Ba-Wü photovoltaic requirement for old buildings - renewing roof tiles

Hello dear forum,

maybe some of you have had the same situation/question.
I can't find anything clear online here.

The following initial situation.

- House (solid construction) from 1970
- Heating system with storage heaters (100% eco tariff for electricity), plus a tiled stove
- Roof insulated with insulation between the rafters, attic insulated (XPS boards), plastic windows with double glazing,
so of course not a modern insulation standard
- Annual energy consumption - day electricity (HT) 2500 kWh - night electricity (NT) 7400 kWh
- most of the living rooms are heated with the tiled stove

In the next few years the roof tiles will have to be replaced. According to my knowledge, I would then have to install a photovoltaic system in Ba-Wü.
So the question for me is:

- how am I supposed to finance this with the current high interest rates? The monthly burden including the mortgage would simply be too high.
- we also cannot afford a complete renovation (insulation, new windows, heat pump, etc.)
- as far as I know, you cannot power storage heaters with a photovoltaic system, even with battery storage, because those things consume too much electricity.
Besides, in winter, when we need a lot of electricity, too little electricity is generated...
- thus, at most a small photovoltaic system that covers our daytime consumption (approx. 2500 kWh per year) would make sense.
- I have come to the conclusion that such a system is not worthwhile for us up to now, especially with the high purchase prices including high interest rates.
Can the photovoltaic obligation be avoided if you do not have the financial means and only need to renew your tiles?


Has anyone of you had the same initial situation and how did you proceed, or what have you planned?

Many thanks!

You can't avoid them, but you can look for a good offer. Then it reasonably pays off through the feed-in tariff. A larger system is generally more economical than minimal mandatory compliance.

- how am I supposed to finance this with the current high . The monthly burden including the mortgage would simply be too high.

That's why you think about which measures will be due in the next few years before buying and adjust your bid accordingly. No whining afterwards; if you bought recently, the photovoltaic obligation was known.

Do you have an electricity tariff where you can charge the storage heaters more cheaply at night? If not, and you pay normal electricity prices (or almost normal electricity prices) for charging the storage heaters, then it might also be an option to charge them at midday when the photovoltaic electricity is available. Yes, that won't be enough in winter, but especially in the transitional period, I can imagine that you could use the photovoltaic electricity very well and use a lot more of the electricity yourself than the average, thereby significantly reducing your electricity costs. Which is why photovoltaic systems can pay off much faster than is the case for many. Of course, it very much depends on how your setup and electricity tariffs currently are. But the idea that you can't feed them with photovoltaic power "because they draw too much electricity" sounds very strange to me at first. (That you might not be able to fully charge them is one thing, but it should still help?!)

Otherwise, regarding financial aspects. There are, as far as I know, a few credit options through Kfw and through the L-Bank for photovoltaic systems, but it is true that these are currently not particularly low-interest. Depending on how much time you still have (you said "in the next few years"), I would start saving for it now so that you might not need that much credit. And some things might even become a bit cheaper if you can combine it with the roof tile replacement. So possibly there is scaffold anyway, and possibly you can directly plan for carrier tiles (tiles that directly integrate the carrier for the photovoltaic system) instead of having to remove and cut existing tiles. (I'm not sure if that really comes cheaper or not). Alternatively, you can probably save a lot on photovoltaic if you trust yourself to do the installation and then only pay someone for the connection (but that would not be for me either) – but often this is not allowed with the subsidized loans either, so installation by a professional company is often mandatory.

Hello everyone,

thanks for the first responses.
When we bought the house, there was no talk about a photovoltaic obligation yet.
And anyone who has bought a house in the Stuttgart metropolitan area in recent years knows what price level we are talking about here.
There are still financial reserves, but I am not investing in a project that presumably will never really pay off/ amortize.

That is correct, we currently have an off-peak electricity heating tariff NT (about 19 cents) and peak time HT (28 cents) with 100% green electricity.
So, in theory, we are heating 100% renewably.

I have to get some offers made by the local solar providers including financing options (L-Bank, KFW etc.)
and make a cost/benefit calculation. At least the daytime demand and the three hot water boilers could be supplied by the photovoltaic system.
Yes, I have an acquaintance who is a roofer, maybe it could also be done privately...

Does anyone actually have experience with infrared or electric underfloor heating, are they more effective than night storage heaters?

Best regards

Does anyone have the same starting situation and how did you proceed here, or what have you planned?

No personal experience. But there are also exceptional rules in Baden-Württemberg. Unreasonable hardship is included - a missing loan commitment can be a reason. Your bank will certainly assist you in case of loan rejection. If you yourself already say that you cannot afford it, the bank will surely say nothing different.

There are still financial reserves, but I don’t invest in a project that probably will never really pay off / amortize.

That is a misconception. There is basically no situation where a photovoltaic system does not pay off. With the highest possible self-consumption, amortization periods of under 10 years are quite possible.
Just take a 10kWp system as an example, which produces 10,000kWh per year. You install it on your roof for €13,000 (just taking some figure, photovoltaics have become quite cheap nowadays).
With full feed-in without self-consumption, the system pays for itself after 16 years – not great, but then there is still yield from a paid system.
With 20% self-consumption, you save at €0.30/kWh external electricity costs. So you save €600 per year on electricity costs and feed in for another €648. The system then pays for itself after just over 10 years. If electricity costs rise, you are under 10 years. If you have higher self-consumption, you are under 10 years.
The photovoltaic system is the only investment in a house that actually pays off financially (in my example, you have an investment of €13,000 and over 20 years a yield of €25,000). An ETF may be better, but please don’t say that a photovoltaic system does not pay off at all.

Does anyone actually have experience with infrared or electric surface heating, are they more effective than storage heaters?

I don't have specific experience, but I quickly googled a bit. For storage heaters, only about 30-40% of the electrical energy can apparently be converted into heat energy. With electric direct heaters (which include infrared and electric surface heaters), you are probably close to 100%. Heat pumps are even more efficient (because they extract part of their energy from the environment).

If a complete conversion to water-based radiators/floor heating/wall heating is not an option, air-to-air heat pumps might still be an option. (? Reservations see next paragraph) These are basically modern air conditioners (as a split air conditioner with an outdoor unit. It’s called "multisplit" if one outdoor unit serves several indoor units), which can also heat. They lose efficiency at negative outdoor temperatures, but at positive temperatures they can apparently reach over 200% (don’t quote me on that) and are therefore especially efficient during transitional seasons. (You’d have to check exactly how they perform in the depths of winter again; I suspect they can still beat direct heaters though). In any case, better check everything yourself again.

I can’t say how well that works in poorly insulated houses. I could imagine it getting uncomfortable if the unit has to blow out too much warm air because too much heat escapes outside. It probably works better in well-insulated houses.