What You Can Calculate

Before buying equipment, you should be able to estimate three numbers: the heat recovered (kW), the effectiveness needed, and the simple payback period. The tools below help with each.

Spreadsheet Checklist

• Supply and exhaust airflow in m3/h or cfm
• Indoor and outdoor design temperatures
• Air density and specific heat (use 1.2 kg/m3 and 1.006 kJ/kgu00b7K for air)
• Electricity price and annual operating hours

Core Formula

Recovered power Q = m_dot * cp * DeltaT * effectiveness, where m_dot is mass flow. For a 10,000 m3/h stream at a 20 K difference and 70 percent effectiveness, that is roughly 46 kW of heating load removed from the fresh-air load.

Online Calculators

Our comparison and sizing pages embed the same formulas so you can change inputs and watch the payback move. Use the spreadsheet when you need to document the calculation for an audit or a client report.

Common Mistakes

• Using peak airflow instead of the part-load average
• Forgetting fan energy added by the extra pressure drop
• Ignoring frost protection energy in cold climates