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Home Size

Choosing the Right Air-to-Water Heat Pump for Your Home Size

When it's time to select an air-to-water heat pump for your home, understanding the relationship between the size of your house and the size of the heat pump is crucial. An optimally sized heat pump will not only ensure your home stays warm and cozy but also that your energy bills remain manageable.

Understanding Heat Pump Sizing

Heat pump sizing is not a one-size-fits-all situation. It is determined by several factors including the size of your home, insulation quality, window type, construction year, and whether you have underfloor heating or other efficient heating distribution systems.

The size of a heat pump is generally rated in kilowatts (kW) and refers to its heat output capacity. The goal is to match this capacity to your home's heat loss, which is the amount of heat your home loses in a given time period. This match ensures that your home can be efficiently heated even during the coldest months.

Calculating Your Needs

To begin calculating your needs, you should consider the average energy requirements for homes in Central Europe, which can serve as a baseline. While the specific figures can vary, a well-insulated house might require approximately 50 to 70 kWh of heat per square meter per year for heating and hot water.

For a 150-square-meter home, this translates to a total annual heat requirement of about 7,500 to 10,500 kWh. To convert this to a daily requirement, divide by 365 days, which gives you a range of approximately 20.5 to 30 kWh per day.

Hot Water Considerations

For a home with four people, hot water needs must be added to this calculation. Typically, each person uses about 50 liters of hot water per day. A heat pump's efficiency, known as the Seasonal Coefficient of Performance (SCOP), plays a role here. For air-to-water heat pumps, a SCOP of around 3.5 is a reasonable estimate for Central Europe.

Article Scenario Examples

Now, let's look at two specific scenarios for a 150 square meter home in Central Europe, one being an older, retrofitted house with natural ventilation and the other a newly built house.

Scenario 1: Retrofitted Older House

  • Assume higher heat loss due to older construction, around 70 kWh/m²/year.
  • Annual heat requirement: 150 m² × 70 kWh/m²/year = 10,500 kWh/year.
  • Daily heat requirement: 10,500 kWh / 365 days ≈ 28.8 kWh/day.
  • For hot water: 4 persons × 50 liters × 365 days at an efficiency of SCOP 3.5.
  • Total annual requirement including hot water: approximately 12,775 kWh/year.
  • Recommended heat pump size with a buffer: 7 kW to 8 kW.

Scenario 2: New Build House

  • Lower heat loss, say 50 kWh/m²/year due to better insulation and modern construction.
  • Annual heat requirement: 150 m² × 50 kWh/m²/year = 7,500 kWh/year.
  • Daily heat requirement: 7,500 kWh / 365 days ≈ 20.5 kWh/day.
  • For hot water: Similar calculations as above.
  • Total annual requirement including hot water: approximately 10,275 kWh/year.
  • Recommended heat pump size with a buffer: 5 kW to 6 kW.

Simplified Calculation for Readers

To simplify this for our readers, here’s a quick guide to follow:

  1. Calculate your home's heat requirement: Multiply your home's size in square meters by the average kWh required per square meter per year (50-70 kWh for Central Europe).
  2. Add hot water needs: Estimate hot water usage for your family and add this to your annual heat requirement.
  3. Apply a SCOP: Divide the total annual requirement by the SCOP to get the effective energy needed from the heat pump.
  4. Determine size with a buffer: Choose a heat pump size that meets your daily requirement plus a buffer for colder days.

By following these steps, you can ensure that the heat pump you choose is neither too small, which would lead to insufficient heating and higher costs due to overworking the unit, nor too large, which would result in unnecessary energy expenditure and wear on the system.

All you need for heating your home