What is a buffer tank?
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Stefano Fonseca ist Ingenieur für Energie und Umwelt mit über sechs Jahren Erfahrung in der technischen Gebäudeausrüstung (TGA). Er kombiniert technisches Fachwissen mit einer Leidenschaft für verständliche Kommunikation. Seit mehr als fünf Jahren schreibt er als freiberuflicher Redakteur über erneuerbare Energien und nachhaltiges Wohnen, insbesondere über Photovoltaik und Wärmepumpen.
Whether it's a heat pump, pellet heating or solar thermal energy — modern heating systems do not always work in sync with actual heat demand. This is where an often overlooked but crucial component comes into play. In this article, you will find out everything about the buffer tank.
What is a buffer tank?
A buffer tank is a heat accumulator that temporarily stores excess heating energy and releases it again when required. It ensures that heating systems work more efficiently by reducing heat losses and reducing the frequency of heat sources such as heat pumps or pellet boilers.
How does a buffer tank work?
A buffer tank absorbs hot heating water via a heat exchanger. It stores excess heat and releases it again when needed. This allows you to heat your house or treat hot water retrospectively without the heat source having to start. This creates a time balance between heat generation and consumption. As a result, your heating system has to cycle less frequently, which saves energy and at the same time extends the life of the system.
What types of buffer tanks are there?
There are four common types of buffer tanks, which differ in design and function. Each variant meets specific requirements and is suitable for different heating systems.
What is the difference between buffer tank and hot water tank?
A buffer tank stores heating water to support heat generation, while a hot water tank provides drinking water for daily use. The buffer tank is used to compensate for heating loads, and the hot water tank provides shower or rinse water that is always available.
How big should a buffer tank be?
For a single-family house, a buffer tank of 300 to 800 liters is usually sufficient. The exact size depends on the heating capacity. You should plan for around 30 to 50 liters of storage volume per kilowatt of heating capacity. For a heat pump with 10 kW heating capacity, you need a buffer tank of 300 to 500 liters. Larger storage systems make sense when heating wood or integrating solar thermal energy.
How much does a buffer tank cost?
A buffer tank for a single-family home usually costs between 800 and 3,000 euros. The price depends primarily on the size, construction and equipment. Simple models are significantly cheaper than storage systems with an integrated fresh water station or solar connection. There are also installation and connection costs. These are usually between 500 and 1,500 euros, depending on expenditure and system integration.
Here is an overview of typical costs:
What is the point of a buffer tank?
Buffer tanks have the following advantages:
Does every heat pump have to have a buffer tank?
Not every heat pump has to have a buffer tank, but it is recommended in many cases. Especially with air-water heat pumps, the buffer tank ensures uniform operation and protects against frequent cycles. If your heat pump is linked to a heat pump electricity tariff with blackout periods, the buffer tank ensures that enough heat remains available even during these breaks.
What is the purpose of a heating element in a buffer tank?
A heating rod in the buffer tank allows heating water to be reheated electrically, for example when the main heating system produces little heat. It is often used in combination with a photovoltaic system to use excess solar power. This allows you to increase self-sufficiency. Without a PV connection, however, this solution causes higher electricity costs.
When is a buffer tank worthwhile?
A buffer tank is always worthwhile when the heating system does not deliver heat continuously or when renewable energies such as solar thermal energy or heat pumps need to be used efficiently. It improves efficiency, ensures uniform heat transfer and extends the life of the heater. A buffer tank is particularly useful for systems with cut-off periods or fluctuating heat generation. For single-family homes with modern heating systems, it is now usually part of the standard equipment.
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