Choosing the right heat pump is crucial for efficiency and comfort — but what happens if it isn't properly sized? A wrong decision can result in high costs and inefficient operations. Here you can find out how to correctly design a heat pump.

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How do I correctly design a heat pump?

You can correctly design a heat pump by using the Calculate the heat load of your building and adjust the output of the heat pump accordingly. The heat load indicates how much heat your house needs on cold days. It depends on the building insulation, the living space and the desired room temperature.

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This is how a heat pump is correctly designed:

1. Calculate heat load: Die Heat load calculation in accordance with DIN EN 12831 determines the heat demand of your building. A specialist company or energy consultant carries out this calculation. A rough estimate of previous gas or oil consumption is possible.
2. Define heat source: Depending on the size of the plot, soil conditions and structural conditions, an air, water or geothermal heat pump is an option. The choice influences output sizing.
3. Consider the heating system: Heat pumps work more efficiently with panel heating systems, which enable low flow temperatures. Existing radiators are being tested and may need to be adjusted.
4. Calculate hot water requirements: In addition to space heating, water heating must also be considered, as it increases the power requirement.
5. Observe efficiency values: A good heat pump has an annual performance factor (JAZ) of over 3.5 and is adapted to the climatic conditions of your location.
6. Use professional planning: An expert reviews the design based on individual building requirements and creates a detailed plan for an economical and efficient heat pump.

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Which factors determine the design of the heat pump?

The design of a heat pump depends on several factors that determine the heat demand of your building and the efficiency of the system.

• Building heat load: The heat load indicates how much heat your house needs on cold days. It is calculated in accordance with DIN EN 12831 and depends on insulation, living space and desired room temperature.
• Heat source: Air, water, or geothermal heat pumps have different performance requirements. The choice of source influences efficiency and the required sizing.
• heating system: Floor heating systems or large radiators work efficiently with low flow temperatures. Classic radiators require higher temperatures, which requires a more powerful heat pump.
• Hot water requirement: The energy required for water heating increases the overall output of the heat pump. Householders with high consumption require a more powerful system.
• climate zone: In regions with cold winters, the heat pump must provide sufficient heat even at low temperatures. The drop in performance in the event of frost must be included in the planning.
• Efficiency indicators: The annual performance factor (JAZ) and the coefficient of performance (COP) determine how efficiently the heat pump works. Good planning ensures optimal values.
• Building structure: Old buildings with poor insulation require more heat than new buildings. For older buildings, additional renovation measures, such as the addition of insulation, must be examined.

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What output does my heat pump need?

The required output of your heat pump is 30 to 100 watts per square meter of living space, depending on insulation and the desired room temperature. For a Single-family house with 150 m² living space Is the result of a heat pump output of 4.5 to 15 kW.

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How do I design the heat pump according to gas or oil consumption?

The required output of the heat pump can be roughly calculated based on previous oil or gas consumption. For this purpose, the annual consumption is multiplied by the calorific value of the energy source and divided by the operating hours of the heat pump. The following formula serves as a guide:

Required heating capacity = (annual consumption × calorific value)/operating hours

The assumed operating time of a heat pump is approximately 2000 hours per year. Here are two calculation examples for oil and gas heating systems:

• heating oil: Last year, a household has 2500 liters of heating oil consumed. The calorific value of heating oil is 10 kWh per liter. The heating output is calculated as follows: (2500 l × 10 kWh/l)/2000 h = 12.5 kW
• natural gas: A household has an annual consumption of 2000 m³ natural gas. The calorific value of natural gas is 10.3 kWh per cubic meter. The heating output is calculated as follows: (2250 m³ × 10.3 kWh/m³)/2000 h = 11.6 kW

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Why is the correct design of a heat pump important?

The correct design of a heat pump ensures efficient and cost-saving heating output. A heat pump that is too large results in high purchase costs and inefficient operation, while a heat pump that is too small does not provide enough heat and increases electricity consumption. Incorrect sizing can also shorten the life of the system.

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Common mistakes and their consequences

An incorrect design of the heat pump can significantly impair efficiency and lead to higher operating costs or technical problems. The most common mistakes and their consequences include:

• Missing heat load calculation: If the heat pump is not dimensioned based on a precise heat load calculation, it can result in undersizing or oversizing, which unnecessarily increases energy consumption.
• Too big a heat pump: Higher acquisition costs, inefficient operation and frequent clocking (switching on and off), which accelerates wear and shortens the life of the system.
• Too small heat pump: Not enough to heat the building on cold days, so a heating element must step in. This significantly increases power consumption.
• Wrong flow temperature: A heat pump works efficiently with low flow temperatures. Too high temperatures due to unsuitable radiators or lack of adjustments lead to inefficient operation and high electricity costs.
• Hot water demand not taken into account: If the hot water requirement is underestimated, the heat pump cannot supply enough energy, which leads to loss of comfort or frequent use of the heating element.
• Excluding the climate zone: In cold regions, a heat pump requires higher output. If this is not planned, the heating output may be insufficient on very cold days.
• Unsuitable heat source selected: An air-to-water heat pump can lose efficiency when outside temperatures are low. Failure to comply with this may result in high electricity costs.

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Which programs & calculators help with heat pump design?

There are various free online tools for calculating the appropriate heat pump output, such as Heat load calculator from the Federal Heat Pump Association (BWP). However, these calculators only provide initial guidance and do not replace a professional heat load calculation by a specialist company.

Specialized companies use software such as ours Autarc heat load calculation for precise heat pump design. With a detailed analysis of your building requirements, you get reliable planning for maximum efficiency and minimum heating costs.

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