Understanding AC Types & Efficiency
Different AC types offer varying levels of efficiency and cooling capacity.
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Central AC
Whole-house cooling system that uses a network of ducts. SEER ratings typically range from 13-21, with higher ratings indicating better efficiency. Ideal for homes 1,500+ sq ft.
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Window Units
Single-room cooling with EER ratings of 8-12. Best for rooms up to 650 sq ft. Lower initial cost but higher operating costs per square foot.
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Split Systems
Ductless systems with indoor and outdoor units. SEER ratings of 16-30. Excellent for zone cooling and retrofit applications. Up to 30% more efficient than ducted systems.
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Portable AC
Mobile units with EER ratings of 8-12. Suitable for rooms up to 500 sq ft. Requires venting through window or wall.
Technical Considerations
BTU Sizing Guide
- 150-250 sq ft: 6,000 BTU
- 250-350 sq ft: 8,000 BTU
- 350-450 sq ft: 10,000 BTU
- 450-550 sq ft: 12,000 BTU
- 550-700 sq ft: 14,000 BTU
- 700-1,000 sq ft: 18,000 BTU
Efficiency Ratings Explained
SEER (Seasonal Energy Efficiency Ratio): Measures cooling output during a typical cooling season divided by energy used in watt-hours. Higher SEER means better efficiency.
EER (Energy Efficiency Ratio): Measures efficiency at a specific temperature (95°F). Used primarily for window units and portable ACs.
Energy Consumption Factors
- Climate zone and average temperature
- Insulation quality (R-value)
- Window efficiency (U-factor)
- Air infiltration rates
- Internal heat gains
Cost-Saving Features
- Variable-speed compressors: 30-40% more efficient
- Smart thermostats: 10-15% energy savings
- Zoning systems: 20-30% reduction in cooling costs
- Regular maintenance: 15-20% efficiency improvement
Advanced Cooling Concepts
Heat Load Calculation
Total heat load (BTU/hr) = Basic Load + Additional Loads
- Basic Load: Square footage × 20 BTU
- Additional Loads:
- Windows (south/west): +10% per window
- Sunny climate: +10%
- Each person: +400 BTU
- Kitchen: +1,200 BTU
Energy Consumption Formula
kWh = (BTU/hr × Hours Used) ÷ (SEER × 1000)
Where:
- BTU/hr = Unit's cooling capacity
- Hours Used = Operating time
- SEER = Seasonal Energy Efficiency Ratio