UPDATED: Air Source Heat Pumps/Air Con - Full Info & Guide, is it cheaper to run than mains gas?

rhubarbe

I have electric underfloor heating in our kitchen and main bedroom (it's a bungalow). Electric UFH is so hideously expensive to run that we never actually got to switch the bedroom mat on. The one in the kitchen was costing us 30 quid a week. So far this winter our ASHP has cost us no more that 17 quid a week and that does the whole house.

Electric UFH is however, very easy and quick to install - and very very profitable for the builder.

About the only use I would recommend for Electric UFH is as a bivalent back up to an ASHP - that's what we'll use ours for now if it gets too cold for the heat pump. It hasn't yet.

albyota

If any body is undecided about whether to purchase an air to water heat pump yet, this could help you decide, the CERT funding from Mitsubishi/BG. this does not affect the RHI (Renewable Heat Incentive), you would still get it.

e.g. 3 bed detached house, replacing soild fuel boiler to heat pump you get a one-off payment of £1,067
e.g. 3 bed semi, replacing electric to heat pump you get a one-off payment of £633
e.g. 3 bed detached house, replacing oil fired to heat pump you get a one-off payment of £359
http://domesticheating.mitsubishielectric.co.uk/cert/cert_banding

Bubbagirl

We moved into a new property 2 years ago, it has an Altherma Air source heat pump. We were told that it was very cost effective to run and were please to have something new and planet friendly.

The system was never set up correctly by the housing developer site manager (who thought he knew it all and was left to do the set up so the developer could save money) therefore the first year we had major problems, the system costs us about £3000.00to heat for the year for a 6 bedroom house, please note there may be six bedrooms but being a new build, its the size of a decent 4 bedroom but we have 2 bedrooms in the loft space. Last Xmas (2009) we took out a contract with Spaceair to maintain the system. Cant fault them at all, good customer service but the maintenance contact was £200+ for the year. By this time the system was set up properly.

We had been told by the developer that the most efficient way to run the heating system, was to leave it on 24/7 with the radiators on about 2. We did this, yes it was nice and toasty all last winter but bloody hell did we pay for it!:( We had a sort of quarterly bill for about £800.00. After that quarter we have the heating on schedule times to reduce cost, and as a side problem we are now in dispute with our electricity company because our summer quarterly bill £680.00 with no heating on:mad::mad:.

We dont know whether this system is causing excessive electricity use but we now are doing two meter reading a day. I wont go into all that as its another matter really, but I wanted to say that as soon as the frosty weather starts, the outside air pump on this system, revs its guts out to get to reach temperature ( and no its not that quiet!:() and its started using a hell of a lot of units, we don' believe this system is cheap to run. Today I have contact Altherma Daiken to ask their advise.

To sum up, I don't know whether its expensive, if we've just been really unlucky but I wish we never had this system

rhubarbe

We only have a 3 bedroom bungalow but the rooms are a decent size. We're running a Mitsubishi Ecodan 8.5kW. Last week we used 231kWh (about £22) in total for electricity and that's ALL our power and heat. This gives us a warm house from six in the morning to half eleven at night, and all our hot water. Last Winter the LPG boiler it replaced cost £1 an hour to run; the elctric underfloor mats in kitchen and bedroom cost £30 a week to run; and we used a bag of coal a week at £15; plus loads of logs we'd spent all Summer sawing and chopping.

I suggest there is something not right about your Altherma installation..

Bubbagirl

Just thought I would clarify, just in case, although I think its for another forum, we cannot pin excessive electricity usage to the Altherma system, as for the summer quarter, we did daily meter readings and for the first 17 days, the usage was fine. We would have expected at least 60 units a day to have been used to equal the bill we had. We were using about 12 units. Only the water was on over the summer months.

We know this cant really happen unless someone has tapped into our electricity but our meter has seemed to have jump on/added about 2000 unit per quarter, something that the electricity company say is impossible! The fight continues but the Altherma system is questionable.

rhubarbe

In that case I feel that you have no choice but to take your readings every day..

mitchy74

Got the results to my Heat Loss Survey today....

According to the womans workings I have a loss of 8kw in my current building and 4.7kw in my extension (when its built) totalling 12.7kw.

Thats all very well but I dont have a scooby what that information means, and what impact it will have on the size of ASHP I will need..... not trusting the sales guys very much, can someone advise?

Cheers

albyota

The problem with the Daikin Altherma, is, it has electrical back-up heating elements fited in the hydrobox, if incorrectly sized or undersized these elements come on to 'boost' the heating, this of course is very expensive, the Mitsubishi Ecodan does Not have any electrical element boost (apart from the hot water for thermal disinfection once a week), service and maintenance (Optional if at all required is £75/yr).
I hope you get it sorted, spaceair (Daikin) are generally good but will never Knock their own systems.
Incidentally my 200M2 house costs £850/yr total running costs, I have the 8.5kW Mitsi Ecodan, no other fuel.

albyota

mitchy74 wrote: »

Got the results to my Heat Loss Survey today....

According to the womans workings I have a loss of 8kw in my current building and 4.7kw in my extension (when its built) totalling 12.7kw.

Thats all very well but I dont have a scooby what that information means, and what impact it will have on the size of ASHP I will need..... not trusting the sales guys very much, can someone advise?

Cheers

Hi. mitchy74, That means the u values of your walls, windows, floors, ceilings, roof collectively all lose heat at a rate that require xxxkwh to replace that heat...if they have used building regs/CIBSE guide they would have used minus 2 outside and 21 degrees inside...you have to ask yourself whether that will be good enough when it is minus 8 outside......get some more quotes....you will soon understand what it is you actually need. The most important things to consider are the size of the radiators, and the flow rate of the equipment being specified, shout if you need any help.

mitchy74

Looking at the report its -5 to 21c she has used in this instance. She has also noted that she hasnt allowed for hot water heating (I dont use much anyway).

In super simple terms.... to acheive a temp of 21c at -5 outside I need 12.7 kw of a boiler as an absolute minimum?

When getting quotes previously from Ice they were suggesting getting 2 8.5s installed but I was pushing to get a 14 with the existing new LPG boiler as a boost if need be. Bearing in mind I also have a log fire at one end of the house and a log burner in the middle that would also be retained.


Edit - again thanks for all your help! as mentioned before I really like to try and understand these things before going ahead so not to get fleeced! The Ice bloke was suggesting that the Govt were due to announce the RHI in the coming weeks in a concrete plan.... fingers crossed altho at that point it will probably be nigh impossible to get an installer for months.