ᐅ Comparison of Geothermal Heat Pump and Air-to-Water Heat Pump
Created on: 8 Aug 2020 22:33
M
mjammjammjam
Starting point: In the builder’s cost estimate, an air-to-water heat pump Nibe F2040 with a 180-liter (48-gallon) hot water tank is listed. Additionally, there are electric towel radiators and appropriate insulation to meet KfW-40 house standards. This package is supposed to cost us €13,900.
After some research, I found out that ground source heat pumps have a higher annual performance factor. According to the builder’s catalog, the air-to-water heat pump has a COP of 3.6, while the ground source heat pump has at least 4.5. In this case, it is a Nibe 1255.
Even though I don’t yet know the potential price for the 1255 from the builder, I would like to ask,
I look forward to your answers, as a non-expert I feel a bit lost here (at least I do right now)...
After some research, I found out that ground source heat pumps have a higher annual performance factor. According to the builder’s catalog, the air-to-water heat pump has a COP of 3.6, while the ground source heat pump has at least 4.5. In this case, it is a Nibe 1255.
Even though I don’t yet know the potential price for the 1255 from the builder, I would like to ask,
- what you paid for any borehole drilling for the ground loops?
- how the running costs compare between air-to-water and ground source heat pumps
- what you had to pay for your eligible Nibe units
I look forward to your answers, as a non-expert I feel a bit lost here (at least I do right now)...
We decided on an air-to-water heat pump combined unit with controlled mechanical ventilation. Tecalor THZ 504. We will be able to share our experience only in a few months.
In terms of cost, it was comparable to a gas boiler with our general contractor, thanks to the BAFA subsidy. We would have installed controlled mechanical ventilation regardless. The gas boiler was practically included in the house price, while the Tecalor came with an additional cost of about 17,000€ (about 18,200 USD). In return, we receive 10,000€ (about 10,700 USD) from BAFA, 2,000€ (about 2,140 USD) savings from not needing a gas connection, and roughly 5,000€ (about 5,350 USD) saved from not requiring a separate controlled ventilation system — so, for us, it’s basically a break-even scenario.
We also expect synergies between the unit and our photovoltaic system, aiming to increase self-consumption.
How the operating and maintenance costs will turn out remains to be seen. For the gas boiler in our old house, we had annual maintenance costs of around 90€ (about 95 USD), and that was it.
In terms of cost, it was comparable to a gas boiler with our general contractor, thanks to the BAFA subsidy. We would have installed controlled mechanical ventilation regardless. The gas boiler was practically included in the house price, while the Tecalor came with an additional cost of about 17,000€ (about 18,200 USD). In return, we receive 10,000€ (about 10,700 USD) from BAFA, 2,000€ (about 2,140 USD) savings from not needing a gas connection, and roughly 5,000€ (about 5,350 USD) saved from not requiring a separate controlled ventilation system — so, for us, it’s basically a break-even scenario.
We also expect synergies between the unit and our photovoltaic system, aiming to increase self-consumption.
How the operating and maintenance costs will turn out remains to be seen. For the gas boiler in our old house, we had annual maintenance costs of around 90€ (about 95 USD), and that was it.
kati1337 schrieb:
We decided on an air-to-water heat pump combination unit with controlled mechanical ventilation. Tecalor THZ 504. We can only share our experience after a few months.
In terms of price, it was about the same as a gas boiler with our general contractor, thanks to the BAFA subsidy.
Either way, we would have installed controlled mechanical ventilation. The gas boiler was basically included in the house price, Tecalor came with an additional cost of around 17,000€ (about 18,700 USD). In return, we receive 10,000€ (about 11,000 USD) from BAFA, 2,000€ (about 2,200 USD) saved from not having a gas connection, and approximately 5,000€ (about 5,500 USD) saved by not having a separate controlled mechanical ventilation system—so, for us, it’s almost a break-even. We also hope to create synergies between this system and our photovoltaic installation to increase our self-consumption.
How operating and maintenance costs will turn out remains to be seen. With the gas boiler in our old house, we had about 90€ (about 100 USD) annual maintenance costs, and that was it. I consider that unwise. If one of the two components fails, it will probably become quite expensive.
Joedreck schrieb:
I think that’s unwise. If one of the two components fails, it will probably become very expensive. I’m not a fan of combined units either. What happens if the air-to-water heat pump breaks down after 20 years, but the mechanical ventilation with heat recovery still works? You either have to replace both or end up with a large cabinet that only serves as the ventilation system (if that’s even possible).
FoxMulder24 schrieb:
There are a few air-to-water heat pumps that achieve a seasonal performance factor (SPF) of 4.5.
For example, we will install the CHA-07 from Wolf. With this, we expect to reach an SPF of 4.6.At first, I was about to say that I don’t quite believe that, but then I noticed the word "will" in the quote. So this is not based on practical experience.According to the datasheet, the mentioned pump has the following COP values:
A2/W35 4.54
A7/W35 5.47
A10/W35 5.88
A-7/W35 2.73
I have illustrated this graphically here:
Now think about when your heating system needs to deliver the highest output: at 10°C (50°F) outdoor temperature or below 0°C (32°F) outdoor temperature?
In the overall calculation of the seasonal performance factor, the auxiliary power consumption (circulation pumps, fans, electronics, etc.) is also included. Therefore, the SPF deviates more from the COP during mild transitional months and could theoretically even drop below 1.
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T_im_Norden13 Aug 2020 10:12And?
With all heat pumps, the efficiency decreases as the temperature drops.
What matters for the subsidy is the value calculated by the annual performance factor calculator.
With all heat pumps, the efficiency decreases as the temperature drops.
What matters for the subsidy is the value calculated by the annual performance factor calculator.
COP and calculated annual performance factor are theoretical values. The fact is, they are always improving, at least in the lab. Practical results are still pending as the models are too new.
Maybe it’s also time for the BAFA to adjust its criteria.
Exactly. However, you can use heat sources that are less affected by seasonal fluctuations. They tend to be the least efficient precisely when they are most needed. But this depends on the region and the winter conditions.
In the last heating season, January 2020 was the month with the highest heat energy consumption in our house: 1641 kWh of heat including hot water. With a performance factor (including pumps and controls) of 4.69 and 350 kWh of electricity.
If I consider that a common air-to-water heat pump might have achieved about 3.5, that would have meant over $30 more in electricity costs just for heating the house in that month. And we had five such months this season...
Last calendar year, I used 2200 kWh of electricity to keep a four-person household, including hot water, warm in a 200 sqm (2150 sq ft) home. That corresponds here to about €572 per year or €48 per month using household electricity (not a heat pump tariff). However, this is not entirely accurate since part of the consumption came from our own photovoltaics, so actual energy costs are slightly lower. Maintenance costs are zero.
I am therefore still very satisfied with a ground-source heat pump using drilling.
Maybe it’s also time for the BAFA to adjust its criteria.
T_im_Norden schrieb:
This is the case with all heat pumps: the efficiency decreases the colder it gets.
Exactly. However, you can use heat sources that are less affected by seasonal fluctuations. They tend to be the least efficient precisely when they are most needed. But this depends on the region and the winter conditions.
In the last heating season, January 2020 was the month with the highest heat energy consumption in our house: 1641 kWh of heat including hot water. With a performance factor (including pumps and controls) of 4.69 and 350 kWh of electricity.
If I consider that a common air-to-water heat pump might have achieved about 3.5, that would have meant over $30 more in electricity costs just for heating the house in that month. And we had five such months this season...
Last calendar year, I used 2200 kWh of electricity to keep a four-person household, including hot water, warm in a 200 sqm (2150 sq ft) home. That corresponds here to about €572 per year or €48 per month using household electricity (not a heat pump tariff). However, this is not entirely accurate since part of the consumption came from our own photovoltaics, so actual energy costs are slightly lower. Maintenance costs are zero.
I am therefore still very satisfied with a ground-source heat pump using drilling.
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