ᐅ Gas with solar thermal? Or heat pump with photovoltaic? Advice needed
Created on: 5 Feb 2020 08:57
M
Micha8589
Good morning to the forum,
I have been researching heating options for quite some time and have gathered a few opinions, which have only made me more uncertain about my decision. That’s why I thought I’d ask the forum.
My family (2 adults, 1 child) is planning to build the following single-family house at the end of this year or beginning of next year:
Single-family home with pitched roof
Approximately 115 m² (1,237 sq ft)
Solid construction (calcium silicate brick ground and upper floors, brick-clad)
No KFW standard
Building location: southern Mecklenburg
Unfortunately, I can’t provide an energy performance certificate or heating load calculation yet, as the preliminary offer is still being prepared. I am also aware that a general statement can’t really be made since every house and heating behavior is individual.
The construction company advised us to install a modern hybrid heating system consisting of a gas condensing boiler and two solar thermal panels on the roof for domestic hot water, as the initial costs are relatively low (plus installation of the central gas connection), and this technology has proven reliable. The entire house is planned to have underfloor heating. According to the company, they have had very positive experiences with this and consider the technology future-proof. (There is also the idea of a fireplace in the living room.)
On the other hand, I think gas prices will not get any cheaper in the future, and the topic of CO₂ taxes (especially concerning the fireplace) worries me somewhat.
In theory, I would prefer to install a geothermal heat pump combined with a suitable photovoltaic system because this would make me independent of fossil fuels and allow me to heat “off-grid” to a certain extent, depending on efficiency. However, I am hesitant because of the very high initial costs and don’t really know how these compare to operational costs. I also can no longer realistically assess which technology offers the best cost-performance ratio (except for air-source heat pumps).
As you can see, I am completely undecided and hope to get some feedback and expertise from the forum.
Thanks in advance for your replies.
I have been researching heating options for quite some time and have gathered a few opinions, which have only made me more uncertain about my decision. That’s why I thought I’d ask the forum.
My family (2 adults, 1 child) is planning to build the following single-family house at the end of this year or beginning of next year:
Single-family home with pitched roof
Approximately 115 m² (1,237 sq ft)
Solid construction (calcium silicate brick ground and upper floors, brick-clad)
No KFW standard
Building location: southern Mecklenburg
Unfortunately, I can’t provide an energy performance certificate or heating load calculation yet, as the preliminary offer is still being prepared. I am also aware that a general statement can’t really be made since every house and heating behavior is individual.
The construction company advised us to install a modern hybrid heating system consisting of a gas condensing boiler and two solar thermal panels on the roof for domestic hot water, as the initial costs are relatively low (plus installation of the central gas connection), and this technology has proven reliable. The entire house is planned to have underfloor heating. According to the company, they have had very positive experiences with this and consider the technology future-proof. (There is also the idea of a fireplace in the living room.)
On the other hand, I think gas prices will not get any cheaper in the future, and the topic of CO₂ taxes (especially concerning the fireplace) worries me somewhat.
In theory, I would prefer to install a geothermal heat pump combined with a suitable photovoltaic system because this would make me independent of fossil fuels and allow me to heat “off-grid” to a certain extent, depending on efficiency. However, I am hesitant because of the very high initial costs and don’t really know how these compare to operational costs. I also can no longer realistically assess which technology offers the best cost-performance ratio (except for air-source heat pumps).
As you can see, I am completely undecided and hope to get some feedback and expertise from the forum.
Thanks in advance for your replies.
Thank you for this thread; I am currently dealing with the same question.
I bought an old building from 1956, and the upper floor is now undergoing a complete renovation with a new roof rated at U=0.14, new windows, and underfloor heating.
The ground floor remains as it is for now because my grandfather still lives there, along with the radiators.
Currently, there is an electric night storage heater that consumes about €3600-3800 in electricity per year, for two occupied floors totaling around 78m² (excluding interior walls). The basement is uninsulated.
The facade was insulated years ago with 6cm (2.4 inches) of polystyrene.
When my grandfather can no longer live there, the ground floor will also be fully renovated with underfloor heating and new windows; a single-story extension will add 32m² (344 square feet) of living space to the ground floor.
So this results in three different heating scenarios: existing condition → renovation stage 1 (upper floor only) → renovation stage 2 (including ground floor with extension). The heating system to be installed now should of course be capable of handling both renovation stages.
I was initially quite confident that an air-to-water heat pump combined with photovoltaics and an energy storage system would be the solution. My architect and energy consultant are also fans of this approach.
However, I have since developed doubts—both about my energy consultant and about the solution itself. I have not yet seen a calculation of my actual heating demand; everything seems somewhat based on gut feeling and experience. At least the energy efficiency funding application for the individual measure “roof” was approved, so the consultant can’t be entirely wrong.
The upfront costs are substantial. For a 9.9kWp photovoltaic system with a 10kWh battery, I’m looking at a fully installed cost of €23,000.
The air-to-water heat pump Wolf CHC10/400 + 280-liter (74 gallon) hot water tank + 50-liter (13 gallon) hydraulic separator with piping and installation costs about €25,000 (the only quote I have so far; it seems somewhat expensive to me). I also feel the hydraulic separator is undersized.
I have read a lot, including this whole thread and various other sources, and of course there are many pros and cons. What really makes me doubt the heat pump solution is a study that monitored heat pump systems in practice over two years using evaluated measurement technology. I’m not allowed to post links here, but if you google “Wärmepumpen-praxistest,” you will find the study, in which Fraunhofer IBP was involved.
With these figures, it is difficult for me to justify such a large investment, especially since it may be several years before my grandfather no longer lives there. I now think that I might be better off with a gas condensing boiler combined with solar thermal, mainly because that combination would also cover renovation stage 1, offer more flexibility, and allow me to keep larger performance reserves at a much lower cost. I don’t yet have a quote for gas + solar thermal, but I expect the total cost to be no more than €12,000.
That’s where I am in my thought process so far. I would appreciate any comments and suggestions.
I bought an old building from 1956, and the upper floor is now undergoing a complete renovation with a new roof rated at U=0.14, new windows, and underfloor heating.
The ground floor remains as it is for now because my grandfather still lives there, along with the radiators.
Currently, there is an electric night storage heater that consumes about €3600-3800 in electricity per year, for two occupied floors totaling around 78m² (excluding interior walls). The basement is uninsulated.
The facade was insulated years ago with 6cm (2.4 inches) of polystyrene.
When my grandfather can no longer live there, the ground floor will also be fully renovated with underfloor heating and new windows; a single-story extension will add 32m² (344 square feet) of living space to the ground floor.
So this results in three different heating scenarios: existing condition → renovation stage 1 (upper floor only) → renovation stage 2 (including ground floor with extension). The heating system to be installed now should of course be capable of handling both renovation stages.
I was initially quite confident that an air-to-water heat pump combined with photovoltaics and an energy storage system would be the solution. My architect and energy consultant are also fans of this approach.
However, I have since developed doubts—both about my energy consultant and about the solution itself. I have not yet seen a calculation of my actual heating demand; everything seems somewhat based on gut feeling and experience. At least the energy efficiency funding application for the individual measure “roof” was approved, so the consultant can’t be entirely wrong.
The upfront costs are substantial. For a 9.9kWp photovoltaic system with a 10kWh battery, I’m looking at a fully installed cost of €23,000.
The air-to-water heat pump Wolf CHC10/400 + 280-liter (74 gallon) hot water tank + 50-liter (13 gallon) hydraulic separator with piping and installation costs about €25,000 (the only quote I have so far; it seems somewhat expensive to me). I also feel the hydraulic separator is undersized.
I have read a lot, including this whole thread and various other sources, and of course there are many pros and cons. What really makes me doubt the heat pump solution is a study that monitored heat pump systems in practice over two years using evaluated measurement technology. I’m not allowed to post links here, but if you google “Wärmepumpen-praxistest,” you will find the study, in which Fraunhofer IBP was involved.
With these figures, it is difficult for me to justify such a large investment, especially since it may be several years before my grandfather no longer lives there. I now think that I might be better off with a gas condensing boiler combined with solar thermal, mainly because that combination would also cover renovation stage 1, offer more flexibility, and allow me to keep larger performance reserves at a much lower cost. I don’t yet have a quote for gas + solar thermal, but I expect the total cost to be no more than €12,000.
That’s where I am in my thought process so far. I would appreciate any comments and suggestions.
Such studies should always be approached with caution...
Basically, this is a case of overthinking and unnecessary panic.
Photovoltaic systems should not be included in the calculation since they pay for themselves or even generate profit. A storage system is pointless.
Whether it’s an air-to-water heat pump or gas, you can run the numbers in every possible way—positive, negative, or neutral—but it doesn’t really help.
Both work; both require a sensible overall plan. For radiator heating and partial renovations, it’s better to choose a gas boiler (if gas is available).
However, the €12,000 is also a rough estimate since you still need the connection and a chimney. It shouldn’t be cheaper than an air-to-water heat pump.
Basically, this is a case of overthinking and unnecessary panic.
Photovoltaic systems should not be included in the calculation since they pay for themselves or even generate profit. A storage system is pointless.
Whether it’s an air-to-water heat pump or gas, you can run the numbers in every possible way—positive, negative, or neutral—but it doesn’t really help.
Both work; both require a sensible overall plan. For radiator heating and partial renovations, it’s better to choose a gas boiler (if gas is available).
However, the €12,000 is also a rough estimate since you still need the connection and a chimney. It shouldn’t be cheaper than an air-to-water heat pump.
Lumpi_LE schrieb:
Such studies should always be taken with caution... Of course, but probably no more cautious than efficiency simulations of air-to-water heat pumps aiming to push an annual performance factor above 3.3 just to qualify for BAFA funding. I find the study quite solid, and if it shows an average annual performance factor of only 2.6 for air-to-water heat pumps in climate zone 2, and just 2.2 on average for the entire heating circuit including domestic hot water, then I do wonder why my system should perform better than the average. Even if I end up at the average, a realistic annual performance factor of 2.2 means significantly higher running costs than what I was calculated.
Lumpi_LE schrieb:
Basically, this is a case of overthinking and unnecessary worry. You’re probably right there. I’m considering consulting another energy advisor, though that might be wasted money since the energy consulting subsidy is only available once.
Lumpi_LE schrieb:
For radiators and partial renovations, it’s better to choose a gas heating system. Yep, I also think that’s the crucial point. Thank you very much for your opinion.
A chimney is already installed, and we want to continue using an existing tiled stove simply because it’s so charming.
Gas is available in the street; connection costs are €2400, and the quote is already available.
Diedler schrieb:
And even if I were to be average, with a realistic annual performance factor of 2.2, I would have significantly higher operating costs than calculated for me.My air-to-water heat pump has an annual performance factor of 4.3—I can’t imagine that an air-to-water heat pump can be built so poorly that it only achieves an annual performance factor of 2.2...Similar topics