Photovoltaic system - rough cost framework

How big should the system be? Is there an estimate? We consume about 2700 kwh/a.

Do you need to take out financing for the photovoltaic system (the title still says PC – maybe a few IT geeks will join in) or are you paying cash? You can quite easily calculate whether and how the system pays off. Currently, prices for a 10kWp system are around 1,200-1,300€ per kWp all in (please don’t complain, these are current average prices across the country – you can also find them compiled fairly well – if you look, you will find). So, about €12,000 investment. With this, you will currently cover about 20-25% of your own electricity demand – assuming an external electricity price of 33 cents, you save about 25 cents/kWh, so about €150 per year (estimated 600 kWh). Besides that, you will roughly feed in 9,400 kWh of electricity at 8.1 cents/kWh, so about €760 p.a. Together that is €910 per year – with a €12,000-13,000 investment, the system pays off after 13-14 years. Not so sexy, because you could also invest your money elsewhere in parallel. But now the variables come into play: - annual electricity price increase - heat pump - e-car Depending on how you calculate, the amortization will improve dramatically. For example, I have a self-consumption of 25%, so 2,400-2,600 kWh per year (heat pump and car). That already looks significantly better. And if the electricity price in 10 years is, for example, 50 cents/kWh, everyone who installed a photovoltaic system on their house today will be rolling with laughter. But what can happen? - performance losses over time, mitigated by performance guarantees of partially over 85% after 20 years - defects on the inverter, mitigated by sometimes very long warranty periods, but after 10 years the warranty/guarantee usually ends The "problem" with small systems like the one you named in your initial post are the anyhow-costs. The scaffolding and standstill time don’t care whether you slap 2kWp or 50kWp on the roof. And the installation or connection doesn’t take that much longer. Only with a small system are they proportionally very high per kWp. Finally, on the topic of storage. Here you have to calculate how expensive the stored electricity becomes or how much you consume from it. Currently, it looks like electricity from the storage is often even more expensive than if you get it from the grid. Therefore, I basically don’t calculate a storage anymore.

A relative just paid 19k for 4.2kWp, a 5kWh storage, and a new meter cabinet and thinks it's great.

But it's nice that the realization is slowly dawning here too that, for the average person, it is usually nonsense and only really pays off with a lot of luck if the system runs trouble-free for 20 years...
And after 15, 20 years, you're just breaking even, so you only really start saving money then.

In winter, you have the problem that the 4.2kWp hardly produces enough energy for a heat pump... and you usually charge the electric car in the evening, so via the storage. So you're charging a battery from a battery... efficiency-wise, a complete disaster.
And in summer, you don't even get rid of the energy, so you feed it in for 6(?) cents. Hooray...

[A relative just paid 19k for a 4.2 kWp system, a 5 kWh storage, and a new meter cabinet and thinks it's great.

But it's nice that even here the realization is slowly dawning that for the average person it is usually nonsense and only really pays off with a lot of luck if the system runs trouble-free for 20 years...
And after 15, 20 years you just break even, only then do you really save money.

In winter, the problem is that the 4.2 kWp hardly produces enough energy for a heat pump... and you usually charge the electric car in the evening, so via storage. So you charge a battery from a battery... efficiency-wise a complete disaster.
And in summer you can't get rid of the energy at all, so you feed it in for 6(?) cents. Hooray...
]
I also have relatives who took up an En*al offer and I don't dare to tell them what I think about it. Luckily, I was able to prevent it with my parents because I was informed in time.

In winter, even 12 kWp delivers almost nothing for the heat pump. You definitely shouldn't charge an electric car from the storage; that makes absolutely no sense.

At least 8.1 cents but also not worth mentioning.

That's why I already said in essence, a photovoltaic system is more a hobby than a business case. At least if you use a manageable time horizon for evaluation.

In times of crisis, it's a backup, similar to the tiled stove when electricity and gas prices soared and suddenly, despite the also increased wood price, you still came off comparatively much cheaper and had the security of "the house will be warm."

That's why I already said in essence that a photovoltaic system is more a hobby than a business case. At least if you use a manageable time horizon for the evaluation.

I find that significantly underestimated. Realistically, an unfunded system should break even after about 10 years. And it’s also good for the green conscience.

I find that significantly underestimated. Realistically, a non-financed system should break even after about 10 years. And it's also good for the green conscience.

However, with a non-financed system, you still have to deduct the interest you would otherwise earn on the invested money. And with a financed system, you have to add the interest for the financing.

And if the possible generation of non-fossil energy is not carried out, we must then also start to consider the costs left by environmental destruction and climate change. Because these are now mostly -ironically- borne by the state (all of us) and not included in the individual profitability calculations. This just leads to taxes having to be spent on it.