ᐅ Single-family home photovoltaic system with 30 kW capacity

Hello everyone,

Due to the current low prices of photovoltaic modules, I would like to purchase the photovoltaic panels, mounting system, inverter, and battery storage in advance.
Key details:
Single-family house in the district of Altötting, 2 adults, 2 children
Roof orientation: North/South
Roof area: 13.5 m x 6.7 m (44.3 ft x 22 ft)
Photovoltaic module size: 1.69 m x 1.0 m (5.5 ft x 3.3 ft)
=> 3 rows with 12 modules each => 36 modules per side
36 modules on the west side and 36 modules on the east side
Therefore, I plan to buy 72 modules (410 W each) in advance.

This results in approximately 30 kW.

The heating system is planned to be a heat pump with a hot water storage tank.
I estimate the annual consumption to be 4.5 kW because I also want to install 2 or 3 split air conditioning units.

My questions are:
Do you think 30 kW is oversized?
What size battery storage would you recommend?
Which inverter would you suggest?

Thank you in advance.

brandner1860 schrieb:

Do you think that 30 kW is oversized?

No – go for as much as you can.

brandner1860 schrieb:

What size battery storage would you recommend?

It depends on whether you can buy it yourself and just need an electrician for installation. If you buy it yourself, >10 kWh is fine. If through a company, probably not at all.

brandner1860 schrieb:

Which inverter would you recommend?

I can’t advise on which devices you need – one inverter won’t be enough. It depends on the system design.

Storage units and inverters must be compatible. Not every storage system works with every inverter.

Personally, I think very highly of the Huawei system. It offers some features that others don’t. My system has been running reliably for 2 years. Starting with the app, the Wi-Fi connection, the storage, and the inverter are scalable, meaning they can be expanded.

Additionally, the storage can be extended, and the system balances itself automatically. Other systems cannot do this. Furthermore, with the Huawei Back Up Box, you can make the system capable of backup power and islanding. The design and build quality are very high-end. I have always used Huawei phones, so it was a natural choice to go with the Huawei system. I can only recommend it. Everything else is rather niche. Maybe Fronius with BYD storage is an alternative, but that quickly doubles the cost.

Purchasing the components outright is a very good idea. Prices are at rock bottom and exempt from VAT (value-added tax) in Germany. There won’t be a better time to buy.

For a 30 kWp system, I would choose a 15 kW storage unit.

But you can calculate everything yourself. In winter, you won’t get any production from the roof, no matter how large your system is. That’s just how it is.

I have a 7.2 kWp system and a Huawei Sun inverter, a three-phase hybrid 6 KTL model, with a maximum output of 6 kW. That matches the peak output of the system. I generate about 5,000 to 6,000 kWh of electricity.

That is more than enough for me. Approximately 2,500 kWh is fed back into the grid because I cannot use it all. But why do you need such a large system? You can do that if you want, but it’s not necessary. You can just as well fill your garden with panels, build a photovoltaic garden fence, or install a carport with solar panels.

I have a similar setup planned for the roof. Almost 28 kWp on a gable roof with north and south-facing sides. Roof pitch is 23°.

The inverter can handle 25 kW (that’s more than enough) from SolarEdge. I also installed SolarEdge optimizers (highly recommended!).

I have two storage units: one with 42 kWh and one with 84 kWh.

The great thing about these is that they even have wheels and a steering wheel, so I can take them on vacation!

Thank you very much for your responses. I am leaning towards a 30 kW system with a battery storage of around 12-15 kW.

Since I installed photovoltaic systems in my youth, I only need an electrician for the connection.

I am just not sure which inverter and battery storage to choose.

Maybe something like this?
Inverter:
2x Huawei SUN2000-10KTL-M1 hybrid inverters, High Current Version (tepto.de)
And storage:
3x Huawei LUNA2000-5-S0 – battery pack 5 kWh (tepto.de)

However, the Huawei battery storage seems a bit expensive to me.
Alternative:
PYLONTECH Force H3 HV 400V LiFePO4 high-voltage battery energy storage system, 3x modules, 15.36 kWh (Photovoltaik.lichtex.de/)

A small tip: Since last year, I believe there have been some requirements from the grid operator to install a disconnect device for systems over 25kW. This allows them to prevent your power feed-in, for example during midsummer when there is too much electricity fed into the grid. When I looked into it, the components alone cost roughly €1000 and you also need space in the cabinet. So the question is whether it makes sense to go above 25kW...