ᐅ Photovoltaic System for 120 sqm of Living Space – Should the Entire Roof Be Covered?
Created on: 25 Oct 2021 23:00
K
Kalibri
Hello everyone,
I am currently looking into expanding our planned photovoltaic system.
The standard total capacity is 3.75 kWp. I have been considering upgrading it to 5 kWp.
Now, browsing through the forum, I see many examples with 10 kWp and more.
Of course, it makes sense to cover the roof as much as possible, but the price is an important factor for us.
There are two of us living in a 120 sqm (1292 sq ft) home.
What are your experiences with achieving the best possible balance between cost and performance?
I am currently looking into expanding our planned photovoltaic system.
The standard total capacity is 3.75 kWp. I have been considering upgrading it to 5 kWp.
Now, browsing through the forum, I see many examples with 10 kWp and more.
Of course, it makes sense to cover the roof as much as possible, but the price is an important factor for us.
There are two of us living in a 120 sqm (1292 sq ft) home.
What are your experiences with achieving the best possible balance between cost and performance?
KingJulien26 Oct 2021 20:18konibar schrieb:
I tried it but found that the slope on the north side (relative to the direction of sunlight!!!) would have to be entered as a negative value. Are you sure? That would be problematic; then nothing would be correct. But PVSOL arrives at roughly the same result, as do the solar installers who use it.hampshire schrieb:
This is so unusual that I'm interested in your calculation method. How do you calculate? What assumptions are you making?Option: Everything on the roof: south-facing, 30 degrees, 36 sqm (388 sq ft) 2400 kWh annual self-consumption, mostly in the mornings and evenings, no consumption during the day
The photovoltaic system with battery costs a total of 25,000, according to the calculator produces 8000 kWh, I calculated 6/7 of that, resulting in a theoretical output of 6800 kWh.
I can theoretically feed in 4400 kWh
I estimate operating costs at 2% of the investment per year
The feed-in income can cover the operating costs
I would have offset my self-consumption after 20 years
If the system lasts that long or nothing else happens
It doesn’t make financial sense to me. Or am I missing something?
The advisor immediately dismissed a smaller system just for self-consumption.
The most expensive part is the labor. And whether they install 1 or 8 modules doesn’t make much difference... but it would have cost about 15,000.
H
hampshire26 Oct 2021 23:43Thanks for the summary.
I didn’t quite understand the parameters.
2400 kWh is a low annual consumption. Congratulations. Your house has a baseline load that runs continuously, but with such low yearly consumption, it should be quite small.
Does that mean 8 kWp?
What is the capacity of the battery?
The battery could easily be oversized for such low consumption.
25K seems quite high to me, even though the parameters aren’t fully clear. That seems to be the main issue.
Is this your conversion from kWp to annual yield? I don’t understand the 6/7 ratio.
Are you calculating the 6800 minus the 2200?
You won’t cover 100% of your self-consumption. It’s better to calculate with about 75%.
What feed-in tariff do you expect?
What purchase price are you using for electricity?
That’s a reasonable approach. The modules usually last 20 years without issues, but inverters and batteries are not guaranteed to last that long.
I didn’t quite understand the parameters.
Rumbi441 schrieb:
2400 self-consumption annually, mostly in the mornings and evenings, no consumption during the day
2400 kWh is a low annual consumption. Congratulations. Your house has a baseline load that runs continuously, but with such low yearly consumption, it should be quite small.
Rumbi441 schrieb:
The photovoltaic system with battery costs 25K all in, and according to the calculator, produces 8000
Does that mean 8 kWp?
What is the capacity of the battery?
The battery could easily be oversized for such low consumption.
25K seems quite high to me, even though the parameters aren’t fully clear. That seems to be the main issue.
Rumbi441 schrieb:
6/7 of that calculated results in a theoretical output of 6800.
Is this your conversion from kWp to annual yield? I don’t understand the 6/7 ratio.
Rumbi441 schrieb:
I can theoretically feed in 4400
Are you calculating the 6800 minus the 2200?
You won’t cover 100% of your self-consumption. It’s better to calculate with about 75%.
What feed-in tariff do you expect?
What purchase price are you using for electricity?
Rumbi441 schrieb:
I calculate operating costs as 2% of the investment per year
That’s a reasonable approach. The modules usually last 20 years without issues, but inverters and batteries are not guaranteed to last that long.
hampshire schrieb:
Is this your conversion from kWp to annual yield? I don’t understand the 6/7.In Germany, 85% is the standard factor used to convert kWp into kWh.
Rumbi441 schrieb:
The photovoltaic system with battery costs all in 25K That is definitely way too expensive for an 8 kWp system plus a sensible battery.
A sensible battery for this system would be a maximum of 5 kWh.
Realistic prices (net, excluding taxes) would be:
8 kWp system 10k
5 kWh battery 6k
Try calculating the cost-effectiveness using these parameters!
H
hampshire27 Oct 2021 00:09Zubi123 schrieb:
85% is the usual factor used in Germany to convert kWp to kWh.I recommend using PVGIS data for the calculation.These are the values the solar installer gave me.
A major factor was the labor and handling costs.
Yes, everything calculated on an annual basis.
6/7 (about 85%) represent the actual watts I would get. Car manufacturers also state 5 liters per 100 kilometers (about 47 miles per gallon) for city driving, but in reality, it’s usually a bit more.
I’ve seen the 6/7 figure mentioned somewhere before as well.
The coverage of self-consumption was the installer’s basis for the calculation, which is why there’s also a battery.
Okay, assuming I invest 16,000 (currency), the system would be paid off after 16 years based on the same expected performance.
A major factor was the labor and handling costs.
Yes, everything calculated on an annual basis.
6/7 (about 85%) represent the actual watts I would get. Car manufacturers also state 5 liters per 100 kilometers (about 47 miles per gallon) for city driving, but in reality, it’s usually a bit more.
I’ve seen the 6/7 figure mentioned somewhere before as well.
The coverage of self-consumption was the installer’s basis for the calculation, which is why there’s also a battery.
Okay, assuming I invest 16,000 (currency), the system would be paid off after 16 years based on the same expected performance.
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