Should I or Shouldn't I ASHP?

[Johnnyt]

Happy new year to all.

 

I have a EPC A rated 3 year old property with ground floor of 160 sq m and ufh. Additionally have towel rads 3 of and 4 first floor rads.

Presently I have a Viessmann w200  27kW system boiler range rated to 11kW running at flow temp of 33c with a deltaT of 5 to 6c at the boiler.

It also feeds a 500l high gain uvc, 3 sq m coil.

My boiler is only 3 years old and all is functioning swimmingly. My heat loss measured during Dec is about 4 to 4.5kW.

Additionally I have 14.8 kWp of PV and 30 kWh or storage.

I appear to be system ready for an ASHP but the newness of the boiler and its functionality is holding me back from changing.

last years gas usage, space and dhw was 14300kWh. I used 6.4 mWh of electricity and exported 11mWh at 15p a kWh.

 

What would you do?

 

 

[JohnMo]

I migrated from boiler to ASHP, mainly to do cooling, then ran it hybrid in winter, with gas boiler. Reason, heating with ASHP in mild weather is so much cheaper than gas. Did the sums after a year in hybrid mode and realised the boiler was actually costing me over a £100 each year, just having it connected. It also saved nothing in energy terms. Now full time ASHP and no gas, have left the gas boiler in place, and if required I could always have the meter reinstated.

 

But my ASHP is oversized, so am actually looking to replace with a smaller one.

Edited 7 hours ago by JohnMo

[MrPotts]

I would keep the boiler until it reaches end of life.

Edited 7 hours ago by MrPotts

[Dillsue]

2 hours ago, Johnnyt said:

I appear to be system ready for an ASHP but the newness of the boiler and its functionality is holding me back from changing.

 

What would you do?

 

 

If youve got a near new working system then your primary motivation for change is likely only for environmental reasons?? If your boiler is still running perfectly in 20 years time that would be an awful lot of carbon emitted that you could have avoided if you'd made the change now.

 

I'd bin the boiler now but my measure of ROI isn't just £££. Only you know your measure of ROI.

[JohnMo]

There are plenty of really good performance ASHP out there now. They don't cost a fortune either. Around £2500 is about all you need to spend, get through the grant while they are still about, or self install. You already have the cylinder, so a small amount of plumbing changes, a bit of electrical work, job done. Tell your gas supplier to take meter away.

[Gone West]

5 minutes ago, JohnMo said:

get through the grant while they are still about

This could be true!

 

https://www.independent.co.uk/news/uk/politics/ed-miliband-warm-homes-solar-power-energy-bills-b2892047.html

 

 

[G and J]

If we could do a calculation to determine the total carbon footprint of option a - keep the gas boiler till it dies then replace with latest tech, presumably upgraded heat pump, vs option b - bin the gas boiler and replace immediately with today’s heat pump, I’d be shocked if option a cost the planet less due to the wasted resources out into the boiler.  
 

I’m dead keen on renewables.  We even paid a daft amount to have gas removed from site.   But it’s easy when it’s effectively a blank sheet.  
 

Sadly such an analysis would be so affected by multiple assumptions that it would be hard to believe in it.  But gut feel says your wasting the planet and your own money replacing newish kit now.  But who can really know?

[Iceverge]

3 hours ago, Johnnyt said:

Happy new year to all.

 

I have a EPC A rated 3 year old property with ground floor of 160 sq m and ufh. Additionally have towel rads 3 of and 4 first floor rads.

Presently I have a Viessmann w200  27kW system boiler range rated to 11kW running at flow temp of 33c with a deltaT of 5 to 6c at the boiler.

It also feeds a 500l high gain uvc, 3 sq m coil.

My boiler is only 3 years old and all is functioning swimmingly. My heat loss measured during Dec is about 4 to 4.5kW.

Additionally I have 14.8 kWp of PV and 30 kWh or storage.

I appear to be system ready for an ASHP but the newness of the boiler and its functionality is holding me back from changing.

last years gas usage, space and dhw was 14300kWh. I used 6.4 mWh of electricity and exported 11mWh at 15p a kWh.

 

What would you do?

 

 

 

Can you get an accurate split for your DHW vs Space heating? 

 

What are your motivations, cost or environmental or tinkering?! All are valid but it might help to frame an answer. 

 

Have you considered an ASHP to do "baseload" heating and "free" cooling in summer on PV? It might tick all 3 boxes. 

 

 

 

 

[marshian]

I’d stick with the boiler until end of life (or close to it) just from an environmental perspective (not replacing something that is still functional and effectively a very bloody good and efficient boiler

[DamonHD]

If the embedded carbon/energy is a concern (and generally I don't suspect that it is for machines of this level of complexity), couldn't you gift it to a local gas spares place or GasSafe person for parts?  When my combi was stripped out I did just that with the rather expensive heat exchanger that I'd put in just a year before, and the man was very happy.

 

The sooner people switch to ASHPs and stop directly adding several tonnes per year of CO2 to the atmosphere via the flue, the better.

[Oz07]

Keep till the boiler packs up. Likely 10+ years. 

[Dillsue]

1 hour ago, G and J said:

If we could do a calculation to determine the total carbon footprint of option a - keep the gas boiler till it dies then replace with latest tech, presumably upgraded heat pump, vs option b - bin the gas boiler and replace immediately with today’s heat pump, I’d be shocked if option a cost the planet less due to the wasted resources out into the boiler.  
 

I’m dead keen on renewables.  We even paid a daft amount to have gas removed from site.   But it’s easy when it’s effectively a blank sheet.  
 

Sadly such an analysis would be so affected by multiple assumptions that it would be hard to believe in it.  But gut feel says your wasting the planet and your own money replacing newish kit now.  But who can really know?

From a quick peak at Google gives the following-

14300 kwh of gas@0.18kg co2/kwh gives 2574kg carbon per year currently

14300 kwh from HP at COP 4 uses 3575 kwh grid eleccy@0.177kg co2/kwh which gives 632kg carbon per year with HP. Google suggests  200-400kg of embodied carbon in boiler manufacturer and install.

 

Assuming HP embodied carbon is the same as a boiler then first year of scrapping boiler and installing HP gives 632+300(boiler)+300(HP)=1232kg co2 for new HP versus 2574kg co2 continuing with gas boiler. Half the emissions in year 1 by switching to HP now.

Second and subsequent years is 632kg co2 for HP versus 2574kg co2 continuing with gas boiler. Quarter the emissions in future years after switching to HP.

 

More than happy to have these calcs challenged but seems that moving to a HP beats sticking with a gas boiler from an emissions perspective. OP has significant PV and storage which would likely lower the HP emissions further??

[JohnMo]

4 minutes ago, Dillsue said:

From a quick peak at Google gives the following-

14300 kwh of gas@0.18kg co2/kwh gives 2574kg carbon per year currently

14300 kwh from HP at COP 4 uses 3575 kwh grid eleccy@0.177kg co2/kwh which gives 632kg carbon per year with HP. Google suggests  200-400kg of embodied carbon in boiler manufacturer and install.

 

Assuming HP embodied carbon is the same as a boiler then first year of scrapping boiler and installing HP gives 632+300(boiler)+300(HP)=1232kg co2 for new HP versus 2574kg co2 continuing with gas boiler. Half the emissions in year 1 by switching to HP now.

Second and subsequent years is 632kg co2 for HP versus 2574kg co2 continuing with gas boiler. Quarter the emissions in future years after switching to HP.

 

More than happy to have these calcs challenged but seems that moving to a HP beats sticking with a gas boiler from an emissions perspective. OP has significant PV and storage which would likely lower the HP emissions further??

Sounds about right, plus you delete a standing charge, so win win. 

[SimonD]

1 hour ago, Dillsue said:

Assuming HP embodied carbon is the same as a boiler

 

It's much more than for a gas boiler. There's virtually nothing in a gas boiler, even a system boiler - gas valve, fan, heat exchanger, circulation pump and pcb with some wiring. Plus it's far less volume and weight. A heat pump, lets say with the output required for the OP at about 5kW for arguments sake will weigh nearly 3x the boiler and have about 3x the packaged volume. From a manufacturing perspective it's far more complex.

 

But over its lifetime the heat pump will produce much, much less especailly as the grid continues to decarbonise. For example, this article: https://les.mitsubishielectric.co.uk/the-hub/carbon-embodied-operational-and-whole-life-cycle 

[Roger440]

6 hours ago, Johnnyt said:

Happy new year to all.

 

I have a EPC A rated 3 year old property with ground floor of 160 sq m and ufh. Additionally have towel rads 3 of and 4 first floor rads.

Presently I have a Viessmann w200  27kW system boiler range rated to 11kW running at flow temp of 33c with a deltaT of 5 to 6c at the boiler.

It also feeds a 500l high gain uvc, 3 sq m coil.

My boiler is only 3 years old and all is functioning swimmingly. My heat loss measured during Dec is about 4 to 4.5kW.

Additionally I have 14.8 kWp of PV and 30 kWh or storage.

I appear to be system ready for an ASHP but the newness of the boiler and its functionality is holding me back from changing.

last years gas usage, space and dhw was 14300kWh. I used 6.4 mWh of electricity and exported 11mWh at 15p a kWh.

 

What would you do?

 

 

 

As others have said, you have not indicated your motivations. So rather a difficult question to answer.

 

As you ask, id just leave it until it breaks. Put the money you would have spent to good use elsewhere.

[Roger440]

4 hours ago, Gone West said:

This could be true!

 

https://www.independent.co.uk/news/uk/politics/ed-miliband-warm-homes-solar-power-energy-bills-b2892047.html

 

 

 

Ed on another tangent. 

 

So, Rachel says they are getting rid of the ECO4 scheme to reduce bills, and Ed says he is going to load gas with extra cost and increase them. Left hand and right hand and all that.

 

Not that it stacks up anyway, as 13bn, is less than £500 per household. Thats not going to buy you much, and certainly not at grossly inflated grant harvesting prices. Maybe it just for labour party members or some other select group? 

[Johnnyt]

Here’s the stats for the boiler space heating vs DHW

 

Measured at the boiler and it aligns with actual usage measured by Octopus.

My other worry at a change would be how low the ASHP could modulate.

We are in winter but although mild (ish) as my boiler does down to 2250kW at a COP of 4 the ASHP would have to go down to 560 watts.

The boiler stays at minimum modulation for a while, today it has run continuously for over 15 hours and counting, modulating of course.

What decent ASHP at say 7kW can get so low. It would be even more salient as thing starts to warm up to prevent cycling.

[Johnnyt]

I guess to some extent it is to do my bit for the environment.

As a money saving exercise, it is probably futile.

Curiosity is also a factor and as is future proofing.