Off-Peak Smart metering

Scot_39

QrizB said:

WiserMiser said:

One point often overlooked is that the real cost of a heat pump is extremely high. The £7500 government grant may make it seem relatively affordable (don't forget to oversize the radiators) but when it expires after 10 years or whatever you'll be hit with the full cost of renewal.

Renewing a heat pump (replacing one in an existing system) shouldn't be all that much more expensive than replacing a gas boiler.

Here's a Worcester Bosch boiler  - £1412.

And an 8kW Samsung heat pump - £1910.

The difference is £500.

There must be a lot of homes need a lot of extra work when getting an ASHP then

As Octopus say there average cost - is c£4500 over the BUS grant - so £12,000 total.

EOn average ... start (whatever that means) - £11000.

Say in a three bed semi modern home - how much would it cost to replace boiler and all radiators with larger ones and new piping throughout - for instance - vs those type of ASHP all in figures ?

WiserMiser

QrizB said:

WiserMiser said:

One point often overlooked is that the real cost of a heat pump is extremely high. The £7500 government grant may make it seem relatively affordable (don't forget to oversize the radiators) but when it expires after 10 years or whatever you'll be hit with the full cost of renewal.

Renewing a heat pump (replacing one in an existing system) shouldn't be all that much more expensive than replacing a gas boiler.

Here's a Worcester Bosch boiler  - £1412.

And an 8kW Samsung heat pump - £1910.

The difference is £500.

Not comparing like with like.

The boiler has a respectable output of 24kW.  The heat pump has a tiddly output of just 8kW.  Might suit a small  bedsit !

Scot_39

WiserMiser said:

QrizB said:

WiserMiser said:

One point often overlooked is that the real cost of a heat pump is extremely high. The £7500 government grant may make it seem relatively affordable (don't forget to oversize the radiators) but when it expires after 10 years or whatever you'll be hit with the full cost of renewal.

Renewing a heat pump (replacing one in an existing system) shouldn't be all that much more expensive than replacing a gas boiler.

Here's a Worcester Bosch boiler  - £1412.

And an 8kW Samsung heat pump - £1910.

The difference is £500.

Not comparing like with like.

The boiler has a respectable output of 24kW.  The heat pump has a tiddly output of just 8kW.  Might suit a small  bedsit !

The two arent designed to match peak powers.

And a gas ch boiler will  will typically be derating to a fraction of its peak within 1/2 hr to 1hr from cold.  And even then power cycling within an hour or so.

The radiators limiting the power delivery to the home, not the boilers.

In a 2 bed home you might be only driving say 6 rads with effective power of 0.5 kW - 2 kW in a larger living room.  Maybe say 10kW total output at delta t50 - so flow temps 65-70 degrees say  - most now run colder to save.

You want more like delta t 15-25 to run an ashp at high cops flow temps 35-45 say -- rooms 15-20C say halving that affective power or more. So just 5kW or below out even with potentially bigger and /or or double radiators replacing singles etc 

So yes tge ashp will take longer to heat from cold but it will over a day be more than capable.

Put the ashp on 1/2 to 1 hr earlier than the gch - and tge home will likely be as toasty as required.



Run an ashp say it off peak only on say Cosy tou 8hrs if can run for full 8hrs - dubious if would - given effective radiator powers - but upto 64kWh - again more than enough for hw and heating for most small homes. 

Even half that 32kWh would likely be enough for most modern efficient homes.

Ps if you want tiddly try nsh.  My 3 are rated 7kW in - c2kW max total.  I use about 12-15kWh for my space hesting on average winter dsys - but over double that on sub zero days - 12kWh in over 24 hrs output = average 0.5kW power.

Even 4 kW - half thst 8kW plenty by comparison.

QrizB

WiserMiser said:

QrizB said:

WiserMiser said:

One point often overlooked is that the real cost of a heat pump is extremely high. The £7500 government grant may make it seem relatively affordable (don't forget to oversize the radiators) but when it expires after 10 years or whatever you'll be hit with the full cost of renewal.

Renewing a heat pump (replacing one in an existing system) shouldn't be all that much more expensive than replacing a gas boiler.

Here's a Worcester Bosch boiler  - £1412.

And an 8kW Samsung heat pump - £1910.

The difference is £500.

Not comparing like with like.

The boiler has a respectable output of 24kW.  The heat pump has a tiddly output of just 8kW.  Might suit a small  bedsit !

8kW is plenty for a typical 3-bed semi. I think @matt_drummer 's heat pump is that sort of size?

Scot_39 said:

In a 2 bed home you might be only driving say 6 rads with effective power of 0.5 kW - 2 kW in a larger living room.  Maybe say 10kW total output at delta t50 - so flow temps 65-70 degrees say  - most now run colder to save. 

In my case - 1950s three-bed semi - the total nominal power of my radiators at 70C flow temperature is ca. 10kW. I run a ~55C flow temp which reduces the output to ca. 6kW per the table here:

https://www.stelradprofessional.com/stelrad-correction-factor/

In practice my gas use peaks at about 60 kWh a day, (which includes hot water and cooking) which would suggest my heat loss is closer to 2kW.

An 8kW heat pump could easily be too big.

Scot_39 said

There must be a lot of homes need a lot of extra work when getting an ASHP then

...Say in a three bed semi modern home - how much would it cost to replace boiler and all radiators with larger ones and new piping throughout - for instance - vs those type of ASHP all in figures ?

Costs above and beyond the heat pump itself are currently being discussed in this thread:

https://forums.moneysavingexpert.com/discussion/6628652/ashp-quotes/p1

matt_drummer

My heat pump is 8kW @QrizB and it is bigger than I need with a maximum daily requirement of 120kWh of heat for heating and DHW.

I do run the house quite warm though, between 22c and 24c most of the time.

I have about 50kW of radiator capacity at delta T of 50c (the nominal 70c mean flow temperature and 20c room temperature).

Those radiators allow me to run the heat pump at 30c flow temperature when it is 5c outside and 22c indoors with a delta T between mean flow temperature and room temperature of only 5 or 6c.

The initial cost of installing a heat pump is high, but it is a one off cost.

When comparing replacing a gas or oil boiler the heat pump is always going to be more costly but not so different from installing and oil or gas system from scratch.

Replacing a heat pump once installed is a very simple job, pretty much DIY and can be done in just a few hours and likely cheaper than replacing a gas or oil boiler.