SSE but that's the night rate and doesn't look like they'll be giving it to me when I renew next month. Flogas are doing 20c nightrate at the moment though by the looks of it.20 cent a unit including VAT is a great price. Who is your electricity supplier?
How much gas are you using to heat the place currently? How many units? Do you have a modern efficient boiler or an old one?I have asked around my estate but it seems like nobody else has a heat pump to date. Would anyone out there have experience of running a heat pump in a 1970s semi detached? Cheers
How much gas are you using to heat the place currently? How many units? Do you have a modern efficient boiler or an old one?
Heat pumps systems are slower to react, so you can assume the system would need to be on longer, and if the house is as leaky as you suggest, it might struggle to get up to temperature, costing you a fortune in the process.
Thanks for all those details. much appreciated - some quick questions - what sort of house did you retrofit - how old and how big? Also, when you say night rate - is that the rate for electricity used between certain hours or is this something different? CheersSSE but that's the night rate and doesn't look like they'll be giving it to me when I renew next month. Flogas are doing 20c nightrate at the moment though by the looks of it.
Having personally installed hundreds of heat pumps this year alone I can say they are excellent in the right environment.. Everyone seems to be very skeptical about the heat pumps
The house was built around 2000. 400sqm dormer with cavity walls. Insulation levels were already fairly high when we moved in, so it had a B2 BER. By the time it’s finished we’ll have pumped the rest of the cavity in the walls, increased floor insulation in a few rooms where we installed UFH, all passive wall vents removed and a MVHR system installed, all windows/doors replaced with triple glazed, 16kW heatpump installed, work on airtightness following Mick’s advice (downlighters covered, airtight tapes around floor-to-wall joints etc) and some solar PV. BER will be A2 at that point according to the heatpump assessment we had done.Thanks for all those details. much appreciated - some quick questions - what sort of house did you retrofit - how old and how big? Also, when you say night rate - is that the rate for electricity used between certain hours or is this something different? Cheers
The SEAI numbers are a reasonable guide for heat energy costs and they now include heat pumps, see the most recent April data.These are just made up numbers but you get the point.
I’m struggling to understand those tables a bit. Am I reading correctly that a 90% efficient boiler in band D natural gas usage would be €0.1715/kWh? Then for a heatpump in band DD you’re looking at €0.1477/kWh with a 2.5 COP, getting cheaper as your COP improves?The SEAI numbers are a reasonable guide for heat energy costs and they now include heat pumps, see the most recent April data.
Even factoring in heat pump COP, gas is still cheaper.
Thanks, your experience is really helpful. I’ll ring the assessors tomorrow morning and find out more about the air tightness element, it is crazy if this hasn’t been included. I did notice there is s section in the grant application for airtightness but that is blank. I agree with you about getting that work done as part of the package but the problem for me is that the expenditure is already a lot for me so I can’t afford to keep spending more, even when it’s a small amount.The house was built around 2000. 400sqm dormer with cavity walls. Insulation levels were already fairly high when we moved in, so it had a B2 BER. By the time it’s finished we’ll have pumped the rest of the cavity in the walls, increased floor insulation in a few rooms where we installed UFH, all passive wall vents removed and a MVHR system installed, all windows/doors replaced with triple glazed, 16kW heatpump installed, work on airtightness following Mick’s advice (downlighters covered, airtight tapes around floor-to-wall joints etc) and some solar PV. BER will be A2 at that point according to the heatpump assessment we had done.
To Mick’s points above though, I actually think the airtightness work is going to have the biggest impact on comfort in the house, there were huge holes behind some of the skirting that cold air would howl through in the winter. I understand why an airtightness test/assessment is not part of the BER assessment given how many of them need to be conducted to allow house sales etc, but the SEAI not requiring one as part of the heatpump assessment is absolutely crazy. You’re spending maybe €10-20k putting in a heatpump, what’s another few hundred to have the airtightness properly assessed when it is going to have a huge impact on the outcome.
Having said all that, improving the airtightness of your house is unlikely to be much extra work/cost when you’re having so much done anyway. Now that you know you should be doing it, you can just have your contractor to factor it in. An assessment before they start might be useful to identify the problem areas and set a baseline to work from.
Those figures are very interesting so thanks for that, my concern is that I will do the upgrades and then find it’s not enough but at that point there’ll be no going back.There is a myth that Heat Pump can't work in older homes.
A heat pump is just a source of heat. If the system is designed properly it can heat anything (even an uninsulated drafty 1970's house).
The key is to get the heat pump to heat the house at a lower cost than your current heat source. This depends on the cost of the fuel vs the cost of the electricity AND the efficiency of the old system vs the efficiency of the heat pump.
E.g.
Gas Boiler 85% efficient 10c per KWh = 11.76 cent per KWh of heat
Heat Pump 300% efficient 20c per KWh = 6.67 cent per KWh of heat
These are just made up numbers but you get the point. I did some rough calculations that (at a certain price point in time) showed you needed the Heat Pump to be ~260% efficient (COP 2.6) to break even.
In order to get good COP numbers (i.e. high efficiency) from your heat pump you have to run it at low temperatures (i.e. <45oC or better yet 35oC). But in order to heat a large area (or an old uninsulated drafty 1970's house) at low temperatures you need Very BIG radiators.
Of course it makes more sense to 1st upgrade the house because then you need a smaller heat pump and smaller radiators. But it is incorrect to say a heat pump won't work for old houses.
Pretty close. There will also be some loss from the pipework that isn't accounted for in the boiler efficiency rating, varying with the seasons (ambient temperature). They state the methodology they use to calculate that is on their site but I haven't been able to find it. If your pipework is all insulated you could assume that is low.I’m struggling to understand those tables a bit. Am I reading correctly that a 90% efficient boiler in band D natural gas usage would be €0.1715/kWh? Then for a heatpump in band DD you’re looking at €0.1477/kWh with a 2.5 COP, getting cheaper as your COP improves?
So is the data not showing that a heatpump is cheaper than gas?Pretty close. There will also be some loss from the pipework that isn't accounted for in the boiler efficiency rating, varying with the seasons (ambient temperature). They state the methodology they use to calculate that is on their site but I haven't been able to find it. If your pipework is all insulated you could assume that is low.
For heat pumps they maintain a database where you can look up the Seasonal Performance Factor.
Oh, the delivered cost is what I was looking at, but I should have been looking in the other columns!! D'oh!So is the data not showing that a heatpump is cheaper than gas?
Yes, so just to clarify the Data that Leo linked to shows that a heatpump is cheaper than gas.So is the data not showing that a heatpump is cheaper than gas?
Yes, so just to clarify the Data that Leo linked to shows that a heatpump is cheaper than gas.
A 90% efficient Gas boiler would cost 12.8 to 20.3 cent per KWh of heat
A Heat Pump with COP of 3 would cost 10.1 to 17.5 cent per KWh of heat
The devil is in the detail was never more apt than for the questions you are asking... presume nothing!Firstly, sorry for not getting back to this earlier - one of those weeks!
I have to admit those figures were not clear at all to me so thanks @AJAM @Zenith63 and @Leo for looking into all this in such detail and clarifying, very much appreciated.
Just have a few followup questions
1. COP factor, I presume this is the same for everyone but varies according to the temperature outside?
2. Presuming you had a well insulated, airtight house, I take it that a heat pump would be cheaper to run than a gas boiler once you got the initial temperature in the house to an acceptable level?
3. Would you expect that it would take much extra work/much extra disruption if, after adding external insulation and new windows and doors, airtightness turned out to be an issue?
Thanks
Thanks @Micks'rThe devil is in the detail was never more apt than for the questions you are asking... presume nothing!
1. While the external temperature definitely impacts the COP, the design and install can have a much bigger impact, i.e. either a poorly designed or installed heat pump (size, distribution system, control etc) can result in a horrendous COP.
2. You have to do the sums and it depends on the unit price for each energy source combined with the actual system efficiency but generally you should expect that a hp is cheaper to run.
3. Addressing air tightness / ventilation should be central to any fabric upgrade, so thinking about it afterwards is not a great idea and, depending on a number of factors such as house type / layout / build method etc etc, could add significant extra expense / disruption even to the point of undoing some of the recent upgrade works.
If you were home at the time you’d know if it was done, they’d be sealing up all your vents then sealing the front door and using a big blower to try and pressurise the house. It’s not subtleI still have to get back to the company that did the technical assessment to make sure this wasn't included but there is no mention in the report so I presume it wasn't.
If you were home at the time you’d know if it was done, they’d be sealing up all your vents then sealing the front door and using a big blower to try and pressurise the house. It’s not subtle. But if it was the standard SEAI assessment then it would not have been done.
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