Operate heat pump autonomously with photovoltaic system.

Hi, my attempt at an answer below. Best regards Thorsten

- Combination KFW 153 + 275 possible?

I think so, but you should definitely ask again just to be sure.
275 = KFW40+ subsidy?

- Grid feed-in max. 50% realistically feasible? What happens, for example, in summer if the feed-in increases?

Either the system regulates via the inverter or the grid operator throttles. I would have the inverter throttle. Excess power then goes into the battery (ideally with intelligent charging management) or use as much as possible yourself.
Proper system sizing is key here. Depending on location and orientation, roof pitch, type of collectors used, inverter efficiency, battery and much more. An expert must calculate.

For me, it is (very soon, installation starts tomorrow) throttled at 70%.
My system has charging management, but I only have a very small battery in a "smart solution" from SMA. This solution aims for a self-consumption rate of about 50% and uses the battery very intensively with high efficiency, in good irradiation sometimes more than 1 charge cycle/day.

- Are the common inverters and batteries already designed for the new requirements?

Yes. Those from quality providers are. This is not rocket science.

- Time value replacement guarantee 10 years, is this already considered by the manufacturers?

I don’t understand exactly what is meant here.
There are a variety of guarantees of different kinds, which vary from manufacturer to manufacturer in type and scope.

I do not understand exactly what is meant here. There are a variety of guarantees of different kinds, which vary in type and scope from manufacturer to manufacturer.

According to the guidelines from 01.03., precise requirements are set here, as quite a few things have changed since then. My question actually aims at whether anyone has already dealt so deeply with the topic to be able to say with certainty that there are currently batteries that meet the new guidelines for KFW 275 or whether it will take some time until manufacturers have adapted to it.

Furthermore, from my perspective, I would also like to present the topic of economic efficiency again, especially for builders who build according to the new KFW guidelines from 01.04.2016 onward. Assuming that the house I am offering corresponds to KFW 55 and that I need heating anyway, these costs are simply present. With the subsidy of €10,000 for KFW, I can finance the additional insulation. And now to the actual point:

For Kfw 40 + I get another €10,000. For that, I install a 6kW system on the roof and a corresponding storage unit in the basement, total costs €20,000. Please do not take these numbers literally; they are just meant to roughly represent the finances.

Up to this point, the fun costs me €10,000. Assuming an annual consumption of 5000kWh and an annual performance of the system of 5000kWh, the following picture emerges, for example:

Electricity costs without photovoltaics: 5000kWh/a * €0.25/kWh = €1250/a

with photovoltaics:
Self-consumption 2500kWh, saving 2500kWh/a * €0.25/kWh = €625/a
Feed-in 2500kWh, earnings 2500kWh/a * €0.12/kWh = €300/a

According to this calculation, I would have €925 more available per year; how long it then takes until the battery is paid off can be calculated individually. In this case, a battery is absolutely cost-effective if it functions correctly without damage, or am I completely mistaken?

Hello everyone,

I would like to revisit the topic of KFW 40+ here, deviating from the actual headline.
I am currently also planning a new build; the current offer describes a KFW55 house (140 sqm + 40 sqm basement granny flat + 20 sqm living basement = ~200 sqm living space, air-water heat pump).
Since the house is offered as KFW55, I would currently receive a €12,000 grant from the L-Bank. For a KFW40, it would be another €10,000 more; according to my provider, the additional insulation would have to be included. For KFW 40+, another €10,000 grant would be added; with this money, I could at least finance the photovoltaic system (~5-6KW) and possibly already part of the battery.

However, since 01.03.2016 there are new guidelines for the KFW Program 275; unfortunately, I have not found many discussions about this yet, so the following questions:
- Combination KFW 153 + 275 possible?
- Grid feed-in max. 50% realistically feasible? What happens, for example, in summer when the grid feed-in is higher?
- Are the common inverters and batteries already designed according to the new requirements?
- Time value replacement guarantee 10 years, is this already considered by the manufacturers?

153+275 does not work, according to Flose89.

For overproduction, it is best to plan a consumer for the summer. For example, an air conditioner. If that doesn’t help, put a space heater on the terrace?

To return to the topic of autonomy: Of course, it is absolutely not economical but certainly feasible.
A brine heat pump does not have such pronounced peaks in winter as an air-water heat pump and would probably be better suited.
A compact house with good insulation, plus photovoltaic with storage. In winter then heating with wood from your own forest when the power goes out.

Best to keep the room temperature at max. 18-19 degrees, lukewarm with little water or cold showers.

Regarding KfW 40+: Currently very profitable in Bavaria!

On the topic of KfW 40+: Currently very profitable in Bavaria!

I currently agree, especially for our construction project.

The additional subsidies make our KFW55 house into a KFW40+ house at no extra cost.

Regards

Can you break that down exactly for Bavaria?

10,000 Houses Program. 4,500€ Efficiency Bonus and 8,000€ for Photovoltaics with Storage.