ᐅ Quote for photovoltaic system including battery storage – storage yes/no?

@Musketier have you read and understood my calculations regarding the storage tanks? What do your calculations show?

RotorMotor schrieb:

@Musketier did you read and understand my calculations regarding the storage systems?
What are your calculations like?

Yes. But you only assume a 10-year lifespan for the storage system and constant electricity savings of 20 cents. That’s of course a very one-sided calculation. However, there are providers who guarantee 70% storage capacity retention for up to 20 years, of course for an additional cost. They probably wouldn’t offer that if they didn’t have confidence in the system’s durability.
As I said, I can calculate both scenarios positively or negatively depending on which values I use for the variables.

If you compare this to the average return of an ETF World portfolio, then neither option really pays off, except possibly the small-scale balcony solar system.

nordanney schrieb:

Then just calculate with 20-25% self-consumption. What result do you get?

Of course, a system without storage somehow pays off due to self-consumption.
The question is whether it really makes sense to fully cover the roof.
The larger the system, the lower the proportion of self-consumption. While the first module probably provides 100% self-consumption, the last module may only add 2-3% additional self-consumption.

I have a hipped roof and the choice between 2 sides, 3 sides, or 4 sides.
Bigger also means more effort for scaffolding and additional inverter(s), etc.
Being fully covered also means exceeding 10 kW peak capacity (kWP), which reduces the feed-in tariff even further.
"Fully covering" may provide the absolute best yield, but from a cost-benefit perspective, in my view, it is probably not optimal.

Musketier schrieb:

Yes. But you are only assuming a 10-year lifespan for the battery storage.

You have to make some assumptions.
Ten years is a figure that is often cited; rarely is there a longer warranty.
But feel free to redo the calculation with 12 or 15 years if you want.

Musketier schrieb:

and not rising electricity prices, but a constant saving of 20 cents.

Yes, I wrote that financing costs should balance that out.
Both are around 3%, but of course, that’s also one of those uncertain factors.

Musketier schrieb:

There are also providers who guarantee 70% of storage capacity for up to 20 years, though naturally for an extra cost. They probably wouldn’t offer that if they weren’t confident it would last that long.

The fact that the extra cost exists clearly shows that they are not so certain!

Musketier schrieb:

As I said, I can calculate both options in favor or against, depending on the values I use for the variables.

You may be right, but with realistic assumptions, you almost always come to the conclusion that adding battery storage to a photovoltaic system reduces the overall profitability compared to a system without storage.
And, as mentioned, you should also always consider the environmental impact.

Musketier schrieb:

If you compare the average return of an ETF world portfolio, then neither option is profitable. At best, a small balcony system.

That is not a meaningful comparison.
Completely different asset classes, completely different risks.

Musketier schrieb:

Of course, a system without storage is somewhat profitable through self-consumption.
The question is whether it really makes sense to fully cover the roof.
The larger the system, the lower the share of self-consumption. While the first module probably yields 100% self-consumption, the last module might only add 2-3% more self-consumption.

There are quite good calculators and simulations for that.
You also have to consider that each additional module is cheaper.
You only need one connection, one inverter, etc.

Musketier schrieb:

“Fully covering the roof” may provide the highest absolute yield, but from a cost-benefit perspective, it probably isn’t optimal in my view.

The highest percentage return is probably from a self-installed small balcony system.
The highest absolute return likely comes from a full roof system (without storage).
Most seem to enjoy having both a full roof and full battery storage here.

RotorMotor schrieb:

You have to make some assumptions.
10 years is a common value found; rarely is a longer warranty offered.
But you can of course also calculate it again with 12 or 15 years.

Actually, there is a 10-year warranty. After that, it could break (which would be the worst case), or it might last an additional 10 years with some loss of performance.
Possibly only one module might fail.

RotorMotor schrieb:

Yes, I had written that financing costs should balance out.
Both are around 3%, but it’s also one of those parameters that is guesswork.

In my opinion, that only seems true because both are estimated at around 3%. While the interest effect decreases over time since repayments count against it, the effect of price increases continues to grow, and because the feed-in tariff remains constant, that effect becomes even more pronounced.
Based on the difference between electricity price and feed-in tariff, I calculated an effect of about 3.8% instead of 3%, if I’m not mistaken. After 20 years, the electricity price wouldn’t be 30 cents but 52 cents, and the difference would be 44 cents instead of 22 cents.
That’s just a rough estimate, so I might have made a mistake.

RotorMotor schrieb:

That’s not a meaningful comparison.
Completely different asset classes, completely different risk.

That may be true that it is a different asset class, but the investment period is about the same. That’s at least what I would consider doing with the money alternatively.

RotorMotor schrieb:

There are actually quite good calculators and simulations for this.
You also have to consider that every additional module is cheaper.
You only need one connection, one inverter, etc.

That may be true for the last module. But in between, you do have additional costs (I believe these are called step-fixed costs), for example, a second inverter or scaffolding for the fourth side.

RotorMotor schrieb:

The highest percentage return is certainly the self-installed balcony system.
The highest absolute return is probably the full roof (without battery).
Most seem to have the most fun with a full roof and a full battery.

I’m somewhere in between. 🙂

We have now lived in the house for 10 years. So far, I have preferred the guaranteed savings from extra loan repayments at 3% rather than a potential 3% return from the photovoltaic system.
That issue is finally coming to an end since the house is almost paid off. However, I don’t yet have the surplus funds to pay for a full roof with a large battery out of pocket.
I’m approaching 50. We have a 20-year cycle. Whether I’ll deal with this again at 70 is unknown at this point.

Here, costs of 10,000 euros are assumed for a 10 kW battery storage system. In reality, it only costs 4,000 euros. This makes the storage system absolutely worthwhile.

Similarly, there are people who pay for their PV system, with or without storage, out of pocket. Just like I do. Financing costs play no role in that case.

On the contrary, it brings me a 10 percent annual return on my invested capital, despite having a storage system.