ᐅ Which type of storage tank is suitable for an air-to-water heat pump?

Hi,

how large should a domestic hot water tank be for an air-to-water heat pump? Is a separate buffer tank for the heating system necessary? I think I once read that ideally you should avoid using a tank at all, because only then does the air-to-water heat pump operate at maximum efficiency. Is that true or nonsense? What do you recommend? And does coupling it with a thermal storage tank connected to a wood stove make sense to support heating during winter?

Difficult to generalize without conditions – generally:

Hot water depends on the users – if you like to shower a lot, you will need more liters
No buffer tank for heating
No water jacket
Fireplace only if you like it – not for profitability reasons

So it would be for 2 people, and later on with children. From what I understand, ideally no buffer tank is needed because it acts like a hydraulic separator, which ultimately makes the system inefficient. Can someone confirm this?

We have a 270-liter (71 gallons) tank for two people. Keep in mind the size of the bathtub, as these rain shower heads also use quite a lot of water. If the storage tank is small, you need to heat it to a higher temperature to fill the bathtub fully while keeping the water pleasantly warm.

For this purpose, we have a button that heats the water once to 60°C (140°F). After 40 minutes, you can fill the bathtub, and the water is still very warm. Without this button, the storage tank is not sufficient, at least for our relatively large bathtub.

I would like to revisit this thread.

Our heating engineer recommends a 200-liter buffer tank for our 300-liter domestic hot water tank, reasoning that the heat pump will operate more efficiently and cycle less frequently. According to him, this is more efficient than using only a 75-liter buffer tank. However, I often hear that buffer tanks can reduce efficiency. Therefore, I am interested in your experiences. What seasonal performance factors have you achieved with buffer tanks?

If the heat pump is correctly adjusted, it will cycle no more than necessary even without a buffer tank (e.g., referring to hysteresis). The floor provides such a large thermal mass; compared to that, a 200-liter (53 gallon) storage tank is insignificant.