Consultation for photovoltaic system

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

A small addition to my sermon above: Please pay very, very close attention to cloud tariffs and google them beforehand. Most tariffs are already bad from the start. The main problem, however, is that people build their 20-year calculations on them. Currently, one of the largest providers is canceling all its “good” contracts and thus destroying the calculations of thousands of customers who were previously talked into an extremely expensive giant storage as a cloud condition...

€250 per kWh will be difficult. The one I mentioned costs about €450 per kWh and installation is added on top of that. How do you come up with the triple rule for photovoltaic-storage? Does it mean if we install 13.29 kWp, the storage should have a maximum of 4.5 kWh?

If you want to operate it economically, yes. A brief explanation again (something from practice was already mentioned further above):

For economic viability, you need many cycles (empty-full-empty). For that, you need two things:
1) A storage that you can empty at night as much as possible throughout the year. So roughly standby consumption times 12 hours = storage size.
2) A photovoltaic system that refills the storage as much as possible every day. And that works much less often with a 1-to-1 ratio than with 3-to-1.

Personally, I would choose the ratio even larger (depending on roof area availability). Because if two electric cars and a heat pump (both standard in 10 years) are drawing from the photovoltaic system, only a few crumbs remain for the storage. So: Photovoltaic size matters!

...
For economic efficiency, you need many cycles (empty-full-empty). For that, you need two things:
1) A storage that you can preferably empty at night throughout the year. So roughly standby consumption times 12 hours = storage size.

no!
it is the other way around!

After the system has been purchased once, usage should be minimized:
each cycle absolutely causes wear/lifetime loss of the system.
Batteries deliver more energy amount/operating hours lifetime
if only half depth of discharge is used!

Although a single full cycle becomes proportionally cheaper in terms of resource usage,
in absolute terms only less energy amount comes out compared to half cycles!

Fictitious example:
with half cycles, a battery lasts 120 MWh, with full cycles only 100 MWh.

It is like with a car:
if I drive a lot – even pointless distances – the individual km naturally becomes proportionally cheaper.
But overall, per investment, it costs significantly more.

Partial charge around the middle wins!

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

Yes, for readers who do not deal with it more closely, it would be. The solar installer can also make the numbers look better.

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

And how many % of those who want a photovoltaic system have the time and experience?

Normal size: Normal size is a system when all roof surfaces (house, garage, carport) are fully covered

I am currently planning. If I cover everything, I come to about 24kWp on a fairly cheap roof. If you don’t make the numbers look better, you might just break even in about 20 years WITHOUT [EV]. And that’s always preached, it only has to pay off through [EV]. I’m just saying. You’re active in the photovoltaic forum, you know your stuff. That’s why you have to differentiate and not put € signs in people’s eyes.

no!
it's the other way around!

If one deliberately wants to buy a battery (for whatever reasons), then it should be designed in such a way that it yields maximum profit/minimum loss. You don't buy a 40-ton truck if you want to transport a single Euro pallet 100 km daily.

Of course, I don't want to advise anyone to draw as much as possible from the battery. In the end, even charging the e-car with it. That is nonsense in any case. It is only about the unavoidable power consumption at night. That's why I wrote "standby consumption." Every kWh not consumed is a good kWh.

It is true that batteries are spared if you don't fully exploit them. But this protection is already taken care of by the system itself. And as far as I'm concerned, you can oversize your battery by 20%. But since cells rarely die anyway, and instead the electronics usually fail, that is probably irrelevant!

Yes, for the reader who does not deal with it in more detail, definitely. The solar installer can also cook the numbers.

Ok.

And how many % of those wanting photovoltaic systems have the time and experience?

Very few. That’s why I didn’t write "pays off after 6-7 years," but rather 11-12 for turnkey systems.

If you don’t cook the numbers, you might just break even in about 20 years WITHOUT energy consumption.

And with energy consumption, it’s maybe about 11 to 12 years?!

I’m just saying. You’re active in the photovoltaic forum, know your stuff.

Recognized by the nickname?! That’s right, I’m interested and have read up a bit for a few weeks and got a lot of help. Others can do that too. How long do people inform themselves before buying a mid-range car?
(PS: I’ve already been warned twice (half a year late) because I referred to another place on the internet. Without a link. So you have to be careful.)

and not throw € signs in people’s eyes.

If it helps to encourage more people to get into photovoltaics, that method suits me. And in my opinion, I haven’t exaggerated... Anyone with a "normal" single-family house can achieve that. Even currently. And hopefully, things will look even better after the federal election.