Data Center Free Cooling Hours Calculator

Translate supply temperature, economizer approach, and weather-derived eligible hours into annual free cooling availability, accounting for maintenance deductions and operational readiness.

Target supply air or chilled-water temperature delivered to IT equipment.
Temperature lift between outdoor air or condenser water and the supply stream.
Annual hours where outdoor dry-bulb ≤ supply setpoint minus approach.
Defaults to dry-bulb hours when blank. Enter hours meeting wet-bulb or enthalpy criteria.
Optional. Hours per year when economizer operation is intentionally unavailable. Defaults to 0 h if blank.
Optional. Fraction of eligible time the economizer is ready. Defaults to 100% when blank.

Screening tool for thermal analysts. Validate results against detailed energy models and building automation trends before committing capital.

Examples

  • Supply 18 °C, approach 3 °C, dry-bulb hours 4,200 h, humidity hours 3,800 h, maintenance 120 h, availability 95% ⇒ Net free cooling 3,496.0 h/year (39.91% of 8,760 h) and 145.7 days of chiller offload.
  • Supply 16 °C, approach 2.5 °C, dry-bulb hours 3,100 h with defaults ⇒ Net free cooling 3,100.0 h/year (35.39% of 8,760 h) and 129.2 days of chiller offload.

FAQ

What weather data should I use?

Use site-specific metered weather or TMY/WYEC datasets binned to 1 °C increments so the dry-bulb and wet-bulb hour counts align with your economizer thresholds.

How do I choose the approach temperature?

Base the approach on tested performance of your plate heat exchanger, cooling tower, or dry cooler. Commissioning data or manufacturer curves provide defensible values.

Can I model partial economizer operation?

This calculator reports hours when ambient conditions fully satisfy the setpoint. Document partial-load blending separately by weighting hours with economizer and chiller sharing duty.

Additional Information

  • Result unit: hours per meteorological year with supporting temperature threshold and percentage of annual hours.
  • Default wet-bulb hours equal the dry-bulb tally when the humidity field is left blank.
  • Availability percentage is capped at 100% and multiplies the maintenance-adjusted hours.

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