Metric Republic / Energy & building physics / Heat Pump Design Capacity Calculator

Heat Pump Design Capacity Calculator

Estimate heat-pump design capacity from building heat loss, DHW allowance and reserve.

Updated September 2026

How it works

Estimate heat-pump design capacity from building heat loss, DHW allowance and reserve.

Formula:
Required capacity = (building heat loss + DHW allowance)·(1 + reserve).

Before you use the result: Check manufacturer output at the actual source/supply temperature design point.

Practical use

Use verified material data and project geometry. Treat results as planning estimates and compare them with the energy/thermal requirements that apply to the project.

Keep units consistent with the source information.
Use project-specific densities, pack sizes and coverage rates where provided.
Round purchasing quantities to supplier packaging and delivery rules.

How to use this calculator: Heat Pump Design Capacity Calculator

Estimate heat-pump design capacity from building heat loss, DHW allowance and reserve.

Quick workflow

Enter the project values from the latest drawing, specification or verified site measurement.
Check units, material properties, allowances and any code- or supplier-specific parameters before calculating.
Review the result together with the formula, assumptions and the related checks shown on this page.

Worked example

Example inputs: Design building heat loss [kW]: 10; DHW / additional allowance [kW]: 2; Design reserve [%]: 10.

Using the sample values built into the calculator, the calculation gives approximately: Required heat pump capacity: 13.2 kW.

What the result means

Calculation method: Required capacity = (building heat loss + DHW allowance)·(1 + reserve).

Before using the result: Check manufacturer output at the actual source/supply temperature design point.

Common questions

What does this calculator do?

Estimate heat-pump design capacity from building heat loss, DHW allowance and reserve.

Which inputs should I verify?

Key inputs to verify include: Design building heat loss [kW], DHW / additional allowance [kW], Design reserve [%].

Can I use this result for final design or ordering?

Use the result as a transparent planning or checking aid. Final design, code compliance, supplier selection and project-specific decisions still need to be verified where applicable. Check manufacturer output at the actual source/supply temperature design point.

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