The calculation of heating energy demand in Eturnity begins with the resource consumption of the existing heating system, which is either entered by the user or imported from the Eturnity heating calculator. To determine the actual heating energy demand required for the building envelope, the energy content of the resource (e.g., 2000 liters of oil) is corrected by the corresponding efficiency factors of the existing heating technology.

This process yields the annual heating energy demand, which is also displayed in the Eturnity Expert solution. The calculation ensures that hot water demand is correctly included in the overall calculation.

When the existing heating system configuration changes, the energy calculation automatically adjusts. For example, if an existing oil heating system uses an electric boiler for hot water production, and the new heat pump is designed to cover both heating and hot water generation, the necessary energy for hot water production is added to the heating energy demand.

The hot water energy calculation is based on the number of persons defined under Initial Situation > Building. This person count is also imported from the heating calculator data when a project is created via the heating calculator.

Eturnity AG uses the BIN methodology, also known as the frequency summation method, for calculating building heating power. This methodology is described in the standards DIN EN 15316-4-2 / ÖNORM EN 15316-4-2 / SIA 384/3.

The BIN method assumes a linear relationship between decreasing outdoor temperature and increasing heating power demand. The total heating energy demand is distributed across corresponding temperature BINs between the minimum and maximum temperatures prevailing at the specific location.

This distribution follows data from a TMY (Typical Meteorological Year) temperature profile for the corresponding location, with hourly temporal resolution. The result is a frequency summation structure that provides precise heating load distribution across different temperature ranges.

Within each BIN, conditions such as outdoor temperature, heating power, supply and return temperatures are assumed to be constant, enabling precise performance calculations for each temperature range.

In Switzerland, both the heating calculator and heating expert offer the option to switch the heating power calculation methodology to "Heat pump system module." This specialized calculation method incorporates SIA stations for enhanced accuracy in Swiss market conditions.

The heat pump performance calculation leverages the BIN methodology's constant conditions assumption. For each temperature class (BIN), the system determines the operating point and calculates:

The calculations use data points from the EN 14511 standard, which are extrapolated to the corresponding operating point. The annual energy demand and Seasonal Performance Factor (SPF) are determined by summing across all BINs.

Air-to-water heat pumps: Use the outdoor temperature of the corresponding BIN as the source temperature.

Ground source heat pumps: Use source temperature calculated according to the ground probe calculation methodology.

This approach ensures that each heat pump type operates with realistic source temperatures that reflect actual installation conditions.

Eturnity Heating Expert supports automatic calculation for probe length and arrangement, while allowing manual override at any time. The calculation follows the simplified calculation method of standard SIA 384/6.

The calculated ground probe length directly influences the source temperature calculation for ground source heat pump simulation. This integration ensures that:

For each heating system (existing reference system and new heating system), Eturnity calculates three cost components:

Amortization costs represent the costs allocated for heating system amortization, including equity capital costs (opportunity costs). This differs from investment costs, which represent the initial investment amount.

Annual amortization costs are calculated using the annuity formula, providing a standardized approach to comparing different heating technologies over their operational lifetime.

Energy costs are calculated by applying the defined inflation rate over the entire heating system lifetime to the first-year energy costs (defined under Economics > Heating System in Heating Expert). The total energy costs over the lifetime are divided by the lifetime to provide an expected average value.

This methodology ensures that energy cost calculations reflect realistic price inflation patterns over the system's operational period.

Maintenance costs are defined in Heating Expert under Economics > Heating System (excluding VAT). In the heating calculator, percentage definition based on investment sum is possible.

In Expert, maintenance costs can be influenced through "recurring costs" in the bill of materials, provided they are defined as "considered in economics."

Investment costs for the existing heating system are defined per kW in the project (Economics > Heating System), providing a standardized baseline for comparison calculations.

Investment costs for the new heating system are derived from the bill of materials minus any applicable subsidies. This approach ensures that:

For each energy resource, CO2 emissions per resource unit can be defined in the Eturnity solution (e.g., 2.650 kgCO2eq/liter oil). The entered or simulated resource consumption of existing and new heating systems is multiplied by emission factors and prepared in a customer-friendly format.

The CO2 calculation methodology enables:

This provides clear environmental justification for heating system upgrades while supporting sustainability goals.

Number of Persons: Flows into hot water demand calculation, which influences heating energy demand and can affect heating power requirements when the existing or new heating system is responsible for hot water preparation.

Building Type: Different building types have different typical hot water consumption patterns stored in the system. These are multiplied by the number of persons to determine hot water energy demand.

Construction Year and Energy Reference Area: In the heating calculator, these parameters generate appropriate estimated total energy consumption values for end customers. In Heating Expert, these parameters are purely informational and don't directly influence simulation results.

Heating Type: Determines the heating type for the existing system to be compared with the new system.

Hot Water Generation: Determines whether energy required for domestic hot water is generated by the main heating system and must be included in heating load calculation based on annual consumption data, or handled separately.

Supply and Return Temperature: Defines temperatures for the existing heating system. For heat pumps, supply and return temperatures significantly influence the Seasonal Performance Factor (SPF).

Heat Distribution: Defines heat distribution from the boiler/heat pump to living spaces. The choice of heat distribution influences supply and return temperatures.

Hot Water Storage: Influences energy demand and heating power calculation for existing system hot water. Larger storage systems create higher storage losses, leading to increased energy consumption.

Heating Energy Consumption: Serves as the primary basis for heating load calculation required for the new heating system and has the greatest influence on calculations.

Currently Installed Heating Power: This is purely informational data and has no influence on simulation results.

In the Heating System > Heating section:

This streamlined process ensures that all calculation parameters flow correctly from building analysis through system sizing to performance optimization.

For technical support, parameter customization, or questions about these calculation methods, please contact:

Eturnity Customer Support:support@eturnity.com