ᐅ Heat Pump with Photovoltaic System vs. Gas Heating and Solar Thermal Energy
Created on: 7 Jun 2016 21:53
I
inconel
Hello everyone,
for my house construction, which will start next year, I would like to gather information about the heating system, specifically regarding the two options:
+ Gas condensing boiler, supported by approximately 12m² (130 sq ft) of solar thermal panels and a wood stove
+ Groundwater heat pump powered by a photovoltaic system
About the property:
+ Planned is a 10x11m (33x36 ft) house with two full floors, a basement, a hip roof with about 35m² (375 sq ft) of south-facing roof area, and approximately 200m² (2,150 sq ft) of living space.
+ Exterior walls made of 36.5cm (14 inches) perlite-filled bricks “Poroton T7”
+ Location: Bavaria, with an average annual solar radiation of about 1000 kWh/m²
Option 1: Gas condensing boiler
Advantages:
- Proven, durable gas condensing technology (efficient)
- Fast response time of the gas heating system, requires no long preheating
- From around April to October, the thermal energy from the solar panels is sufficient (no gas needed); in winter, supported by the wood stove for both hot water and heating
Disadvantages:
- Solar panels need to be cooled relatively early in summer, meaning little hot water is required but excess heat must be dissipated from the panels → increased electricity and water costs without added benefit
- Large domestic hot water storage tank needed to utilize countercyclical heating periods
Option 2: Photovoltaics with heat pump
Advantages:
- Autonomous heat and electricity production
- “Green energy”
- Additional support for other continuous electricity consumers (refrigerator, freezer, washing machine, dryer)
- Relatively low effort to install suction and discharge wells, as groundwater is already available at about 2.5m (8 ft) depth
Disadvantages:
- High investment costs for both photovoltaic system and heat pump (long payback period)
- Limited sunshine during months with high energy demand
- Complex and expensive, but still necessary, storage solutions for photovoltaic electricity
I hope you can understand my concerns and ideas, and I would really appreciate your feedback. How do you see the situation? What do you think is truly practical?
Thank you very much
Best regards
for my house construction, which will start next year, I would like to gather information about the heating system, specifically regarding the two options:
+ Gas condensing boiler, supported by approximately 12m² (130 sq ft) of solar thermal panels and a wood stove
+ Groundwater heat pump powered by a photovoltaic system
About the property:
+ Planned is a 10x11m (33x36 ft) house with two full floors, a basement, a hip roof with about 35m² (375 sq ft) of south-facing roof area, and approximately 200m² (2,150 sq ft) of living space.
+ Exterior walls made of 36.5cm (14 inches) perlite-filled bricks “Poroton T7”
+ Location: Bavaria, with an average annual solar radiation of about 1000 kWh/m²
Option 1: Gas condensing boiler
Advantages:
- Proven, durable gas condensing technology (efficient)
- Fast response time of the gas heating system, requires no long preheating
- From around April to October, the thermal energy from the solar panels is sufficient (no gas needed); in winter, supported by the wood stove for both hot water and heating
Disadvantages:
- Solar panels need to be cooled relatively early in summer, meaning little hot water is required but excess heat must be dissipated from the panels → increased electricity and water costs without added benefit
- Large domestic hot water storage tank needed to utilize countercyclical heating periods
Option 2: Photovoltaics with heat pump
Advantages:
- Autonomous heat and electricity production
- “Green energy”
- Additional support for other continuous electricity consumers (refrigerator, freezer, washing machine, dryer)
- Relatively low effort to install suction and discharge wells, as groundwater is already available at about 2.5m (8 ft) depth
Disadvantages:
- High investment costs for both photovoltaic system and heat pump (long payback period)
- Limited sunshine during months with high energy demand
- Complex and expensive, but still necessary, storage solutions for photovoltaic electricity
I hope you can understand my concerns and ideas, and I would really appreciate your feedback. How do you see the situation? What do you think is truly practical?
Thank you very much
Best regards
even if it doesn’t quite match your previous statement that one should always use ST I wrote that I would always install ST again and again. Over the past years, I have retrofitted ST in some of my rental properties, even though for a landlord this is actually counterproductive because I cannot pass on the costs. One example: in a 12-family building, a system with 35sqm (375 sq ft) was installed. Investment after subsidies was €17,000. Reduction of heating oil consumption averaged 3,500 liters (920 gallons). Average consumption 1995-2008 was 17,000 liters (4,490 gallons), and 2008-2013 it was 13,500 liters (3,570 gallons). Additional heating electricity costs were about €200. This is not directly applicable to a single-family house with 4 people (there are on average 25 people living in this property), but it does show the benefits of ST. And the effort to install ST is manageable. The system provides usable amounts of hot water from March to September. I have a Raspberry Pi with temperature sensors on the buffer tank and flow/return lines for logging, to see exactly what runs when.
In a two-family house with 6 residents, the savings are about €150 per year (heating oil before 1,900 liters (500 gallons), after 1,600 liters (420 gallons)). In this case, I had already prepared the buffer tank and riser pipes during construction in 2001 and only added the collectors and a pump (investment around €2,000) in 2012.
That’s why I make this statement, and that’s also why I have ST in my current property.
And here the rule also applies: EVERYONE has to decide for themselves. What works for me does not have to work for others. Some people drive Porsche, I drive Skoda—not saying I have anything against Porsche...
I am a fan of masonry stoves and ST, and if a heat pump makes financial sense, I would also install a heat pump, but so far heat pumps have always been more expensive!!! In the 12-family property, there was also consideration to install a combined heat and power unit (CHP), but this would have required tenants to use the electricity, and that is difficult; otherwise, that would also have been an option.
You wrote that you would always do that, but you didn’t include your specific situation, which is why your statement is being criticized!
My annual hot water costs are about €75 per year, and even if solar thermal systems could cover 100 percent of hot water, it wouldn’t pay off because the costs for the solar thermal system and the buffer tank are too high.
My annual hot water costs are about €75 per year, and even if solar thermal systems could cover 100 percent of hot water, it wouldn’t pay off because the costs for the solar thermal system and the buffer tank are too high.
I have always said that THIS is how I do it, NEVER that everyone should do it this way.
And I have always wanted to understand HOW the calculations are done because it is often said that the annual costs are very low. When I asked where the ROI of the heat pump is, I was told that there is no ROI for the heating system, but this was never explained. Well, I just wanted to know WHERE the additional investment in the heat pump pays off (ROI of the ADDITIONAL COSTS).
You wrote that your annual energy demand was 8,400 kWh.
What I have calculated now is simply how much 8,400 kWh would cost in oil or gas. At the current oil price, that would be about €500 (approximately $540), compared to which you have €200 (about $215) for electricity. For me, that means you save €300 (around $320) per year.
A gas boiler with 8 kW output and a standard efficiency of 109% costs about €2,000 ($2,150), a buffer tank €1,500 ($1,610), and a 5 m² (54 ft²) solar thermal system €1,500 ($1,610) — a total of €5,000 ($5,370), (these prices are current from the internet).
A gas underground tank costs about €2,500 ($2,680), so together that’s €7,500 ($8,050).
Your investment was €20,200 ($21,650) for the heat pump and drilling. Additional costs of €12,700 ($13,600).
There are additional yearly costs for the gas condensing boiler such as chimney sweep and maintenance of about €200 ($215). So, the annual additional costs amount to about €500 ($540).
With this calculation, I come to the conclusion that it would take 25 years to recover the additional investment. Will your heat pump last that long?
My neighbor’s ground-source heat pump broke down after 11 years. He bought a new one for €7,500 ($8,050) which, according to him, runs better and more efficiently than the old one…
I have no problem if you say (like tabtab) that you simply account for the additional investment as a ‘luxury,’ just as I did with my stove. But to say the heat pump is CHEAPER, in my view (unless I have made a serious mistake in thinking), is simply not the case.
Maybe you can point out my thinking or calculation error.
Addendum: I have not included the yield of the solar thermal system (in my experience about 10–15%).
And I have always wanted to understand HOW the calculations are done because it is often said that the annual costs are very low. When I asked where the ROI of the heat pump is, I was told that there is no ROI for the heating system, but this was never explained. Well, I just wanted to know WHERE the additional investment in the heat pump pays off (ROI of the ADDITIONAL COSTS).
You wrote that your annual energy demand was 8,400 kWh.
What I have calculated now is simply how much 8,400 kWh would cost in oil or gas. At the current oil price, that would be about €500 (approximately $540), compared to which you have €200 (about $215) for electricity. For me, that means you save €300 (around $320) per year.
A gas boiler with 8 kW output and a standard efficiency of 109% costs about €2,000 ($2,150), a buffer tank €1,500 ($1,610), and a 5 m² (54 ft²) solar thermal system €1,500 ($1,610) — a total of €5,000 ($5,370), (these prices are current from the internet).
A gas underground tank costs about €2,500 ($2,680), so together that’s €7,500 ($8,050).
Your investment was €20,200 ($21,650) for the heat pump and drilling. Additional costs of €12,700 ($13,600).
There are additional yearly costs for the gas condensing boiler such as chimney sweep and maintenance of about €200 ($215). So, the annual additional costs amount to about €500 ($540).
With this calculation, I come to the conclusion that it would take 25 years to recover the additional investment. Will your heat pump last that long?
My neighbor’s ground-source heat pump broke down after 11 years. He bought a new one for €7,500 ($8,050) which, according to him, runs better and more efficiently than the old one…
I have no problem if you say (like tabtab) that you simply account for the additional investment as a ‘luxury,’ just as I did with my stove. But to say the heat pump is CHEAPER, in my view (unless I have made a serious mistake in thinking), is simply not the case.
Maybe you can point out my thinking or calculation error.
Addendum: I have not included the yield of the solar thermal system (in my experience about 10–15%).
So, my system cost 12,500 (and that includes everything and is definitely larger than what a typical single-family house requires), yet there is still a difference of €7,500 and a payback period of 15 years.
It’s true that a gas condensing boiler can break down, but a replacement costs at most 3,000 (including labor).
And your statement about solar thermal is also accurate: with 15% savings, I get a payback period of 20 years.
However, your response seems to confirm that my calculation (apart from the points you mentioned) is essentially correct.
Of course, I see this only as a snapshot as of today. Who knows how technology will develop in the next few years. For a passive house, everything looks very different again...
To sum up, I conclude that a heat pump with your cost/consumption figures pays off after 15 years. That’s exactly what I wanted—ROI = 15 years. If it breaks down before then, well, that’s just how it is...
And my decision is also confirmed. (The heat pump offer I had was much more expensive than your investment.) Because only after 15 years would my gas condensing boiler/solar thermal solution be more expensive than your heat pump. If in 15 years heat pumps have become significantly cheaper due to advancements and sales volume, or if something completely different comes to market, I can still switch without having wasted money!!!
It’s true that a gas condensing boiler can break down, but a replacement costs at most 3,000 (including labor).
And your statement about solar thermal is also accurate: with 15% savings, I get a payback period of 20 years.
However, your response seems to confirm that my calculation (apart from the points you mentioned) is essentially correct.
Of course, I see this only as a snapshot as of today. Who knows how technology will develop in the next few years. For a passive house, everything looks very different again...
To sum up, I conclude that a heat pump with your cost/consumption figures pays off after 15 years. That’s exactly what I wanted—ROI = 15 years. If it breaks down before then, well, that’s just how it is...
And my decision is also confirmed. (The heat pump offer I had was much more expensive than your investment.) Because only after 15 years would my gas condensing boiler/solar thermal solution be more expensive than your heat pump. If in 15 years heat pumps have become significantly cheaper due to advancements and sales volume, or if something completely different comes to market, I can still switch without having wasted money!!!
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