ᐅ Planning to install solar panels – options: 19 kW peak, 25 kW peak, 30 kW peak, battery storage?

Good morning everyone,

We are planning to install a photovoltaic system, and I have finally received a first offer. At the moment, everyone seems very busy, as out of three requested providers, only one responded after several weeks. Compared to the many threads here, the price seems a bit high, but this is somewhat offset by the fact that installation could theoretically still take place in April (depending on the module selection, see below).

I am aware of the basic discussion about whether or not to include a battery storage system. The offers I received all include storage systems for now.

Local conditions:
Flat roof with nearly 230 sqm (2,475 sq ft) of usable area, completely unshaded.
Previous year’s consumption: 12,800 kWh – 8,300 kWh measured by heat pump meter, 4,500 kWh household meter.
I recently got an electric car, and I expect an additional annual demand of around 4,000 kWh.
Expected yield: 900 kWh per kWp.

Offered options:

Available modules, same price with identical total output:
Hyundai HiE-S410VG (only available again from May)
Solarwatt Classic H1.1 Pure 375 (in stock with the provider)

Optional storage systems:
E3DC S10X 14 kWh
E3DC S10E Pro 19.5 kWh

Complete system offers (net):
19.68 kWp – €22,828
+ 14 kWh storage €13,250
Optional 19.5 kWh storage €18,630

24.6 kWp – €27,552
+ 14 kWh storage €13,250
Optional 19.5 kWh storage €18,630

According to the provider, 30 kWp could also be installed on the roof, but this would require a ripple control receiver. This option is available on request.

My questions:
- Are these offers still reasonable or overpriced?
- Does it make sense to choose the slightly “weaker” Solarwatt modules that are available now? Considering the current situation, is it better to have “a bird in the hand than two in the bush”?
- Is a battery storage system advisable given our relatively high consumption and low feed-in tariff? Mathematically probably not, but given the recent trends in the energy market, could it be a worthwhile investment for greater independence and peace of mind?
- Is it worth having a controllable wallbox (E3DC Connect)? It seems to be included in the offer but not separately priced. I already have a CEE32 socket in the garage and charge with a Juice Booster at up to 22 kW (missed out on the wallbox subsidy, so I got approval from the grid operator for 22 instead of 11 kW).

My reasoning: If I can achieve around 60% self-sufficiency with the storage, I would save €2,380 per year at the current electricity price of €0.31/kWh (31c/kWh). This means the “smaller” system with 19.68 kWp and 14 kWh of storage would pay for itself in 18 years, excluding feed-in and maintenance costs.

I find the photovoltaic offers quite fair to affordable given the current market and the quick implementation. However, the storage system seems very expensive at that price and should be significantly cheaper if you want one. For example, check the prices of the popular BYD storage systems online. If the storage price is quoted net, then all the more so.

Regarding the storage: the offered storage capacity tends to be too large for the size of the proposed photovoltaic system.

If the two modules cost the same, then you will use less roof space for the final output. So clearly go for the better modules and possibly expand later. The statement about 30 kWp is incorrect; you can install up to 29.99 kWp without any special regulatory requirements. If that fits, build based on your electricity consumption. The question is how much can fit on the roof in total? One option is to calculate whether >30 kWp is still worthwhile despite the extra effort, or b) to install a larger inverter and expand the system after 13 months.

A storage system is only worthwhile if you can reclaim the VAT (which is only possible with a full purchase of the photovoltaic system, not as a retrofit) and if there is a subsidy available (usually at the regional/state level) and the price is right. Economically, a storage system becomes viable depending on future price development at a purchase price of around €500/kWh (about $540/kWh) after all deductions. You are far from that.

I have no input on the wallbox. However, this should not be overestimated because when will your photovoltaic system deliver more than 22 kW? With your current offers, never; with 30 kWp on a few sunny days in midsummer around midday.

PS: I have 28.35 kWp (east/west) and 10.2 kWh storage.

Obermuh schrieb:

8300 kWh heat pump meter

What kind of house do you heat with that? At first glance, it sounds like poor insulation, a huge house, or a poorly configured heat pump.

Oetzberger schrieb:

What kind of house are you heating with that? Sounds like poor insulation, a huge house, or a poorly adjusted heat pump.

250 sqm (2700 sq ft) flat-roof bungalow, monolithic construction (36.5cm (14 inches) Poroton) with an open courtyard, so lots of exterior walls and window areas (e.g., 5x 5m (16x16 ft) lift-and-slide door). With hot water circulation. It doesn’t help that my wife insists on taking hot baths 3-4 times a week 🙄

Fuchur schrieb:

I find the solar PV offers quite reasonable to affordable in today’s market with a quick installation. However, I think the battery is too expensive for that price; it should be significantly cheaper if you want one. For example, check the popular BYD batteries online. If the battery price is net price, then even more so.

Regarding the battery: the offered battery tends to be oversized for the size of the proposed solar PV system.

If the two modules cost the same, you’ll occupy less roof space for the output. So, clearly better modules and possibly expand later. The statement about 30kWp is wrong—you can install up to 29.99kWp without any regulatory requirements. If it fits, build accordingly to your consumption. The question is, how much actually fits on the roof? One could a) calculate whether >30kWp makes sense despite extra effort or b) install a larger inverter and expand the system after 13 months.

A battery only really pays off if you can claim the VAT (which only works with a complete PV system purchase, not retrofitting) and also get a subsidy (usually on regional level), and the price is right. Economically, a battery will pay off depending on further price developments at a purchase price around 500€/kWh after all deductions. You’re far from that.

I can’t comment on the wallbox. But don’t overestimate it—when will your PV system deliver more than 22kW? With your current offers, never; with 30kWp on a few summer days around midday.

PS: I have 28.35kWp (east/west) and a 10.2kWh battery myself.

Thanks for the feedback. So, tend to go for maximum output on the roof area.

Normally, I charge the car at the lowest power I can set (about 2.6 kW) because it’s better for battery health, but I can increase up to 22 kW if I need faster charging.

Obermuh schrieb:

250 sqm (2700 sq ft) flat-roof bungalow, monolithic construction (36.5 cm (14 inches) Poroton blocks) with an open courtyard, so many exterior walls and window areas (e.g., five 5 x 5 m (16 x 16 ft) lift-and-slide doors). With hot water circulation. It doesn’t help that my wife insists on taking hot baths 3-4 times a week 🙄

36.5 cm (14 inches) Poroton sounds like a relatively new build. Still, the heat pump’s consumption is way too high. Normally, you might expect around 4000, maximum 5000 kWh heating per year. Which heat pump do you have? Off you go to the pink forum then :-)

Obermuh schrieb:

Good morning everyone,

Hello.

A few things upfront: There is no limit at 30 kWp. You should always fully utilize the roof space. Systems are getting cheaper, and with your consumption, 100 kWp is still too small. You need a ripple control receiver from 25 kWp, but it doesn’t hurt to have one (apart from the one-time cost of around 300 euros). This way, nothing gets curtailed.

If the house connection only allows 30 kVA, you can easily install 40 kWp on a flat roof and limit the inverter to 30 kVA. If you talk to the right people, the grid operators will know this as well. There are practically no losses since a flat roof never reaches maximum output.

Also important for flat roofs: You should always tilt the panels about 15° so they look like this: /\/\/\. Some should face east, others west. If space is limited, north-south orientation also works, with roughly the same yields. Why do this? At 15°, cleaning the panels is no longer necessary. If you install them completely flat, leave walkways free and make sure to go up at least once a year with a brush and garden hose!

SolarEdge is always too expensive and practically never necessary. In your case, definitely not necessary. The inverters are much too small anyway.

The module prices you mentioned are fair. Storage becomes economical at around €250 per kWh.

With your consumption and the planned system size, you can already achieve 50% self-consumption even without storage. (Payback without storage is about 10 years.) The more you consume, the less storage makes sense. If you have a controllable major consumer (heat pump and electric car), storage pays off even later. So forget about that.

EV charging: The lower the charging power, the higher the charging losses. I would therefore recommend charging with at least 6-11 kW. Most battery models can handle 50 kW or more, so you’re far from what could damage the battery. A controllable wallbox is mainly a convenience feature. Plug in in the evening, charging stops when the sun goes down and starts again when it comes up. I find this convenient. With a bit of effort, however, you can achieve similar results in other ways.