ᐅ Solar panels for domestic hot water

Created on: 2 Jul 2015 12:49
C
chrischn
Hello,
we are planning to build a detached house with about 200 sqm (2,150 sq ft) of living space.
The heating system will be a gas condensing boiler.
In the living and dining area, there will be a water-bearing stove.
And photovoltaic panels on the roof.

Our energy consultant said that if we want KfW 70 (a German energy efficiency standard), we need to install solar thermal panels on the roof instead of photovoltaic panels. But I would actually prefer not to do that.

Now to my question: Does solar thermal for hot water provide the same benefits as photovoltaic?
On the one hand for the KfW application,
and on the other hand from an energy perspective? And economically?

Thanks for your experience and input.
Best regards
C
chrischn
3 Jul 2015 11:35
Ok, we have actually gotten off topic 🙂

Does anyone have experience with a so-called photovoltaic heater?
L
Legurit
3 Jul 2015 17:38
Photovoltaic heaters are essentially just tankless water heaters that you end up powering with regular electricity in winter anyway, or am I mistaken?
I would advise against it.
C
chrischn
3 Jul 2015 18:05
I just thought that they heat the boiler like an electric kettle 🙂
L
Legurit
3 Jul 2015 18:10
That actually makes more sense 😀
But then you need a large tank and will always have heat loss – it’s unclear if that’s cost-effective. A 1000 L (260 gallon) tank probably costs around 1000 €. So why not just use a heat pump? Definitely more economical and cheaper – I don’t see any advantage in using electricity as the medium.
O
oleda222
3 Jul 2015 18:41
Layman's opinion:

If you install a standard photovoltaic system combined with a heat pump, you can even power appliances like the kettle, stove, washing machine, etc., instead of using a "photovoltaic heater," which involves heating an oversized hot water tank cheaply with solar power in summer and expensively with external electricity in winter.

Better to choose a small hot water storage tank and use the photovoltaic electricity for something more "useful," even if that just means selling the surplus back to the utility company.

If a battery becomes worthwhile, you can add it later.
C
chrischn
3 Jul 2015 20:27
Okay, that’s one opinion. Thanks. But maybe someone else has a different view or can confirm this for me 🙂

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