ᐅ Is the additional cost of an air-to-water heat pump compared to gas justified?
Created on: 13 Feb 2022 14:20
S
SoL
Hello everyone,
I could use your advice on choosing a heating system. We (2 adults, 4 children) are currently in talks with a general contractor (GC) about a house, and so far it sounds pretty good. The scope of work is acceptable. We are not aiming for a specific KfW energy standard but expect to land somewhere between 70 and 55. The heating load calculation is not finished yet since the contract is not signed.
The GC’s standard offer includes the following:
Gas heating: Vaillant auroCOMPACT VSC S 206/4-5 190 condensing compact unit
Rated at 20 kW (wow, why?)
Includes a 190 L (50 gallons) hot water storage tank, plus 2.5 m² (27 ft²) of solar thermal collectors as a package.
Alternatively, he offers an air-to-water heat pump as a substitute for the gas heating and solar thermal system:
Thermia iTec Plus with 9 kW output, cooling function, and a 300 L (79 gallons) hot water storage tank alongside.
I would actually prefer to go with the heat pump, but:
The additional cost for the heat pump solution is a hefty €8,100. For that, we wouldn't need a gas connection...
Maybe I’m mistaken or the math doesn’t add up, but does it really pay off to choose the heat pump?
Even if you achieve a COP of 3.5 or 4, the extra cost of €8,100 minus €2,500 for the gas connection = €5,600 would only pay off very, very late.
At €0.30 per kWh electricity and 10,000 kWh annual consumption with a COP of 4, the cost would be €750. At a gas price of €0.10, the cost would be €1,000. So the difference is €250 per year, meaning the extra cost (ignoring the solar thermal system) would only amortize after 22 years.
Is that correct, or am I missing something / making an error in the calculation? Given the additional cost, I am leaning towards gas, possibly with an extra hot water storage tank.
Thanks and best regards
SoL
I could use your advice on choosing a heating system. We (2 adults, 4 children) are currently in talks with a general contractor (GC) about a house, and so far it sounds pretty good. The scope of work is acceptable. We are not aiming for a specific KfW energy standard but expect to land somewhere between 70 and 55. The heating load calculation is not finished yet since the contract is not signed.
The GC’s standard offer includes the following:
Gas heating: Vaillant auroCOMPACT VSC S 206/4-5 190 condensing compact unit
Rated at 20 kW (wow, why?)
Includes a 190 L (50 gallons) hot water storage tank, plus 2.5 m² (27 ft²) of solar thermal collectors as a package.
Alternatively, he offers an air-to-water heat pump as a substitute for the gas heating and solar thermal system:
Thermia iTec Plus with 9 kW output, cooling function, and a 300 L (79 gallons) hot water storage tank alongside.
I would actually prefer to go with the heat pump, but:
The additional cost for the heat pump solution is a hefty €8,100. For that, we wouldn't need a gas connection...
Maybe I’m mistaken or the math doesn’t add up, but does it really pay off to choose the heat pump?
Even if you achieve a COP of 3.5 or 4, the extra cost of €8,100 minus €2,500 for the gas connection = €5,600 would only pay off very, very late.
At €0.30 per kWh electricity and 10,000 kWh annual consumption with a COP of 4, the cost would be €750. At a gas price of €0.10, the cost would be €1,000. So the difference is €250 per year, meaning the extra cost (ignoring the solar thermal system) would only amortize after 22 years.
Is that correct, or am I missing something / making an error in the calculation? Given the additional cost, I am leaning towards gas, possibly with an extra hot water storage tank.
Thanks and best regards
SoL
Hangman schrieb:
What about the cooling function? Do you need or want it? If not, can it be left out? That refers to an additional expansion valve in the system. It is part of the standard equipment on many heat pumps. Removing it is usually not really possible once installed. However, if it’s not included initially and the client requests it later, it can sometimes cost four-digit sums.
Hangman schrieb:
What about the cooling function? Do you need or want it? If not, can it be left out? For us, it’s secondary. It can probably cool in summer, but supposedly only about 2°C (3.6°F) below room temperature after initial startup.
We are leaving it out of the decision.
I don’t think the general contractor doesn’t want the heat pump, because it was simply included in the first contract draft and the sales team is actively promoting it...
I think this is more a sign of a seller’s market, expecting the first offer to be signed blindly 🙄
The seller's market exists regardless of the heating system. Why is the additional cost for a heat pump so high — in the sense of being too high? What exactly is included in the heat pump option? Which parts of it could be omitted (e.g., ERR, buffer tank, cooling function)? You should question that.
Hello,
the additional cost is indeed quite high. Or is it possible that the gas boiler was calculated with standard radiators, while the heat pump includes an "upgrade" to underfloor heating?
But your calculation is basically correct. When you look at it realistically, the heat pump is still at a disadvantage for now. No one can say how this will develop in the long term.
We also decided on gas. However, make sure to design the underfloor heating so that you can install a heat pump later on. That means the pipe spacing needs to be small enough to allow for low supply temperatures. The gas heating system won’t last forever—after about 20 years you’ll have to replace it, and then it’s very likely you won’t be allowed to install a gas heating system anymore.
Regarding the 20 kW peak output: you don’t need that for heating, but for domestic hot water production. And with four children, you will definitely need it! For a heat pump, a 300-liter (80-gallon) hot water tank might be too small in some cases. If six people want to shower in the morning, the last one might end up with only cold water.
The gas boiler can reheate the water almost on demand with its 20 kW output.
Best regards,
Andreas
the additional cost is indeed quite high. Or is it possible that the gas boiler was calculated with standard radiators, while the heat pump includes an "upgrade" to underfloor heating?
But your calculation is basically correct. When you look at it realistically, the heat pump is still at a disadvantage for now. No one can say how this will develop in the long term.
We also decided on gas. However, make sure to design the underfloor heating so that you can install a heat pump later on. That means the pipe spacing needs to be small enough to allow for low supply temperatures. The gas heating system won’t last forever—after about 20 years you’ll have to replace it, and then it’s very likely you won’t be allowed to install a gas heating system anymore.
Regarding the 20 kW peak output: you don’t need that for heating, but for domestic hot water production. And with four children, you will definitely need it! For a heat pump, a 300-liter (80-gallon) hot water tank might be too small in some cases. If six people want to shower in the morning, the last one might end up with only cold water.
The gas boiler can reheate the water almost on demand with its 20 kW output.
Best regards,
Andreas
Thanks to everyone who quickly provided so many ideas!
The underfloor heating will be installed regardless and is always designed to allow for low supply temperatures.
I am clearly leaning towards gas and will try to accommodate the additional special requests while keeping in mind the previous prices for the air-to-water heat pump and also the plaster with a light reflectance value below 30, limiting them to very few.
The prices really shock me... But happy wife, happy life, so some things will probably still be included... :p
The underfloor heating will be installed regardless and is always designed to allow for low supply temperatures.
I am clearly leaning towards gas and will try to accommodate the additional special requests while keeping in mind the previous prices for the air-to-water heat pump and also the plaster with a light reflectance value below 30, limiting them to very few.
The prices really shock me... But happy wife, happy life, so some things will probably still be included... :p
We have now completed the first full year with our air-to-water heat pump and are very pleased with the low costs for hot water, heating, and ventilation (combined unit).
When we compared the options back then, we included our assumptions about price developments. At the time, we expected gas (and fossil fuels in general) to rise significantly in price and for CO2 emissions to be taxed even more heavily. We also assumed that, in the long run, we would continue to have access to affordable electricity or possibly equip our building further with photovoltaic panels and battery storage.
Of course, these are only assumptions; none of us have a crystal ball. However, we both considered it unlikely that the price ratio between electricity and gas would remain the same over the long term. We strongly believe that gas will become more expensive.
When we compared the options back then, we included our assumptions about price developments. At the time, we expected gas (and fossil fuels in general) to rise significantly in price and for CO2 emissions to be taxed even more heavily. We also assumed that, in the long run, we would continue to have access to affordable electricity or possibly equip our building further with photovoltaic panels and battery storage.
Of course, these are only assumptions; none of us have a crystal ball. However, we both considered it unlikely that the price ratio between electricity and gas would remain the same over the long term. We strongly believe that gas will become more expensive.
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