Heat Pump Questions

Verdigris

I'm just saying that the price of mains gas may well be the same as LPG in a year or so. Why wouldn't they be? They're the same thing, essentially. In fact a good proportion of mains gas is LNG brought in from the Middle East, or was until the Chinese outbid us.

QrizB

Telegraph_Sam said:

[I think that there was a further post to this thread from OrizB that appears to have been removed]

The benefits of more efficient radiators, better insulation etc are indisputable. But to revert to my original question: Putting it crudely what have these got to do with the type of heating? Better draught proofing etc will benefit my heating costs regardless of whether I have a gas combi or an ASHP (or a ground source pump?)
To calculate the advantages of heat pumps the ambient conditions must be identical. The impression I get is that to some degree heat pumps are more sensitive to temperature changes (so in that specific sense only they "need" better insulation). My gut feel is that one can spend a lot of money in switching to heat pumps in return for unspecified gains.

Apologies, I deleted my reply as being off-topic.

Gas boilers are pretty insensitive to settings. OK at their best they might be 90% efficient, and at their worst maybe 60%, but from one extreme to the other that's only a 50% increase in the input energy needed. With gas at 4p/kWh that's the difference between paying 4.4p for a kWh of useful heat and paying 6.7p (for 10,000kWh, £440 to £670). (Don't ignore this, it's still worth adjusting your settings to keep the efficiency up.)

Heat pumps are much more finicky. They can vary from 500% efficient (or more) to 150% efficient (or less). With electricity at 20p/kWh that's a range of 4p to 13p for the same heat output (for 10,000kWh, from £400 to £1300). If you look at page 98 (marked A-94) of this Mitsubishi pdf you can see some real manufacturer data showing the relationship between water flow temperature, outdoor temperature and performance.

Telegraph_Sam

These are what-if scenarios which require accurate crystal ball technology.  I am trying to gauge what the advantages of a heat pump would be as things stand at present or in the very near future.

Edit: this relates to the last but  one post.

Reed_Richards

Telegraph_Sam said:

The benefits of more efficient radiators...

There's not really any such thing as a more efficient radiator.  You can make radiators more efficient per unit volume by increasing their effective surface area and even more efficient still per unit volume by using an electric fan to blow air over/through them.  But the benefit you achieve is really space-saving, not efficiency

Telegraph_Sam said:

The benefits of ... better insulation etc are indisputable. But to revert to my original question: Putting it crudely what have these got to do with the type of heating? Better draught proofing etc will benefit my heating costs regardless of whether I have a gas combi or an ASHP (or a ground source pump?)

Yes, that's it exactly; you've got it at last!  Better insulation will benefit any type of heating.

 Telegraph_Sam said:

My gut feel is that one can spend a lot of money in switching to heat pumps in return for unspecified gains.

 Unquantified gains certainly.  But a simple rule of thumb is that an ASHP, in the UK and properly installed should use about 1/3 of the energy you would otherwise need to heat your dwelling and hot water. 

Telegraph_Sam

"But a simple rule of thumb is that an ASHP, in the UK and properly installed should use about 1/3 of the energy you would otherwise need to heat your dwelling and hot water"
.... provided that the ambient temperature stays within a certain range otherwise the savings are reduced or eliminated??

Verdigris

Get a ground-source heat pump if you want the same COP all year round.

Telegraph_Sam

Thanks but I am trying to make things simple! I suspect that GSHP's come with  a can of complications all of their own.

It would be as a separate topic interesting to compare the two types of heat pump, pros and cons, and know if one is more competitive, all things considered,  with gas combis than the other. But I fear that such triangular cost and performance comparisons could get really complicated.

Verdigris

Telegraph_Sam said:

These are what-if scenarios which require accurate crystal ball technology.  I am trying to gauge what the advantages of a heat pump would be as things stand at present or in the very near future.

Edit: this relates to the last but  one post.

So, do you not take future scenarios into account when, say, choosing what car to buy and what fuel option would be most cost-effective?

[Deleted User]

Telegraph_Sam said:

 I am trying to gauge what the advantages of a heat pump would be as things stand at present or in the very near future.

As the originator of this thread I still feel that I know that IF I had to replace my current Gas boiler today (or even in the next year or so) the economic reasons for me personally doing this are dubious especially when I consider the extra cost of probably replacing all my current micro bore CH piping, fitting an extra hot water cylinder and possibly many of the rads etc.  OK there are climate change considerations here as well but I'm just not sure how much I can or would dig into my pocket to assuage the GT's of this world.  Maybe in a few years time (before say 2030) things will be more clear cut for the dinosaurs like me who love the more or less instant heat, convenience and current cost or heating provided by a gas boiler.        

Verdigris

I think a year from now the numbers will look significantly different. However, I don't think there is a good case to rip out perfectly serviceable gas systems. Just replace them when they reach the end of their natural lives.