ᐅ Solar thermal systems or photovoltaic panels combined with a gas heating system

Hello everyone,

The construction of our single-family house has started, and so far it is planned to combine the gas heating system with solar thermal panels (about 5 sqm (54 sq ft) collectors, only for domestic hot water without heating support). Solar thermal seems to be mandatory as the renewable energy component and not my voluntary choice, even though a centralized controlled ventilation system with heat recovery is also being installed.

I have now asked the construction company if I could have photovoltaic panels instead of solar thermal. The answer was yes, but then the hot water tank (300 liters (79 gallons)) must be heated with a heating element using electricity from the photovoltaic system, controlled by a priority management system.

Now I am wondering what I would actually gain by making this swap. For the solar thermal system including the hot water tank, I would receive a subsidy of about 3700 euros. Then, there would be the cost of a 5 kWp photovoltaic system (I estimate somewhere between 7000 and 9000 euros) and the cost for an alternative hot water tank.

Since solar thermal is not cost-effective, I actually wanted to avoid it. I need your help to make an informed decision. Therefore, I have the following questions:

1. Is it technically possible to simply remove the priority management system after moving in?
2. Would that be legal, a gray area, or already illegal?
3. If the priority system has to remain in place (see question 2), does switching from solar thermal to photovoltaic make economic sense at all?

neutronbx schrieb:

3. If the priority must remain (see question 2), does swapping solar thermal for photovoltaic even make economic sense?

Photovoltaics always make sense. And be glad if your hot water tank is heated with cheap (your own) electricity instead of buying expensive power.
If you go for photovoltaics, make it as large as possible. 10 kWp should cost around €11,000–12,000. That way, you get a decent amount credited to your account every month.

neutronbx schrieb:

1. Can the priority be easily removed later after moving in?
2. Would that be legal, a gray area, or already illegal?

Anything that can be switched on can also be switched off...

nordanney schrieb:

Photovoltaics always make sense. And be glad if your hot water tank is heated using cheap (your own) electricity instead of buying it at a high price.
If you go for photovoltaics, make the system as large as possible. 10 kWp should cost around €11,000–12,000 (about $11,000–12,000). This will credit your account with a decent amount every month.

Anything you can switch on, you can also switch off again...

I think that achieving 10 kWp on our hipped roof with house dimensions of 11.30 x 8.30 m (37.1 x 27.2 ft) will be quite difficult. Or am I mistaken? A further challenge for good yield is that on the east side, the neighboring house is only 6 m (20 ft) away and is three stories high, so it will probably cast shade on the east side of the roof (see drawing). Or are my concerns unfounded?

You need to have it calculated.

Download the Photovoltaic SOL 30-day trial version and virtually rebuild your house, including the neighbor’s house.