HVAC Guide for Seattle, Washington
Seattle's mild but damp climate means heating dominates, but recent heat waves have made cooling capacity increasingly important.
Climate Data
| Parameter | Value |
|---|---|
| ASHRAE Climate Zone | 4C |
| Summer Design Temp (1%) | 85°F |
| Winter Design Temp (99%) | 25°F |
| Average Electric Rate | $11.5/kWh |
| Cooling Dominant | No |
Unique HVAC Challenges
- Mild but long heating season
- Increasing summer heat wave demand
- Heat pump suitability for marine climate
Local Utilities
- Seattle City Light
- Puget Sound Energy
Frequently Asked Questions
What HVAC size do I need in Seattle, Washington?
For a typical 2,000 sq ft home in Seattle, you'll need approximately 3-4 tons of cooling (depending on insulation and home age). Use our AC Size Calculator with your specific home details for an accurate result.
What is the average HVAC cost in Seattle?
Average AC replacement in Seattle costs $4,000-8,000 for a 3-4 ton system. Furnace replacement: $3,500-6,500. Heat pump systems: $5,000-11,000. Prices vary by equipment brand, SEER rating, and installation complexity.
Do I need a heating system in Seattle?
Yes. Winter design temp is 25°F. A heat pump alone can handle most winter conditions in this climate.
Design temperatures are based on ASHRAE Handbook 2021 99% heating and 1% cooling design conditions. Actual conditions vary.