🕒 Annual Free Cooling Hours
💰 Annual Energy Savings
Savings Breakdown
Full Calculation Table
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How to Use the Economizer Calculator
Choose the Canadian city closest to your project for representative annual free cooling hour estimates, or select Custom if you have specific weather bin data.
Select dry-bulb or enthalpy control, then enter the changeover setpoint your economizer control sequence uses.
Enter the average cooling load your building carries during free cooling season and your local electricity rate.
Click Calculate Economizer Savings to see estimated annual free cooling hours, mechanical cooling energy avoided, and annual cost savings.
Understanding Air-Side Economizers
An air-side economizer brings in additional outdoor air beyond the minimum ventilation requirement when outdoor conditions can satisfy some or all of the building's cooling load without running the mechanical cooling system. In Canadian climates, where a large fraction of the year sits below typical indoor cooling setpoints, economizers can meaningfully reduce chiller or DX compressor runtime.
Dry-Bulb vs. Enthalpy Control
Dry-bulb control is simpler: it compares outdoor air temperature against a single fixed setpoint, typically 18 to 20 degrees Celsius for Canadian buildings, and opens the economizer whenever outdoor temperature sits below that value. Enthalpy control instead compares total heat content of outdoor air, including both temperature and humidity, against the return air condition, a comparison the enthalpy calculator can work out directly from temperature and humidity readings, which can be more precise but also more complex to commission and maintain correctly. Dry-bulb control is more common in Canadian commercial buildings given the generally lower humidity levels for much of the free cooling season compared to more humid climates.
Why Canadian Cities See So Many Economizer Hours
Vancouver's mild, temperate climate keeps outdoor temperature below typical changeover setpoints for a large fraction of the year. Prairie and interior cities like Calgary and Edmonton see fewer total economizer hours than Vancouver but still substantial opportunity given how cold and dry much of the year is relative to indoor comfort setpoints, a pattern that shows clearly in Environment and Climate Change Canada's climate normals for each city. Toronto and Montreal fall in between, with meaningful spring, fall, and even many summer nighttime hours available for free cooling.
Economizer Does Not Replace the Cooling System
The mechanical cooling system, whether a chiller plant or packaged DX unit, still needs to be sized for peak summer design conditions, since outdoor air alone cannot satisfy cooling load on the hottest days. The economizer's value comes from reducing compressor or chiller runtime during shoulder seasons and cooler summer periods, not from downsizing the mechanical system itself, though ASHRAE Standard 90.1 does set minimum economizer requirements for many system sizes regardless of the mechanical plant's own capacity. Confirm mechanical cooling sizing separately using the chiller plant calculator or RTU sizing calculator.
Waterside Economizers as a Related Strategy
Buildings with water-cooled chiller plants have an additional free cooling option through a waterside economizer, which uses cooling tower water directly through a heat exchanger to bypass the chiller compressor entirely during cold weather. This is a separate strategy from the air-side economizer calculated here; see the waterside economizer calculator for that specific analysis.
Commissioning and Sensor Accuracy Matter
Economizer savings depend entirely on the control sequence actually working as designed, which requires accurate outdoor air temperature or enthalpy sensors, correctly calibrated dampers, and a control sequence that properly modulates between minimum outdoor air and full economizer operation, exactly the kind of verification step a commissioning checklist is built to catch before occupancy. A poorly commissioned economizer can waste energy by bringing in excess outdoor air when it should not, or fail to open when conditions are favorable, so verification through commissioning is essential to realize the savings this calculator estimates.
Frequently Asked Questions
Dry-bulb control compares only outdoor air temperature against a fixed setpoint to decide whether outdoor air can be used for free cooling, ignoring humidity. Enthalpy control compares total heat content of outdoor air, including both temperature and humidity, against return air enthalpy, which can allow more free cooling hours in dry climates and fewer in humid climates compared to a simple dry-bulb setpoint.
A dry-bulb changeover setpoint of 18 to 20 degrees Celsius is common for Canadian commercial buildings using dry-bulb control, meaning the economizer can bring in up to 100 percent outdoor air whenever outdoor temperature is below that setpoint and above freezing protection limits. Enthalpy-based setpoints are typically expressed in kilojoules per kilogram of dry air rather than temperature alone.
Canadian cities spend a large fraction of the year at outdoor temperatures well below typical indoor cooling setpoints, which means outdoor air can satisfy cooling load directly without mechanical refrigeration for many more hours annually than a hot, humid climate would allow. Vancouver, with its mild year-round temperatures, and interior cities with cold, dry winters both see substantial economizer opportunity, though for different climatic reasons.
No. An economizer reduces mechanical cooling hours but does not eliminate the need for a cooling system sized for peak summer design conditions, since outdoor air alone cannot satisfy cooling load on the hottest days of the year. The economizer's value comes from reducing compressor or chiller runtime during the many hours when outdoor conditions allow free cooling, not from replacing the mechanical cooling system entirely. Confirm peak sizing with the chiller plant calculator.
Related HVAC Tools
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