Consultation for photovoltaic system

What do you save your 10 tons of CO2 per year with?

The phrase "save CO2" is odd. What exactly do you "save" there? Using less is already enough. I can sugarcoat it as a forest owner – however, the forest would also store CO2 as long as it is left standing, even if it is not in my possession. I can tell myself that refraining from intensive management is a contribution. I sometimes do that too. ;) I am still looking for about 10 hectares of contiguous deciduous forest in the Bergisches Land to leave standing and remove from management. Maybe someone has a tip for me.

The phrase "saving CO2" is strange.

Every generated kWh ensures that it does not have to be produced from fossil fuels. The average kWh in Germany has a CO2 footprint of 440g. This will ease with the increasing expansion of renewables - but currently I reduce Germany's CO2 footprint by about 2 gas heaters. And anyone with a roof can do that! And you even get paid for it!! How crazy is that?!?! :-)

Photovoltaic systems pay off after 11 to 12 years.

That is a bit too general for me. Under certain circumstances, certainly. With a turnkey, normal-sized system that is planned now and then only gets a feed-in tariff of max. 7,xx cents, probably not.

If I had written, "a photovoltaic system pays off in 8-18 years," would that have been better? ;-)

So: of course, as with all purchases, you need to do a bit of research beforehand to avoid the usual pitfalls. I’ll address your terms directly:

Turnkey: That’s what I meant. If you build it yourself, the system pays off in 2/3 of the time.

Normally sized: Normally sized is a system when all roof surfaces (house, garage, carport) are fully utilized, unless it faces FULL north AND is steeper than 25°. Normally sized is not what the solar installer recommends. He’s lazy and prefers to spend less time on the roof, so he can serve more customers with storage batteries... And yes – if you can only fit 5 kWp on a mid-terrace house, then the payback shifts backward, up to "unprofitability." These roofs will just have to wait until the next roof renovation...

Feed-in tariff: Once you have received your offer, you can calculate whether it is good. Determine the yield (yourself), multiply it by the feed-in tariff, times 20. If the offer is below that, good. If not, bad. The rest depends on self-consumption.

If you do it this way, 11-12 years is a good average. After that, you make money for 8 years and then have 18 years of cheap self-generated electricity.

You can optimize further by removing solar thermal systems and chimneys. Heat pumps will have to be installed in a few years anyway; currently, they are heavily subsidized. Moreover, heat pumps increase self-consumption and push the payback period further forward.

Two more notes:
- A storage battery does not pay off. Therefore, exclude it from calculations (and preferably also from the order).
- "No roof" is an excuse, "no money" is not. The KFW offers loans at 1%. Most banks are even cheaper since the installments are legally guaranteed to be paid by the energy supplier. So it is a very low-risk loan that everyone should get after talking to their banker.

We are getting a 13.29 kWp photovoltaic system. Now the question is whether a storage system is worth it without subsidies. I searched for storage systems on the internet myself and came across this one. The price already looks great. The question always is: a) Does the photovoltaic installer also install it? b) How good is it actually? Luckily, it will still take about 10 months until completion with us. I hope that by then the new storage subsidy will come in Brandenburg.

If you come under €250 per kWh, have three times more photovoltaics than storage, and you can more or less always empty the storage at night, it should pay off.

A small addition to my sermon above: Please also be very, very critical of cloud tariffs and google them beforehand. Most tariffs are already bad from the start. The main problem, however, is that people base their 20-year calculation on them. Currently, one of the biggest providers is canceling all its "good" contracts and thereby destroying the calculations of thousands of customers who were previously talked into an outrageously expensive huge storage as a cloud condition...