Economics of Photovoltaics - My Findings - Is Something Missing?

There are also reputable solar installers, see attachment, who provide a realistic calculation

An 8.82 kWp system was offered (pure south orientation with 28x 315 watt modules for €1132/kWp)

One likes to play with numbers and enjoys calculating, the other does not.

Well. Are you sure you have chosen the right contact person with me? What good is "enjoying calculating" if you use the wrong (or not all) numbers?

No, you save much more, in my sample calculation about €10,000 in 20 years, so about €500 per year.

Less your own invested time so far
Less the time to be invested annually
Less the tax advisor

In the end, not much remains of your (wrong/incomplete) calculated numbers.

You simply assume so many factors (variables), but you can easily miss by 30% up or down.

Fast payback or returns primarily have to do with a good and affordable offer :-p

Honestly, my motivation for a photovoltaic system is neither the environmental aspect nor the return. I just feel like using as much self-generated electricity as possible because I have an electric car. Whether it says -1% or +7% return over 20 years, I couldn't care less.

Dear toxixmolotow,

what do you think are the "wrong (or not all) numbers" or the "(wrong/not fully) calculated numbers" that I use?

Which points in my calculation do you think are wrong? Which aspects do you think are missing?

"You simply assume so many factors (variables)"

Yes, you have to make assumptions in calculations, after all, I provide a justification or source for each assumption and do not simply calculate without reason using a 5% electricity price increase or a 43% equity share. I also do not insist on decimal places in the return. Some solar installers have presented me with profitability calculations in which the return (after incorrect calculation) was specified as 13.16% accurate to two decimal places. That suggests that the profit after 20 years can be predicted precisely to 20 euros. I am also happy to repeat the calculations with other parameter values (less/more electricity price increase, less/more equity share, less/more yield, less/more maintenance costs) so that you get a feeling for how strongly the result can vary with different assumptions.

Regards

jx7

Hello,

whether I have overlooked important aspects

it’s not directly part of your calculation, but there is another aspect for the older among us who might have the chance to take early retirement with a golden handshake.

I work at the big German general store and during the last round of downsizing some former colleagues had the problem that they couldn’t easily accept the severance offers because they were not allowed to have any further income for that. This clause is of course designed so that people don’t just collect the severance here and then work somewhere else. Legally, however, it also prohibits income from solar systems.

By the time these issues were clarified, many deadlines had passed, by which they would have received several tens of thousands extra upon signing. They really swore quite a bit...

(I admit that my sympathy was limited, given the fact that just for accepting a part-time early retirement contract premiums in the range of 100-250k€ were paid....)

So, if you are in a large corporation and come of age around 60 to 65 during the funding period, such a system can really ruin your negotiating position...

Regards,
Andreas

Wrong/Forgotten Variables...

Just a few examples:

The insurance will probably cost around 100-120 euros.
The own consumption can also be 30% or 40%. Or only 15%. What about future technology? E-car? E-car at home during the day? Smart washing machine? Smart dryer? Or maybe the pool in the garden? With controlled residential ventilation, without controlled residential ventilation. 150W base load in the house or 350W? Who knows...

A practical example why an assumption does not fit:
We had 2200 kWh electricity consumption in the old apartment. In the house I calculated with 2600 kWh (+20%) plus 2200 kWh heat pump. So just under 5,500 kWh.

In fact, this year, so 2 years later, we are at 8,400 kWh, although the heat pump only needs 2200 kWh.

So... every calculation was obsolete.