♻ Sensible Recovery Efficiency
💰 Annual Savings
Exhaust-Only vs. With Recovery
Full Calculation Table
| Parameter | Without Recovery | With Recovery |
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How to Use the Ventilation Energy Recovery Calculator
Enter the continuous ventilation airflow your HRV or ERV moves, available from the unit's rating or commissioning report.
Choose the sensible recovery efficiency that matches your core, or enter a custom value from the manufacturer's data.
Pick the nearest city for its heating degree-days, then enter annual operating hours and your cost of heat per kWh.
Click Calculate Savings to see the annual energy and cost recovered compared with exhaust-only ventilation and no heat recovery.
What Sensible Recovery Efficiency Actually Means
An HRV or ERV core transfers heat between the outgoing exhaust airstream and the incoming fresh airstream without letting them physically mix. Sensible recovery efficiency, often shortened to SRE, describes what share of that temperature difference the core actually transfers. A core rated at 70 percent SRE recovers 70 percent of the heat that exhaust-only ventilation would otherwise throw away, leaving the other 30 percent as heating load. Natural Resources Canada requires manufacturers to report SRE at 0 °C, and at −25 °C for units sold for colder design temperatures, so check the colder figure if your climate is cold, since this tool applies one SRE across the season.
How the Annual Energy Is Calculated
Warming outdoor air to indoor temperature takes about 1.2 W for every L/s of airflow per degree. Summed over a year, that gives kWh = 0.0288 × airflow (L/s) × heating degree-days, where Environment Canada defines a heating degree-day as the number of degrees the daily mean temperature is below 18 °C. The calculator scales that figure by your operating hours out of 8,760, then takes the SRE share as recovered. In the default example, 45 L/s in a 5,100 degree-day climate needs about 6,610 kWh without recovery. A 70 percent core brings that to about 1,980 kWh, recovering about 4,630 kWh worth about $601 at $0.13 per kWh.
Why This Calculator Compares Against Exhaust-Only
Exhaust-only ventilation, the simplest baseline, pulls stale indoor air out and lets replacement air in at full outdoor temperature, with zero heat recovery. Comparing an HRV or ERV against that baseline shows the full value of the heat exchanger itself, separate from any savings that might come from reducing airflow through demand-controlled ventilation, which the demand-controlled ventilation calculator covers on its own.
Climate Drives the Dollar Value
The same core and airflow rate recovers far more in Winnipeg or Edmonton than in Vancouver, because a prairie climate has roughly twice the degree-days of the coast. The city presets use approximate 1981 to 2010 heating degree-day normals, which differ by weather station within a city, so use the custom field for a specific site or a building-code design value. The degree-day calculator shows how degree-days are built from a balance point.
HRV vs. ERV for This Calculation
The sensible heat math here applies equally to an HRV and an ERV, since both transfer temperature between airstreams. An ERV's added value comes from moisture transfer, which helps maintain comfortable indoor humidity in winter and can reduce dehumidification load in summer, neither of which this sensible-only calculation captures. Size either core with the HRV calculator or ERV calculator.
Does the Higher-Efficiency Core Pay Back?
The result is a yearly saving, not a payback. To weigh it against the extra purchase price of a higher-efficiency core, divide the added cost by the yearly saving difference between the two cores, or use the payback period calculator. Fan electricity and defrost use reduce the net saving, and this tool leaves them out.
Confirming the Baseline Airflow
This tool assumes the airflow entered is correct for the home or zone. Confirm the required continuous rate with the whole-house ventilation calculator, and check that the system stays balanced once intermittent exhaust loads like bathroom fans are running with the balanced ventilation calculator.
Frequently Asked Questions
Without recovery, the heat needed to warm incoming air is about 0.0288 × airflow in L/s × heating degree-days (base 18 °C), in kWh per year, which comes from 1.2 W per L/s per degree over 24 hours. The core recovers its sensible recovery efficiency (SRE) share of that, and the rest is the heating load that remains. A 70 percent core on 45 L/s in a 5,100 degree-day climate recovers about 4,600 kWh a year.
Sensible recovery efficiency measures how much temperature-related heat the core transfers between the outgoing and incoming airstreams. Total, or enthalpy, recovery efficiency adds in moisture transfer, which only an ERV core provides. An HRV is rated on sensible recovery efficiency alone, since it does not transfer moisture between airstreams.
For sensible heat alone, a well-matched HRV and ERV often perform similarly, since both exchange temperature between airstreams in much the same way. An ERV's extra advantage comes from moisture transfer, which can reduce humidification load in winter and dehumidification load in summer, benefits that a sensible-only HRV does not provide.
Not always. The dollar value of moving from a moderate to a high recovery efficiency core depends on the airflow, the number of degree-days and the cost of heat, and a small efficiency gain on a small system in a mild climate may not pay back the added equipment cost in a reasonable time. Run the numbers for the specific airflow and climate before assuming a higher-efficiency core is the better value.