Posted by: @fretless6

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Hi. I'm Mike. Thank you for letting me join.

My partner's dad died in November last year and we're planning to buy his house from the estate. The 30+ year old gas boiler in the house  has been condemned as unsafe. Instead of putting a replacement boiler in I think we should be looking at heat pumps.

The situational complexity is that the estate will pay for a replacement boiler to make the house sellable, so I've got a convincing job to do to spend slightly more (on top of the £7.5k grant) for a heat pump rather than just put another gas boiler in. So first question, should I just go with a gas boiler?

I've come to a decision to make between Taggas and Aira. The Aira guy talked a better talk, but to get the 15 year warranty you've got to pay £19.90 per month for 14 years. The Taggas offering is less expensive (about £2k) and lists a separate warranty for the heat pump (Ideal Logic 7 year warranty ), the DWH cylinder (25 yrs) and 2 years for their workmanship. There is no ongoing monthly fee, which is appealing.

Does anyone have experience of Taggas and/or Ideal Logic 10kw heat pumps? Is this something good to pursue, or am I making a rod for my own back?

Welcome to the forums.

You are in an interesting position.  By the sound of it the heating system is pretty old.  If so and if this were soon to be my house, I would be thinking beyond the heat source itself. 

With a heat pump you will be getting a significantly upgraded and newly designed heating and hot water system, not just a new source of heat.  Its likely quite a few radiators will be changed and you have already said you will be getting a new DHW cylinder, which will deliver mains pressure water to all hot outlets, definitely a plus.  Very likely all your cold outlets will also be converted to mains pressure at the same time, which is also a plus (you can drink from and get decent flow from every tap!).   Done properly it is likely to be much more comfortable than a traditional gas based system, because its operating at much lower temperatures for a longer time, which means you have fewer temperature gradients in both time and space.   The controls will be more modern.  In summary its probable that its a significant upgrade which, from what you say, may be well overdue.

The downside, and there is a downside, is that because it is a whole new heating system it requires good design.  Sadly, there are some installers who don't do that consistently.  This means that, to be certain you will get a good job, you may need to spend a bit more time on researching installers - its the installer/system design that matters most, much more than the brand of heat pump) and asking some pointed questions.  People here can help and @mars can give you a name or two of known good installers in your area.

The key questions to ask are:

1. Is it right-sized?  Oversizing heat pumps can be as bad as undersizing them; 10kW is a little on the large size suggesting wither the house is poorly insulated or its rather large.  Below I reproduce a plot of about 250 systems from a popular heat pump monitoring site showing measured loss vs floor area.  Its notable that there is only one system where both the floor area is <200sq m and the measured loss in >9kW

2.  Is there a buffer tank - if so why?  (A b uffer tank is a 50l+ tank of water between the heat pump and the radiators, plumbed into both the flow and return).  In almost all cases buffer tanks are unnecessary and in far too many cases they are unnecessarily installed and set up badly compromising performance and making fault diagnosis difficult.  Aira do (I understand) fit buffer tanks but apparently set them up correctly, but in general, unless there is a very specific reason, they are something to avoid.

3.  Are lots of external controls being fitted or retained, or is the system being designed to run on the native heat pump controller only.  External controls, particularly 'smart' controls, are generally unnecessary and bad practice.  Its recommended that even TRVs are used sparingly if at all (they will generally be fitted but most should be left on maximum and temperature regulation achieved through something called 'weather compensation)

3.  Is there any performance (COP/SCOP) guarantee?  Whilst all installers will give an estimate, only a few will give a guarantee.  That should not rule out those who don't provided the other key questions are answered satisfactorily, but its worth considering.

There is an introductory article on heat pumps here which I recommend you read.

My personal suggesting is you consider whether you want to take this opportunity to upgrade the heating and hot water system in the house to something that is modern and very likely much more comfortable.  If you do then I would recommend you allow yourself time to get some more heat pump quotes, including perhaps from Heat Geek and Octopus, before deciding which to go with, taking advantage of the knowledge and support you will find here.

If you dont want to spend this time then you could just go with either one of the quotes you already have or one from whoever @editor may be able to recommend.  As to the quotes you have, I dont have personal experience of either but Aira is a known quantity and people where appear to have had good experiences, I cant comment on Taggas but others maybe can.  However if you do take this route without a bit more due diligence you may be taking a bit of a risk.

I would encourage you to consider this carefully as, if you do just put in a new boiler, you are missing a great opportunity significantly to upgrade the house, which you wont get again for 20 years.  On the other hand, if you get a badly designed heat pump system, you will regret it.

FWIW I swapped my gas boiler for a heat pump and the house has never been more comfortable.  Running costs are about the same or a bit less (20% less last year, about the same this year) - depending on the ratio of gas to electricity price, which changes from time to time, but the level of comfort and quality of the water system is a revolution.  That's what my wife says BTW, not just me!

I hope that helps, please feel free to ask more questions.

I now see @jamespa has already posted but will still add this to reinforce the point that design and installation quality is more important than brand

@fretless6 — welcome to the forum.

My guess is the executors (may matter who they are, and/or who the beneficiaries are) will want to (and probably legally are required to) do the minimum to protect the value of the estate. That means a gas boiler. But I don't see any reason why you should not persuade them you will pay for an upgrade to a heat pump, for which you should be able to get the BUS grant.  

Posted by: @fretless6

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The Aira guy talked a better talk, but to get the 15 year warranty you've got to pay £19.90 per month for 14 years.

That's not a warranty, that is a piggy bank scheme run by Aria in which they get to keep the principal and the interest, unless something goes wrong. £19.90 x 12 x 14 = £3343.20 plus interest. Better value in my opinion to set up your own building society account.

The general view is that the quality of design and installation is far far far more important that the particular brand of heat pump. Most of the well known brands are generally OK, some have slightly better features, and perhaps a slight price hike for them, but none are immune to failure, and all can be badly installed, sometimes very badly. I'm not aware of any reliable survey on brand reliability, but that said, unless someone can produce evidence to the contrary, I am not aware of any brand that is known to be more unreliable that the others.

But first things first: if you haven't already done so, get a heat loss survey! Or use past gas consumption to get an estimate of heat loss (see posts passim).