Bay Area Microclimates & HVAC

The Bay Area isn't one climate - it's many. Your HVAC needs depend on which county you're in.

Five Distinct Climates

Climate 1: Coastal Marine (San Francisco, Oakland, Berkeley)

Characteristics:

• Year-round 50-65°F temperatures
• Summer highs: 65-75°F
• Winter lows: 48-55°F
• Consistent fog and marine influence
• Humidity: Moderate-high

HVAC Impact:

• Minimal heating needed (2-4 months)
• Minimal cooling needed (2-3 months)
• Dehumidification important
• Heat pump ideal (2-3 months can be cold)

Recommended System:

• Heat pump: Best choice
• Mini-split: Perfect for efficiency
• Central AC: Over-capacity in coastal areas

Typical Sizing:

• 1.5-2 tons for 2,000 sq ft
• vs 3-4 tons in inland areas

Annual Energy Profile:

• Heating months: Oct-Mar (cool)
• Cooling months: Jul-Aug (mild)
• Comfortable months: Apr-Jun, Sep

Climate 2: Inner Bay (San Mateo, Hayward, Fremont)

Characteristics:

• Summer: 75-85°F (moderate)
• Winter: 45-55°F
• Less fog than coast
• Transition zone
• Humidity: Moderate

HVAC Impact:

• Moderate heating (4-6 months)
• Moderate cooling (3-4 months)
• Balanced heating/cooling needs
• Standard two-stage system works well

Recommended System:

• Heat pump or furnace + AC
• Both heating and cooling equally important
• Two-stage or variable-speed

Typical Sizing:

• 2-2.5 tons for 2,000 sq ft

Climate 3: Inland Valleys (Walnut Creek, Concord, Livermore, Pleasanton)

Characteristics:

• Summer: 90-105°F (hot)
• Winter: 35-45°F (cold)
• No fog protection
• Extreme swings
• Humidity: Low-moderate

HVAC Impact:

• Significant heating (5-7 months)
• Significant cooling (5-6 months)
• Needs capacity for both extremes
• Both furnace and AC heavily used

Recommended System:

• Heat pump with backup heat (dual fuel)
• Or separate furnace + high-capacity AC
• Variable-speed for efficiency in extremes

Typical Sizing:

• 3-4 tons for 2,000 sq ft (larger!)
• Undersizing = discomfort in both seasons

Climate 4: South Bay (San Jose, Cupertino, Mountain View)

Characteristics:

• Summer: 85-95°F (warm)
• Winter: 45-55°F (mild-cold)
• More heating than cooling
• Microclimate variations by elevation
• Humidity: Moderate

HVAC Impact:

• Moderate heating (4-6 months)
• Moderate cooling (3-4 months)
• Balanced but leaning heating
• Similar to Inner Bay

Recommended System:

• Heat pump or furnace + AC
• Modern heat pumps excellent choice
• Standard sizing

Typical Sizing:

• 2-3 tons for 2,000 sq ft

Climate 5: Peninsula (Palo Alto, San Bruno, Half Moon Bay)

Characteristics:

• Summer: 70-80°F
• Winter: 48-58°F
• Variable: elevation matters
• Coastal influence
• Humidity: Moderate-high

HVAC Impact:

• Mild heating and cooling
• Dehumidification important
• Heat pump excellent
• May be over-capacity issue

Recommended System:

• Heat pump (perfect fit)
• Mini-split for efficiency
• Standard sizing conservative

Typical Sizing:

• 1.5-2.5 tons for 2,000 sq ft

System Selection by Microclimate

Climate	Best System	Sizing	Heating Months	Cooling Months
Coastal	Heat pump	Small (1.5-2 tons)	2-4	2-3
Inner Bay	Heat pump/AC	Medium (2-2.5 tons)	4-6	3-4
Inland Valley	Dual fuel	Large (3-4 tons)	5-7	5-6
South Bay	Heat pump/AC	Medium (2-3 tons)	4-6	3-4
Peninsula	Heat pump	Medium (2-2.5 tons)	3-5	2-3

Real Examples

Oakland Coastal Home

• Climate: Marine
• Current system: 2.5-ton AC with gas furnace
• Optimal upgrade: 2-ton heat pump
• Why: Saves $3,000 on oversized equipment

Walnut Creek Home

• Climate: Inland valley
• Current system: 3-ton AC with furnace
• Optimal upgrade: 3.5-ton dual fuel (or all-electric)
• Why: Needs full capacity for 90°F summers and 35°F winters

San Jose Home

• Climate: South Bay
• Current system: 2.5-ton AC with furnace
• Optimal upgrade: 2.5-3 ton heat pump
• Why: Balanced heating/cooling needs, heat pump efficient

Winter Considerations by Zone

Coastal (SF, Oakland, Berkeley):

• Furnace or heat pump both work
• Heat pump sufficient for mild winters
• May occasionally use emergency heat (OK in mild zone)

Inland (Walnut Creek, Concord, Livermore):

• Cold winters require capable heating
• Dual fuel recommended for extreme cold
• All-electric OK with backup heat strips

South Bay (San Jose, Mountain View):

• Moderate winters, heat pump recommended
• Standard heat pump capacity sufficient
• Electric heating adequate for backup

Summer Cooling Load

Coastal areas:

• Rarely need AC running (3-4 weeks/year)
• Oversizing wastes money and energy
• Right-sizing saves thousands

Inland valleys:

• AC runs June-September (4+ months)
• Needs adequate capacity for 100°F+ days
• Undersizing = discomfort and high bills

Professional Load Calculation

Always get Manual J calculation:

• Accounts for microclimate
• Considers home location/orientation
• Factors in insulation levels
• Right-sizes for YOUR home

Don't use "rule of thumb" sizing (tons per sq ft)

Rebate Impact by Microclimate

Coastal (less heating needed):

• Heat pump qualifies for MORE rebates
• System pay-back faster (lower energy use)

Inland (more heating/cooling):

• Larger system = higher rebate potential
• Energy savings larger
• ROI excellent

Ready for Microclimate-Optimized System?

We'll assess your exact location and recommend perfect sizing.

Get Climate Assessment | Call (925) 578-3293