ᐅ Heat pump combined with photovoltaic system, with or without energy storage

We are planning a new build with an air source heat pump. The electricity will come from our own photovoltaic system. Now the question arises whether a storage battery makes sense or not. The house is 10 meters (33 feet) wide and 14.5 meters (48 feet) long. The main apartment is on the ground floor. The attic will be partially converted into a one-person apartment. Later, we plan to have an electric car.
The installer gave us the following offer:

Heat pump Novelan 9-HSDV 12
Storage BYD Battery-Box Premium HVS 5.1 with Fronius Symo Hybrid 5.0-3-S
15 Trina Solar 340 TSM-DE06M.08 modules; some of the modules on the east side, some on the west side (house faces north-south)

Does this all make sense? Are these components compatible? Does anyone have experience with these brands?

Hello,
Whether the heat pump is suitable depends on the heating demand of the house. Are you considering the LAD 9 or LADV 9 model? The capacity seems quite generous to me, which is not always ideal for efficient operation. The LAD does not modulate, so oversizing it would be a disaster. The LADV would be the better choice in that case. However, at A7/35 it still has a minimum output of 2.74 kW. I can imagine that a smaller unit might be sufficient. What does the heating load calculation say?
A battery storage system for photovoltaic usually only pays off with a KfW 40 standard because then you reach KfW 40+ and the higher repayment grant covers the cost of the battery. At least, that was the case up to 2019. Things have changed since then, so you’ll need to look into that yourself again.
If you are building a KfW 40 house, the heat pump is definitely too large! (Or you are building a mansion)...

Cover the roof as much as possible, either fully utilize ≤9.9 kWp or >12 kWp, and skip the storage system.

For the heat pump, make sure it is the right size and not oversized; careful planning is essential here.

Heidi, I also have a similar system with a battery LG ESS 12.8 kWh, and I have been living in the house since summer 2018. My advice: install photovoltaic panels facing east and west. That way, when the sky is bright, you get solar power from early morning until late evening. If possible, run the air-to-water heat pump only when there is photovoltaic yield. If you can get a substantial subsidy for the battery, go for about 10 kWh. If there is no subsidy and your financial resources are limited: prepare the space and meter cabinet for a battery, but install it only in 5 to 10 years. Why? These systems are still in the experimental phase, quite inefficient, and especially very expensive. You won’t find electricity as expensive as the power from your own battery (without subsidies) anywhere in Germany, not even with the priciest default energy tariff. If you’re planning to buy an electric vehicle soon, you will basically have a huge battery in your garage anyway…

I was always skeptical about batteries, but in the end, we ordered our solar power system with a battery. You really need to calculate carefully. Above all, the solar system should be large enough to charge it properly because otherwise, there won’t be much input during winter. No one knows what will happen with the Renewable Energy Act. During the COVID-19 pandemic, it’s not a priority, and it’s increasingly likely that no new regulation will come into effect before the cap is lifted, which would mean there is no guaranteed compensation anymore. Then self-consumption (with a battery) is the only option.

The note about retrofitting is correct. However, you can only reclaim VAT on the battery when purchasing the system initially—not with a retrofit.

What convinced us were the falling prices, the tax refund, and a state subsidy program. This way, the 11.2 kWh (11.2 kWh) battery only effectively costs us 4300€. And we have (soon) almost 29 kWp (29 kWp) on the roof. That way, the heat pump can still draw some power in winter.

We also have an air-to-water heat pump combined with photovoltaic panels and a battery storage system. I connected my heat pump to the photovoltaic manager, and it works really well. We have 7.5 kWp (kilowatt peak) on the roof and a BYD HV 7.7 kWh (kilowatt hour) battery in the basement. The system has been operational since November 2019. During the transitional seasons, the electricity from the battery fully covers our needs because I heat the house and hot water during the day, so the heat pump doesn’t run at night.

Be careful with subsidies: not every combination of photovoltaic panels and battery storage qualifies for funding. Also, not every combination is eligible for tax deductions! Subsidies often come with additional restrictions—for example, instead of receiving support for 70%, it may be reduced to 50%!