RomyD Posted November 12, 2021 Share Posted November 12, 2021 Is it fair to think of storage heaters and immersion heaters as having an economic efficiency of about 200%? (Depending on the supplier tarrif). Whatever the outside temperature. Assuming the heaters will still produce heat into the evening which I think a correctly sized system ought to these days. Has anyone done say a twenty year cost benefit of ashp Vs good old fashioned e7 based storage and immersion heat? Link to comment Share on other sites More sharing options...
Temp Posted November 12, 2021 Share Posted November 12, 2021 I once had a house with storage heaters that were made about 1995. They leaked too much heat. In the spring and autumn you needed to put heat into them "just in case" it was going to be cold next day. If it wasn't as cold as you expected the room would overheat even with them shut off. Ended up ripping them out and fitting gas boiler and rads. 1 Link to comment Share on other sites More sharing options...
Nickfromwales Posted November 12, 2021 Share Posted November 12, 2021 Cost benefit is one thing. My 2 cents is who would want these things in this day and age? Coarse and indiscriminate and usually throw the majority of their heat out when you don't want it, and have little useful sustain for when you do. For the size of footprint, larger radiators with an ASHP is a no-brainer, sorry. CoP of 2.5-3 should be reasonable, so not far off the cost of natural gas to run, or less in off-peak periods. Link to comment Share on other sites More sharing options...
RomyD Posted November 12, 2021 Author Share Posted November 12, 2021 1 hour ago, Temp said: I once had a house with storage heaters that were made about 1995. They leaked too much heat. I too had a very small house in the early 90s, two up two down type of thing. It was our first place and had a single woefully inadequate storage heater. I wonder how it might have performed had it simply been a bit bigger, but the real problem back then was it was simply a terribly inefficient building. 1 hour ago, Nickfromwales said: For the size of footprint, larger radiators with an ASHP is a no-brainer, sorry. CoP of 2.5-3 should be reasonable, so not far off the cost of natural gas to run, or less in off-peak periods. It's not a no brainer in my mind. The cost to run it is only part of the story isn't it? Up front capital cost without any subsidy at all for many, is now much more relevant than before, especially if you don't have any radiators to start with. Link to comment Share on other sites More sharing options...
Iceverge Posted November 13, 2021 Share Posted November 13, 2021 Quick sums. DHW 3000 kWh + Heating 6000kWh/annum. Storage heaters + immersion £2000 upfront. E7 @18p per kWh. 20 year cost £34400 ASHP COP of 3 for DHW and COP of 4 for Heating Electricity at 22p/kWh to account for some day heating. ASHP + UFH initial outlay £11000 20 year cost £23000 Cost of £10000 credit over 20 years @2.2% = £2400 Total £24400 ASHP cheaper by £10k over 20years. 1 Link to comment Share on other sites More sharing options...
SteamyTea Posted November 13, 2021 Share Posted November 13, 2021 5 hours ago, Iceverge said: E7 @18p per kWh. I pay 12p 5 hours ago, Iceverge said: Electricity at 22p/kWh to account for some day heating. I pay 24p So E7 23,600 ASHP 25,400 The only maintenance I have had in my 34 year system is a new DHW cylinder, 200 quid. The 'overheating' during the day and the 'no heat when you need it' is just management. Just as we tell people that ASHP systems are not like gas, E7 with storage heaters are also not like gas. Link to comment Share on other sites More sharing options...
RomyD Posted November 13, 2021 Author Share Posted November 13, 2021 7 hours ago, Iceverge said: Quick sums. DHW 3000 kWh + Heating 6000kWh/annum. Storage heaters + immersion £2000 upfront. E7 @18p per kWh. 20 year cost £34400 ASHP COP of 3 for DHW and COP of 4 for Heating Electricity at 22p/kWh to account for some day heating. ASHP + UFH initial outlay £11000 20 year cost £23000 Cost of £10000 credit over 20 years @2.2% = £2400 Total £24400 ASHP cheaper by £10k over 20years. Storage If I put the leccy price I have been quoted into your sums for storage I get: E7 13p System £2000 Total £25,400 For ASHP I get: Assuming your leccy costs Pump and UFH, £22k as I have been quoted 20yr cost £34k If was able to invest the cap cost difference I could earn; Loss of investment return on £20k, 2.2% @20years, £11k Total ignoring investment loss £34k Total Inc investment losses £45k So ASHP over 20years comes out at around £8600 more best case or £19600 more with a modestly performing investment. Even using 18p for e7 storage heating so 20yr at £34400 gives an ASHP saving of just £400 with the higher cap costs but that ignores potential investment returns of £11k so still £10k worse. Conclusion: Get storage heaters and stick the savings into you pension pot and unless your retired you'll get 20% tax relief, maybe 40% too. Just thinking out loud really and I am not a financial advisor and this is not financial advice! Link to comment Share on other sites More sharing options...
Iceverge Posted November 13, 2021 Share Posted November 13, 2021 It really is a piece of string question. Totally dependent on projected electric prices,(I used octopus energy new tariffs) cost of initial set up (I ballparked a figure based on another buildhubber) cost of servicing (assumed it was the same as an e7 cylinder). Lifespan of the ASHP(assumed it would last as long as the cylinder) and interest rates (assumed 2.2%) and energy usage. Within these variables it isn't difficult to come up with a multitude of correct answers. Have you considered an A2A setup or an EAHP. About 2k each plus install. Link to comment Share on other sites More sharing options...
SteamyTea Posted November 13, 2021 Share Posted November 13, 2021 18 minutes ago, Iceverge said: Totally dependent on projected electric prices To a certain extent we know what they will be because of the strike prices. So wind us around £60, nuclear £100. Also, if you look at historical prices in the developed world, energy prices are about 5% of household income. There is no reason to think that electricity will have a higher increase rate than anything else. Link to comment Share on other sites More sharing options...
RomyD Posted November 13, 2021 Author Share Posted November 13, 2021 (edited) I think you are right about the string thing. Each case has its own upsides/downsides but I think its useful to use the storage heating costs as a baseline for comparison. Its a simple sum. Anything to do with heat pumps gets harder to work out and I think the equation and debate has been distorted by RHI. If you can get someone else to pay for your system over a few years of course its a no brainer but those days have gone away. A2A sounds interesting but isn't EAHP much the same as MVHR? No gas where we are so has to be electric or oil, or biomass etc. Edited November 13, 2021 by RomyD Link to comment Share on other sites More sharing options...
Iceverge Posted November 13, 2021 Share Posted November 13, 2021 (edited) Sorry I was referring to EAHP for DHW like @Thedreamer uses. For what it's worth I did endless calculations on this for our passive house, over 25 years. (3650kWh/annum DHW and 2650kWh Space heat predicted). A2A HP and E7 cylinder supplemented by solar PV was the best theoretical option but only marginally ahead of an ASHP. The trouble with the ASHP was that although it has the lowest running costs the initial price was too high. It would have needed to work without fault for almost the full quarter of a century to justify the cost. I didn't think this was realistic. With higher heating requirements it would have paid back sooner. At the moment we have E7 and a cheap electric rad. I'm tracking the real energy usage to decide on the best option. Edited November 13, 2021 by Iceverge Link to comment Share on other sites More sharing options...
SteamyTea Posted November 13, 2021 Share Posted November 13, 2021 2 minutes ago, Iceverge said: quarter of a decade Don't you mean century. Which in my experience, is what E7 kit easily lasts (I am in a soft water region). Link to comment Share on other sites More sharing options...
Iceverge Posted November 13, 2021 Share Posted November 13, 2021 I did. Edited ta Link to comment Share on other sites More sharing options...
SimonD Posted November 13, 2021 Share Posted November 13, 2021 4 hours ago, RomyD said: A2A sounds interesting Definitely worth a look for space heating. You will usually get a much better COP than A2W (up to 4.6) and the latest life cycle assessment I read said A2A gave a 34% reduction in carbon emmissions over A2W. The only limitation can be the max number of indoor units for a multi-split system. You'd also get handy cooling as they're usually sold as air-conditioners with heating capability. Link to comment Share on other sites More sharing options...
RomyD Posted November 13, 2021 Author Share Posted November 13, 2021 Having had a google fest this afternoon, those A2A multi split multi room systems look really interesting. Could be the perfect solution for us. Link to comment Share on other sites More sharing options...
Mr Punter Posted November 13, 2021 Share Posted November 13, 2021 I have some small flats and would be interested in the A2A units to improve the EPC rating, but I don't think they appear in SAP. Link to comment Share on other sites More sharing options...
SimonD Posted November 13, 2021 Share Posted November 13, 2021 (edited) 1 hour ago, Mr Punter said: I have some small flats and would be interested in the A2A units to improve the EPC rating, but I don't think they appear in SAP. SAP is a total mess on this one. I found a document somewhere from the government on the methodology, which also relates to grants and RHI whereby it said they're excluded because they provide cooling. Apparently the system needs to be heat only. However, there seems to be a bit of oversight in that A2W can also provide cooling, but its main purpose is heating ?. Would be interesting to find out if any of the manufacturers are prepared at any point to try and get their systems added to the database and if there are any specific models on there. Edited November 13, 2021 by SimonD Link to comment Share on other sites More sharing options...
SteamyTea Posted November 13, 2021 Share Posted November 13, 2021 1 hour ago, SimonD said: Would be interesting to find out if any of the manufacturers are prepared at any point to try and get their systems added to the database and if there are any specific models on there. I think with regards to the old RHI, they decided that they were cheap enough not to need subsidising. Fir a lot of places, they would be a viable heating system. 1 Link to comment Share on other sites More sharing options...
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