The Energy Recovery Effectiveness Calculator helps determine how efficiently a system can recover energy, typically in ventilation or heating and cooling systems. It calculates how close a real system gets to its maximum theoretical energy recovery. This tool is widely used in HVAC design, energy engineering, and environmental control systems. It belongs to the Thermal and HVAC Efficiency Calculator category.
This calculator is essential for evaluating the performance of energy recovery ventilators (ERVs), heat exchangers, and similar systems. A high effectiveness score means the system is performing well and conserving more energy, leading to lower utility costs and a reduced carbon footprint.
Formula of Energy Recovery Effectiveness Calculator
Effectiveness (ε) = Actual Energy Recovered / Maximum Possible Energy Recovery
Detailed Breakdown:
Effectiveness (ε)
A ratio between 0 and 1 (or 0% to 100%) that describes how well a system captures and reuses energy.
Actual Energy Recovered
This is the measured amount of energy the system transfers, commonly expressed in joules (J), kilowatt-hours (kWh), or British Thermal Units (BTU).
Maximum Possible Energy Recovery
This is the maximum energy that could be recovered if the system were perfectly efficient, calculated using ideal temperature and flow conditions.
Alternate Formula for Air or Heat Exchangers:
ε = (T_out − T_in) / (T_supply − T_in)
Where:
- T_out is the temperature of the air after energy recovery
- T_in is the temperature of incoming fresh air
- T_supply is the temperature of the exhaust or return air that supplies energy
This version is especially useful for HVAC applications using temperature readings rather than direct energy measurements.
Quick Reference Table
Here is a table that shows common values used in heating and ventilation recovery systems. This makes it easier to understand performance levels without full calculations:
| System Type | T_out (°C) | T_in (°C) | T_supply (°C) | Effectiveness (ε) |
|---|---|---|---|---|
| Residential ERV | 18 | 10 | 24 | 0.57 (57%) |
| Commercial Heat Exchanger | 20 | 12 | 28 | 0.5 (50%) |
| Industrial HVAC System | 23 | 15 | 30 | 0.53 (53%) |
| Passive Solar Heat Trap | 25 | 10 | 30 | 0.6 (60%) |
| Efficient ERV Design | 26 | 14 | 32 | 0.55 (55%) |
These values provide benchmarks to help users know whether their system is within expected performance ranges.
Example of Energy Recovery Effectiveness Calculator
Let’s calculate the effectiveness of a ventilation system.
Measured temperatures:
- T_in = 8°C
- T_out = 18°C
- T_supply = 26°C
Step 1:
Use the formula
ε = (T_out − T_in) / (T_supply − T_in)
ε = (18 − 8) / (26 − 8) = 10 / 18 = 0.56
This means the system is 56% effective at recovering energy compared to a perfectly efficient design.
Most Common FAQs
Most systems perform well if effectiveness is above 50%. High-performance ERVs can reach up to 70% or higher under optimal conditions.
Temperature differences indicate how much energy is transferred. The greater the difference, the more potential energy can be recovered.
Yes. By measuring effectiveness, you can identify underperforming systems and justify upgrades or improvements that save energy and reduce utility bills.