Hello,
I want to have a house built— a single-family home with 112m² (1,206 sq ft) of living space. I assume that, according to the 2009 Energy Saving Ordinance, all houses are very well insulated. Since I’m not a fan of throwing my money away to big energy companies, the house will be equipped with an air-to-water heat pump, a ventilation system with heat recovery, and a photovoltaic system on the roof.
My simple thinking is this: the photovoltaic system generates electricity, the air-to-water heat pump uses electricity, and the ventilation system helps prevent mold and, because it operates with heat recovery, I won’t need as much electricity to keep the house warm.
I’m open to being convinced otherwise!
Best regards
I want to have a house built— a single-family home with 112m² (1,206 sq ft) of living space. I assume that, according to the 2009 Energy Saving Ordinance, all houses are very well insulated. Since I’m not a fan of throwing my money away to big energy companies, the house will be equipped with an air-to-water heat pump, a ventilation system with heat recovery, and a photovoltaic system on the roof.
My simple thinking is this: the photovoltaic system generates electricity, the air-to-water heat pump uses electricity, and the ventilation system helps prevent mold and, because it operates with heat recovery, I won’t need as much electricity to keep the house warm.
I’m open to being convinced otherwise!
Best regards
P
perlenmann23 Nov 2011 08:14@Micha: Where is the money for your photovoltaic system coming from? Is it from your savings? Then your calculation might work. If you have to finance it, it’s a waste!
Oh, by the way, a Scottish bank offers 2.7% on the checking account and 4.5% on fixed deposits. You had asked about that!
Oh, by the way, a Scottish bank offers 2.7% on the checking account and 4.5% on fixed deposits. You had asked about that!
M
Micha&Dany23 Nov 2011 13:13perlenmann schrieb:
@Micha: Where does the money for your photovoltaic system come from? Is it from savings? Then your calculation might work. If you have to finance it, it’s useless!
Oh, and a Scottish bank pays 2.7% on the checking account and 4.5% on fixed deposits. You asked about that!Hello Perlenmann
Okay, then a little detour into mathematics :p
Here: https://www.hausbau-forum.de/solar-energiefragen/4781-Viebrockhaus-haus-photovoltaikanlage.html#post28568
I calculated that in the Ruhr area you can expect a return of 4885 euros per kWp for a photovoltaic system.
>> Disclaimer: This is just an example. But a realistic one. You must always evaluate each system individually!
Let’s assume the 4885 euros.
Provisions are usually 1%.
Availability should be >97%.
The whole thing is financed through a standard loan – I’m leaving aside KfW loans for now.
A quick online search shows that currently you can get money at about 3.75% interest (variations up and down possible).
A system in 2011 must not cost more than 2100 euros per kWp.
I take that amount as a loan at 3.75% interest.
I receive 4885 euros from the government over 20 years – that means 244 euros per year.
Using an online loan calculator, repaying 2100 euros at 3.75% interest with an annual payment of 244 euros takes 10.59 years (including interest). The total cost is 2584 euros.
As mentioned, provisions should be 1% of the investment – 210 euros.
Availability 97%: 4885 * 97% = 4738 euros.
So: income: 4738 euros / expenses 2794 euros → 1944 euros profit.
If I calculated correctly, this corresponds to a return of 3.33% per year.
Okay, if interest rates on deposits rise again, you should reconsider. But at least the return is still higher than on a checking account now. And does your Scottish bank guarantee these rates for the full 20 years? I doubt it...
Doing the same calculation for Munich (about 980 kWh/kWp) results in a return of 4.25% – anyone can check the math themselves 😀
@Euro: Okay, then we misunderstood each other. I thought you meant general problems with photovoltaic systems.
Problems with heat pumps and photovoltaic systems only arise if the system is poorly planned, poorly built, incorrectly sized, or whatever. I am assuming proper planning and installation and the use of good materials.
Best regards
Micha 😎
Hello
(Heat pump, especially air source heat pump,) + photovoltaic is basically a very sensible combination.
Regards
Micha&Dany schrieb:That happens in the heat of the moment. 😉
...@Euro: Okay, then we misunderstood each other.
(Heat pump, especially air source heat pump,) + photovoltaic is basically a very sensible combination.
Regards
Micha&Dany schrieb:
Hello Perlenmann
Okay, here’s a brief detour into some math :p
Here: https://www.hausbau-forum.de/solar-energiefragen/4781-Viebrockhaus-haus-photovoltaikanlage.html#post28568
I calculated that in the Ruhr area you can expect a yield of 4885 euros per kWp for a photovoltaic system.
>> Disclaimer: This is just an example. But a realistic one. You always have to evaluate each system individually!
Let’s assume the 4885 euros.
Provisions are normally 1%.
Availability should be >97%.
This is financed through a regular loan – I am leaving out KfW loans for now.
A quick online search shows that you can currently get financing at 3.75% interest (rates may vary up or down).
A system in 2011 should not cost more than 2100 euros per kWp.
I am taking out a loan for this amount at 3.75% interest.
I receive 4885 euros total from the government over 20 years – that’s 244 euros per year.
An online loan calculator shows that with an annual payment of 244 euros, I can repay a 2100 euro loan at 3.75% interest in 10.59 years (including interest). The total cost ends up at 2584 euros.
Provisions, as mentioned, should be 1% of the investment – 210 euros.
Availability 97%: 4885 * 97% = 4738 euros.
So: Income: 4738 euros / Expenses 2794 euros -> 1944 euros profit
If I calculated correctly, that corresponds to a return of 3.33% per year.
Okay, if interest rates on savings accounts rise again, you might want to reconsider this. But at least this return is still higher than what you get on a regular savings account nowadays. And does your Scottish bank really guarantee the interest for the full 20 years? I doubt that...
If you do the same calculation for Munich (approx. 980 kWh/kWp), you get a return of 4.25% – feel free to check the numbers yourself 😀
@Euro: Okay, then we misunderstood each other. I thought you were talking about general issues with photovoltaics.
Problems with heat pumps and photovoltaics only occur when the system is poorly planned, badly constructed, incorrectly sized, or whatever else. I am assuming a properly planned and installed system using good materials.
Best regards
Micha 😎Very well explained, thanks. If I ever have a similar question, I know who to ask lol
P
perlenmann24 Nov 2011 08:22Micha&Dany schrieb:
If I’ve calculated correctly, that corresponds to a return of 3.33% per year.That means anyone who has extra money and doesn’t need a loan for it would actually get an even higher return.
Strange, why is this not done more often?
And who guarantees that the government will pay for 20 years?
It’s all too much for me. I don’t want to take on a bigger loan on top of the house just to maybe make some profit in 20 years.
If the numbers are correct, that would be nice… but still too risky for me.
P
perlenmann24 Nov 2011 10:29I’ve done some more reading to educate myself.
But you’re forgetting the additional costs for a meter (or are those already included in your €2100)?
You’ve overlooked the loss in yield over the system’s lifetime.
Are the maintenance costs supposed to be covered by the reserve funds? The inverters only have a lifespan of 5 to 10 years.
Besides, my mortgage payments decrease if I take out additional credit.
No one can say for sure if the system will last 20 years.
I might have made some mistakes as well, but I think you really need to calculate carefully here. For me (especially now), that’s too much risk.
But you’re forgetting the additional costs for a meter (or are those already included in your €2100)?
You’ve overlooked the loss in yield over the system’s lifetime.
Are the maintenance costs supposed to be covered by the reserve funds? The inverters only have a lifespan of 5 to 10 years.
Besides, my mortgage payments decrease if I take out additional credit.
No one can say for sure if the system will last 20 years.
I might have made some mistakes as well, but I think you really need to calculate carefully here. For me (especially now), that’s too much risk.
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