About this calculator This calculator evaluates the financial return on investment for an Energy Recovery Ventilator (ERV). Heating savings use heating degree days with the ERV's sensible effectiveness, since winter recovery is essentially all sensible. Cooling savings use a total-energy (enthalpy) calculation — average enthalpy difference, operational hours, and the ERV's total effectiveness — so latent (moisture) recovery is included. Both are corrected for air density at the selected weather station's elevation. Use it to justify ERV equipment costs to building owners or to compare ERV options with different efficiency ratings and price points.
Use when You need to evaluate the financial return of installing an energy recovery ventilator.
Variables
Outdoor CFM Ventilation airflow in CFMSensible Efficiency ERV sensible effectiveness % — drives heating savingsTotal Efficiency ERV total (enthalpy) effectiveness % — drives cooling savingsCooling Operational Hours Annual hours of cooling-season operationHDD Heating degree daysAvg Enthalpy Difference (Δh) Average outdoor-to-exhaust air enthalpy difference during cooling hours in BTU/lbOccupied Hours per Day Daily operating schedule — rescales HDD and cooling hoursHeating Fuel Natural gas or electric resistance heatElectricity Rate Electricity cost in $/kWhGas Rate Gas cost in $/thermIEER Cooling equipment IEER ratingAFUE Gas heating AFUE efficiency %Annual Maintenance Yearly ERV upkeep cost (filters, service) in dollarsAdded Equipment Cost Additional cost of ERV equipment and installation over a non-ERV system
ERV Specs
Outdoor Air CFM
Volume of fresh outdoor air supplied
Occupied Hours per Day
Building occupancy hours per day
Sensible Efficiency (%)
Typical range: 60-80%
Total Efficiency (%)
Typical range: 50-75%
Climate Data
Heating Degree Days (HDD)
Annual heating degree days for your location
Cooling Operational Hours
Annual hours of cooling-season operation
Avg Enthalpy Difference Δh (BTU/lb)
Typical range: 3-12 BTU/lb
Cost & Efficiency
Electricity ($/kWh)
Average electricity cost per kWh
Heating Fuel
Fuel used by the heating equipment the ERV offsets
Natural Gas ($/therm)
Average natural gas cost per therm
AFUE (%)
Gas heating efficiency (typical 80-98%)
IEER
Cooling equipment efficiency (typical 12-20)
Annual Maintenance ($/yr)
Added upkeep: filters and service
Added ERV Equipment + Installation Cost ($)
Only the additional cost of adding the ERV vs. a non-ERV system — not the full system cost

* Estimate only. Climate values autofilled from the selected weather station assume a standard 75 °F / 50% RH indoor condition and 24/7 operation unless Occupied Hours per Day is set (HDD uses the standard 65 °F base). Savings are corrected for air density at the station's elevation; without a station, sea-level air is assumed. Adjust any value to match your building and schedule.

Annual Heating Savings —
Annual Cooling Savings —
Total Annual Savings —
Simple Payback (years) —
10-Year ROI —

What is an energy recovery ventilator (ERV)?

An energy recovery ventilator (ERV) is a device that transfers heat and moisture between the building exhaust airstream and the incoming outdoor ventilation air, reducing the energy required to condition outdoor air. ERVs use an enthalpy wheel or plate exchanger to precool incoming air in summer and preheat it in winter. Sensible effectiveness ratings for commercial ERVs typically range from 60–80%, meaning the device recovers 60–80% of the temperature difference between the two airstreams. Latent effectiveness is typically 50–70%. The energy savings depend on climate severity and humidity, outdoor air volume, operating hours, energy costs, and ERV efficiency. Simple payback periods for ERVs in commercial applications typically range from 2–5 years depending on climate zone and energy rates. ASHRAE Standard 90.1 requires energy recovery for many air systems above specific outdoor air thresholds.

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