Air Source Heat Pump for 2 bed bungalow

Cardew

matelodave wrote: »

I'd argue that if a property needs 15,000kwh for heating & hot water then it needs that from what ever source you feed it with whether its a heatpump, immersion heater, gas, oil or wood boiler.
The difference being how it's delivered and how much it costs.
Using an immersion heater with electricity at 12p/kwh it will cost £1800 a year. Using a gas boiler at 90% efficiency it will take 16500kwh at 4p a kwh = £660. Using a heat pump with a COP of 2.54 = 15000/2.54 = 5900kwh x 12p/kwh = £708 which compares pretty well with gas. If you get the system set up properly and can average a COP of 3 then it's cheaper than mains gas at only £600 and a lot cheaper than oil or LPG.
I would agree that if it's not designed or set up properly and you aren't comfortable so you've got it flogging away all the time at a high flow temperature then it won't be cost effective.
If the heat emitter's can't deliver the 15000kwh hour to the house at the optimum flow temperature then it will be cold, the only way to counteract that is to increase the flow temperature until they do, but that has an adverse effect on the COP. That's why most retrofits using existing radiators don't work - you need rads or whatever to be correctly sized

I chose by words carefully, but I obviously have not put my point across; so I will try again!


This hypothetical house with an ASHP needs 15,000kWh (delivered) to maintain the property at the desired temperature for the occupants. To illustrate the point I am making, it doesn't matter about the COP(or the cost of electricity). It will use 7,500kWh with a COP of 2.0 or 5,000kWh with a COP of 3.0.


As said earlier by thee and me, an ASHP has to run much longer because of the low flow temperatures. For people out at work, and when in bed, the ASHP is producing some of those 15,000kWh when the house is unoccupied or occupants are in bed.


Now because a conventional gas/oil/LP can produce water at 80C if required, it is not necessary to be pumping out heat while the house is unoccupied or occupants are in bed. For instance I set my heating to come on 20 minutes before I return home and 20 minutes before I get up in the morning and this gets the house sufficiently warm.


So your calculations above would be valid if it needed 15,000kWh delivered by gas/oil CH. However the point is that with gas/oil it doesn't need 15,000kWh to achieve the same degree of comfort for occupants as it is not producing heat while the house is unoccupied or occupants are in bed.


Thus in making comparisons between running costs it is not valid to compare 15,000kWh delivered from an ASHP with 15,000kWh delivered from a gas/oil CH system. Depending on circumstances a gas/oil system might only need to deliver, say, 12,000kWh.


The EST acknowledge the above is correct, albeit it is not possible to quantify the differential as it depends on the occupants circumstances.

patman99

Lovesgshp have you read the thread ?. The op is asking about the less efficient Air Source Heat Pump. I have a feeling that they are opting for this as they have no desire to either have a 200ft deep hole bored in their garden, or a large pit dug to bury the heat-collecting pipework.

Op, have you considered 'thermal wrapping' ?. This involves quite literally fixing insulation to the outside of your property and then rendering it for protection from the weather. This would reduce your heating bills massively.

As for ASHPs, I have read-up on this and the general consensus is that they are cheaper than oil fired heating, but not as cheap as gas or heating with oil-filled radiators. They also lose efficiency as the temperature drops and can actually freeze up if you don't have a heater pack installed to keep them warm in winter.

lovesgshp

@ Patman99:
Yes I have read the thread and do know the difference between a ASHP & a GSHP. After all, we have been installing both types in Italy since 1999.
I think you are referring to my comment in post 9, which was meant to just show the effect of the range change.
In no way was I inferring that the OP should have the other system.

Cardew

patman99 wrote: »

As for ASHPs, I have read-up on this and the general consensus is that they are cheaper than oil fired heating, but not as cheap as gas or heating with oil-filled radiators. They also lose efficiency as the temperature drops and can actually freeze up if you don't have a heater pack installed to keep them warm in winter.

Certainly an ASHP working properly will be cheaper than oil central heating in most cases.


However if by 'oil-filled radiators' you mean plug-in electrical radiators filled with oil(or any other substance e.g. water/clay) then an ASHP is much cheaper to run. Oil filled radiators will cost, say, 12p/kwh where an ASHP will normally cost between 4p/kWh to 6p/kWh when using electricity on the same tariff.

plumz_2

Thanks to everyone who took the time to reply, I'm aware of the issues regarding standard radiators hence me mentioning about getting smart rads in my original post.

Does anyone have any thoughts on the insulation levels? External wall insulation is not an option. What about the floor? How important is floor insulation?

I have no heating at all atm. I definitely do not want oil or lpg and i have no access to nat gas.

So its either ASHP, storage heaters or panel heaters.

matelodave

What sort of floor have you got? some can be a lot more difficult and expensive than others to insulate and I'm not sure that the returns justify it. If you are pulling up the old one and replacing anyway it then it's worthwhile and I'd say go ahead.


I've got an overlay wet floor heating system on top of a ventilated wooden floor, which we chose not to insulate. A decision I do regret a little bit as I reckon I could save even more money on my heating bills. However the cost, time and effort in pulling up & replacing all the flooring and stuffing insulation under them would have probably taken me at least 10 years to pay back and added another two weeks to my very tight schedule and a lot of money to my very tight budget.
An alternative which I could have considered might have been 10-12mm foil faced Kingspan or Celotex under the overlay but it's too late now as its all down and working fine. The overlay stuff is 18mm plus 6mm ply on top so we had to take 25mm off the bottoms of the doors - another 12mm or so wouldn't have caused us any problems.


We have the advantage of cavity wall insulation - although I'm not sure how good it is as it was installed when the bungalow was built in 1986. We've got 300mm of loft insulation and double glazing (1999 vintage) so we are reasonable but no where near current building standards.


I reckon it's easy to get into the realms of diminishing returns where you end up spending a lot more than you'll recover in a reasonable period of time, if at all. Spending £1000 just to save £100 a year takes 10 years to pay back so you do need to do your sums before jumping in.


The marginal cost of our heatpump over an LPG or oil/biomass system was around £3-4k and I guess we are saving at least £500 a year on our electricity bills, so payback is 6-8 years (or less if we eventually get the RHI). Also we didn't want a ginormous gas or oil tank in the garden nor even a big heap of wood or pellets together with the inconvenience of deliveries etc.


We've had it now for 3.5 years, so about half of it's capital cost has paid back already

[Deleted User]

plumz wrote: »

Thanks to everyone who took the time to reply, I'm aware of the issues regarding standard radiators hence me mentioning about getting smart rads in my original post.

Does anyone have any thoughts on the insulation levels? External wall insulation is not an option. What about the floor? How important is floor insulation?

I have no heating at all atm. I definitely do not want oil or lpg and i have no access to nat gas.

So its either ASHP, storage heaters or panel heaters.

Hi, I have the Dimplex SmartRads, thirteen of them!, mated to a 14kw EcoDan for the last 3 years ish. By no means are they totally silent but they work very well and with the white glass front look good too. Also have wet UFH and a regular towel rail in the bathroom.


Size them on their lowest fan speed and you wont go wrong. With our heat curve settings they typically run off water at 38c during winter. I have tried lower, 25c, successfully but UFH was useless that low. Having both UFH and the fancoils I prefer the latter for faster warm up times and shorter run times.


Current paying Eon £94pm for everything but we do have solar PV so often get free heat if its sunny. This is in a 100+ year old station obviously detached with high ceilings, carp insulation compared to a new build etc. Bigger than most 4 bed new builds which I think is very good. Occupied during the day too... If only I could bin the wife and child usage would plummet, hair dryers, hair tongs, tv 24/7, oven, computers, dvds, music, lights, endless chargers...........................



As the ASHP/heat emitters are sized correctly, i.e. no booster heater, there has never been an issue heating the house even if minus double digits. Cold season running time is approx 10 hours per day, well that is what the timer is for but obviously does not run all that time if you see what I mean.


Having had oil and lpg in the past I cant recommend them unless you are very frugal whereas the house is always warm with the ASHP.


Hope this helps but looks like you have had loads of great advice already...

plumz_2

Im starting to realise that an ASHP is cost prohibitive, if i need to insulate so well to make it work. Without the cost of insulation it will probably take me 7 years to get my money back, add the cost of insulation of top and it look ridiculous spending that amount of money on a 2 bed bungalow. I might not even be in the same house 4/5 years time. The cost of these renewables needs to come down by half in price to make it viable for most people.

I have even thought about solar panels too but again the cost is ridiculous, even if i fit it myself. If i do fit it myself i cant claim rhi, probably because im not deemed competent. This MCS scheme is a load of bs, you can have companies like Everest MCS certified, but there blokes are not, they dont even need to go on a course as long as the company has. Absolute joke.

I might just put some cheap storage heaters in then see in a couple of years if the price of solar has gone down. I want a comfortable warm house but i dont want to bend over and take it to achieve that.

Thanks all