Consultation for photovoltaic system

Sure, you can also just hang an immersion heater in the bathtub at night and wait until the tank is empty. Then you'll get enough cycles...

Here is my current energy balance for 2021. This is the total household consumption measured through one electricity meter. Behind this are the ground source heat pump for heating and hot water, controlled residential ventilation, as well as other household electricity. 14.4 kWP photovoltaics with a 10 kWh battery, no electric car, no fireplace:



The orange part of the consumption bars (above) represents the battery discharge. The annual totals are listed in the table below. You can see that the battery significantly increases the self-sufficiency rate. We only chose the battery because it qualified us for the Kfw 40+ subsidy (= €6,000) and additionally the state of NRW directly subsidized €2,000. Whether it would pay off without subsidies, I cannot say, but probably not.

You simply can't achieve the cycles needed to become at least somewhat profitable. And in the dark season, you can't fill the storage to benefit from it.

Calculating that it fits with 200-220 cycles, you can manage the unit, but it's just annoying when in reality you get a maximum of 100-120.

exactly,
and in both directions:

a "too large" battery does not pay off because you bought capacity that lies idle proportionally too much.
a "too small" battery undergoes too many (dis)charge cycles in a short time and is dead after 2...3 years.
Li-ion cells last about 500 full cycles (defined at 70% remaining capacity), depending on internal design and product series,
if they are never deeply discharged or overcharged.

if you take into account the respective service life, solar thermal becomes proportionally cheaper than is usually proclaimed.

The problem can be easily solved with an electric car ;)

But only if you charge it directly from the photovoltaic system. Using the home battery involves double the storage losses of 10-20%. That’s no fun either.

Li-ion cells last about 500 full cycles (defined at 70% remaining capacity), depending on internal design and product series,

Unfortunately, you forgot a 0 in the number of full cycles. It is calculated up to 7,000 full cycles (which then means significantly more smaller charges and discharges) up to a remaining capacity of 80%. There is no need to worry about that.

Unfortunately, you forgot a 0 in the number of full cycles. One calculates up to 7,000 full cycles (which then means significantly more smaller charges and discharges) down to a remaining capacity of 80%. There is no need to worry about that.

At 7,000 full cycles, you can just do a basic calculation for 1 kWh battery capacity: 7,000 * 0.9 kWh (on average 90% of the battery capacity) * €0.30/kWh (assumed average electricity price over the lifetime) = €1,890 This "back-of-the-envelope calculation" omits some parameters that would be important for an economic viability calculation, such as how long it takes to reach the 7,000 cycles (certainly not in 10 years for a private household) and whether the assumption of the electricity price holds true or not (it is probably higher), not to mention an interest consideration and the opportunity cost of feeding the energy into the grid. Let's calculate with 200 cycles per year and an average price of €0.35/kWh over 10 years 2,000 * 0.9 * 0.35 = €777 A net kilowatt-hour battery currently costs between €400 and €500 in the private customer sector. From this, it follows that one can make the battery look both good and bad financially – depending on the parameters one wants to use. Publicly accessible master data registers show that in the past 12 months, over 75% of photovoltaic systems between 5 and 15 kWp with storage have been applied for. Somehow, people seem to want the storage. My conclusion: There are some significantly more worthwhile investments and at the same time countless clearly worse purchases.