_r_sole Were thinking about PV panels to get it through the regs plus high levels of insulation (to be honest I don't know what the insulation levels will be, my father in law builds houses for a living so he is basically the project manager for that)

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from my experience of having commercial air con and refridgeration units ,which really are same as ASHP

then I would be very suprised if an ASHP did not last longer than any sort of modern gas or oil boiler with a thin crappy heat exchanger  in them 

the modern self condensing ones rot the away pretty quickly ,even british gas say you should be changing boiler every 7 or 8 years and nobody will give you a total service+ parts package for  more than 5 or 6 years for a fixed yearly figure --after that you pay extra for parts --so that makes me think 7 years is about right time for trouble free running of boilers.

I could be wrong ,whats the longest somoene has had a an ASHP? 

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Oil boiler needs an annual service, about £120 here, and there is no DIY option unless you are going to spend many £00's on a flue gas analyser and pay to have it calibrated every few years. (if you do that I don't think there is anything legally stopping you servicing your own oil boiler)

 

No ongoing costs for an ASHP.

 

Now it is summer and the heating is off, I have the hot water (via ASHP) timed to come on when the sun is up.so hot water is mostly free, and topped up by the immersion heater diverter.

 

It was the volatility of oil prices that put me off that as a fuel.  It's not so bad now, but I remember one year a few years back when the price spiked and it cost us £1200 for a years oil.

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21 hours ago, paulc313 said:

@Stones Can you tell me how you done your cost comparison?

 

 

 

I started on the basis of using the same assumptions in terms of both hot water storage and heat distribution method - so UVC for hot water storage, and UFH for heat delivery.  That way I was comparing the combined capital and running costs of connecting to predetermined systems.  Thereafter it was a case of ascertaining the (installed) capital costs of various systems - I compared direct electric (willis heaters x 2, timeclock, master thermostat / controler, circulation pump, immersion in UVC), oil boiler and oil tank, ASHP.  I assumed set figures for efficiency - 100% direct electric, 85% Oil, 350% ASHP (heating)/ 250% (DHW). Finally I worked out running costs (fuel costs) over 10, 15 and 20 years over a range total consumption figures staring at 1500kWh for DHW and 1500kWh for heating, up to 5000kWh for each in 500kWh increments. That gave a range of basic figures for each option and different usage requirements.  I also added in expected servicing costs.

 

 

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I think there is pros and cons for both options. A lot easier to find a repair guy for a oil boiler plus parts are pretty cheap (complete new riello burner £300). Regarding a comment above regarding oil boiler/gas boiler life span, i believe a oil boiler has a lot longer life span than gas. A lot of oil boilers come with a 5 years warranty, I am pretty sure I can get a worcester bosch engineer out within a few days, how long to get a engineer from Mitsubishi? We often had customers who had oil stolen from tanks. Oil service can be messy esp if inside house. I have decided to fit a ashp but I picked up a ashp pretty cheap if paying a few £k i would reconsider options.

Nothing stopping you divert excess pv with a oil boiler set up.

I think the big issue is design a house with ultra low heat requirements so you can fit/change any heat source at a later date. 

Remember dave, we didnt always have fancy flue gas analyzers.... it's part of cover your ass society I can leave the customer a nice bit of paper stating this is what your boiler is doing when I left it (for the record we where 1st in area with analyzer). 

 

Edited by Alexphd1
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When we sold our last rental property, it had a still working, and serviced, Grant outside oil Combi boiler, with a date code of 1985.  Obviously not condensing so not as efficient as a new one, but still working.

 

The plumber did say he had trouble getting the burner set up at the last service and thought it might need a new burner some time soon.

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How about a mixture of systems, could you use the oil boiler for hot water and Ashp for ufh. 

Would your opinions alter on the oil boiler if you already had one. 

 

We we have a 3 year old oil boiler sitting on a pallet from the old place we knocked down, it has been on my mind to ask these questions for months. 

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1985 still young for a oil boiler probably still 80%efficient, only thing changed for the new condensing oil boilers was adding a second stainless heat exchanger on the exhaust flue which tbh was a pretty crude add on. Prices took a big jump when went condensing.

 

If I had a oil boiler sitting on a pallet I would be using that, worst case you ditch that in 5 years time for ashp IF oil cost shot up or DIY a oil/ashp set up.

 

The cost of the grant vortexair combined heat pump/oil boiler is scary (£6k?) and has the negatives of both system... finding a oil engineer or refrigeration engineer or both! 

 

I myself fell into a over complicated system a lot to be said for KISS.

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