The Question We Hear Every Summer
“I want a heat pump, but what about when it hits 105°F in Walnut Creek? Will it keep my house cool?”
Short answer: Yes. Modern heat pumps handle 100-110°F heat waves just fine—often better than older traditional AC systems.
Long answer: Let’s look at real performance data from our Bay Area installations during the brutal summer heat waves of 2022, 2023, and 2025, when Livermore hit 115°F, Walnut Creek reached 110°F, and even San Jose saw multiple 105°F+ days.
Understanding Heat Pump Technology
Heat Pumps ARE Air Conditioners
First, let’s clear up a misconception: A heat pump IS an air conditioner.
In cooling mode, a heat pump operates identically to a traditional AC:
- Same refrigeration cycle
- Same compressor technology
- Same cooling capacity
- Same SEER efficiency ratings
The only difference: Heat pumps can reverse the cycle to provide heating. They’re AC units that work both ways.
So when someone asks “Can a heat pump cool as well as an AC?” the answer is: It IS an AC.
Modern Heat Pump Advantages
Today’s high-efficiency heat pumps actually have cooling advantages over basic AC units:
Variable-Speed Technology:
- Adjusts capacity from 25-100%
- Runs longer at lower speeds
- Better humidity control
- More consistent temperatures
Advanced Refrigerants:
- R-410A performs better in extreme heat
- Some newer models use R-32 (even better high-temp performance)
Larger Heat Exchangers:
- Premium heat pumps have oversized coils
- Better heat rejection in extreme temperatures
- Maintains efficiency when it’s hottest
Smart Controls:
- Weather-adaptive algorithms
- Predictive cooling
- Optimized defrost cycles (heating mode)
Real Bay Area Performance Data
We’ve installed over 300 heat pumps across the Bay Area since 2020. Here’s what actually happened during extreme heat events.
Case Study 1: Livermore - 115°F (July 2022)
Home Details:
- 2,400 sq ft, built 1998
- Moderate insulation
- West-facing exposure (brutal afternoon sun)
- System: Carrier Infinity 20 heat pump (20 SEER, 10 HSPF)
Performance during 115°F outdoor temperature:
- Indoor temp maintained: 72°F
- System runtime: 18 hours/day (cycled, not continuous)
- Supply air temp: 56°F
- Temperature rise indoors: Never exceeded 73°F
- Homeowner comfort: “Never noticed it struggling”
Energy use:
- Peak day: 42 kWh
- Cost at PG&E rates: $25.20
- Comparable to their old 14 SEER AC: Same consumption
Verdict: ✅ Performed flawlessly
Case Study 2: Walnut Creek - 110°F (September 2023)
Home Details:
- 2,800 sq ft, two-story, built 1985
- Poor attic insulation (common for era)
- Upstairs bedroom heat gain issue
- System: Carrier Comfort 18 SEER/9.5 HSPF heat pump
Performance during 110°F outdoor temperature:
- Downstairs maintained: 74°F (target 73°F)
- Upstairs maintained: 76°F (target 74°F)
- System runtime: 20 hours/day
- Some short-cycling during peak (2-4 PM)
- Temperature overshoot: 1-2°F during hottest hours
Homeowner report: “Better than our old AC. The upstairs used to hit 80°F on these days. Now it stays comfortable.”
Follow-up action:
- We added attic insulation (recommended during install)
- Next heat wave: Perfect 74°F upstairs
Verdict: ✅ Good performance, improved with insulation upgrade
Case Study 3: San Jose - 107°F (August 2025)
Home Details:
- 3,200 sq ft, open floor plan
- Excellent insulation (2018 build)
- Lots of south-facing glass
- System: Carrier Infinity 24 heat pump (24 SEER)
Performance during 107°F outdoor temperature:
- Indoor temp maintained: 71°F (target 70°F)
- System runtime: 14 hours/day (variable-speed advantage)
- Supply air temp: 54°F
- Never exceeded setpoint
- Humidity maintained: 45-50% (excellent)
Energy use:
- Peak day: 38 kWh (3,200 sq ft home!)
- Cost: $22.80
- 35% less than estimate for equivalent SEER AC
Homeowner quote: “I was skeptical about heat pumps in San Jose summers. This thing is incredible. Runs quieter than our old AC and the upstairs finally matches the downstairs temperature.”
Verdict: ✅ Exceptional performance
Case Study 4: Pleasanton - 108°F (June 2025)
Home Details:
- 1,900 sq ft, single story
- Standard insulation
- System: Carrier Performance 16 SEER/9 HSPF (budget model)
Performance during 108°F outdoor temperature:
- Indoor temp maintained: 75°F (target 73°F)
- System runtime: 22 hours/day (near-continuous during peak)
- Temperature overshoot: 2°F during 3-6 PM
- Recovered to 73°F by 8 PM
Analysis:
- System slightly undersized (wanted to save money)
- Performed adequately but maxed out
- Still better than no AC!
Homeowner satisfied: “We knew we went smaller to save $2,000. It keeps us comfortable enough, and we can always go to 76°F on the hottest days.”
Verdict: ⚠️ Adequate performance (undersized system)
Case Study 5: Concord - 112°F (July 2023)
Home Details:
- 2,600 sq ft, poorly insulated 1970s home
- Single-pane windows
- Dark roof
- System: Properly sized 18 SEER heat pump
Performance during 112°F outdoor temperature:
- Indoor temp maintained: 77°F (target 74°F)
- System runtime: Continuous during peak hours
- Temperature crept up 3°F during hottest period
- Recovered overnight
Root cause: Home envelope issues, not equipment
- 30% of cooling lost through poor insulation
- Windows radiated heat
- Attic reached 155°F
Solution:
- Recommended attic insulation upgrade
- Window film on west-facing windows
- Attic ventilation improvement
After improvements: Next heat wave: Maintained 74°F easily
Verdict: ✅ System performed to spec; home needed improvements
Why Modern Heat Pumps Handle Extreme Heat
1. Rated for High Temperatures
Industry Testing Standards:
- AC units tested at 95°F outdoor temp
- Heat pumps tested at same 95°F standard
- Both must maintain capacity and efficiency
Premium models exceed standards:
- Carrier Infinity series: Rated to 115°F
- Maintains 90%+ capacity at 110°F
- Tested in Arizona and Nevada (hotter than Bay Area)
2. Variable-Speed Compressors
Traditional AC (single-stage):
- 100% on or 0% off
- Short cycles in moderate heat
- Runs constantly in extreme heat
- Less efficient
Modern heat pump (variable-speed):
- Adjusts 25-100% capacity
- Runs at 40-60% most of the time
- Ramps to 100% during peak heat
- More efficient overall
- Better humidity control
Real-world advantage: Variable-speed heat pumps often outperform single-stage ACs in extreme heat because they can modulate precisely to conditions.
3. Larger Coils and Better Heat Rejection
Premium heat pumps have:
- Oversized condenser coils
- Microchannel heat exchangers (more efficient)
- Larger surface area for heat rejection
- Better refrigerant flow design
Result: When it’s 110°F outside, these systems reject heat more effectively than standard AC units.
4. Advanced Refrigerants
R-410A (current standard):
- Excellent high-temperature performance
- Maintains pressure in extreme heat
- Better than old R-22 in hot weather
R-32 (newer models):
- Even better heat transfer
- Lower global warming potential
- Superior performance above 100°F
What About Even Hotter Days?
Performance Above 115°F
Heat pumps maintain cooling capacity up to 120°F, though efficiency drops slightly.
At 120°F outdoor:
- Capacity: 85-90% of rated
- Still plenty for Bay Area homes
- May run continuously during peak hours
- Temperature might rise 2-3°F during hottest period
Bay Area reality:
- We rarely see 115°F+
- When we do, it’s for a few hours
- Homes cool down overnight
- Not a persistent issue
Comparison to Traditional AC
Here’s the key insight: Traditional AC units face the exact same challenges in extreme heat.
At 110°F outdoor, single-stage AC:
- Also runs continuously
- Also sees capacity reduction
- Often struggles more due to on/off cycling
- No better than heat pump, often worse
At 110°F outdoor, variable-speed heat pump:
- Modulates to conditions
- Better humidity control
- More efficient operation
- Often superior performance
Proper Sizing is Critical
The #1 factor in heat wave performance isn’t heat pump vs. AC—it’s proper sizing.
Undersized System (Any Type)
At 105°F outdoor:
- ❌ Runs continuously
- ❌ Can’t maintain setpoint
- ❌ Temperature rises 3-5°F
- ❌ High stress on equipment
Properly Sized System
At 105°F outdoor:
- ✅ Cycles normally or runs steady
- ✅ Maintains setpoint ±1°F
- ✅ Comfortable home
- ✅ Normal equipment stress
Oversized System
At 105°F outdoor:
- ⚠️ Short cycles (wastes energy)
- ⚠️ Poor humidity control
- ⚠️ Higher upfront cost
- ⚠️ Less comfortable in moderate weather
Our Process: Every installation includes Manual J load calculation accounting for:
- Exact square footage
- Insulation levels
- Window types and sizes
- Orientation and sun exposure
- Inland valley climate data
- Design temperature for your city
Bay Area Climate Advantages
Why Heat Pumps Thrive Here
1. Heat Waves Are Brief
- 100°F+ days: 5-15 per year in valleys
- Usually 2-3 day stretches
- Cool nights (60-70°F) allow recovery
- Not like Phoenix with weeks of 115°F
2. Morning Cool-Down
- Pre-cool your home at 6-8 AM
- Take advantage of 65-75°F mornings
- Reduces afternoon load
- Smart thermostats automate this
3. Low Humidity
- Dry heat is easier to cool than humid heat
- Heat pumps more efficient in dry climates
- Less latent cooling load
- Better comfort at higher temperatures
4. Thermal Mass
- Many Bay Area homes: Stucco, concrete, tile
- Stores coolness from night
- Slower temperature rise during day
- Helps systems keep up
Maximizing Heat Pump Performance During Heat Waves
Before the Heat Wave
1. Pre-Cool Your Home
- Set to 70°F starting at 6 AM
- Build “cold mass” before peak heat
- Allows system to run efficiently when cool
2. Close Blinds and Curtains
- West-facing windows especially
- Reduces solar gain by 40-60%
- Biggest impact on afternoon temperatures
3. Check Air Filter
- Dirty filter reduces airflow 30%+
- Change before heat wave hits
- $5 filter = better performance
4. Clear Outdoor Unit
- Remove debris within 2 feet
- Ensure good airflow
- Trim bushes/plants
- Hose off coils if dusty
5. Verify Thermostat Settings
- Check schedule is correct
- Ensure fan set to AUTO (not ON)
- Smart thermostat: Enable eco mode
During the Heat Wave
1. Avoid Temperature Swings
- Don’t turn off during day to “save energy”
- Maintaining 76°F uses less energy than cooling from 85°F to 72°F
- Set it and forget it
2. Use Ceiling Fans
- Allows 3-4°F higher setpoint comfortably
- Fans use 50 watts vs. 3,500 for AC
- Counterclockwise for cooling
3. Minimize Heat Sources
- Cook outside or use microwave
- Run dishwasher at night
- Delay laundry until evening
- Turn off unnecessary lights
4. Strategic Setpoint
- 76-78°F during peak (2-6 PM)
- 73-74°F evening and night
- Reduces stress on system
- Still comfortable
5. Close Vents in Unused Rooms
- ⚠️ Only close 2-3 vents max
- Reduces load slightly
- Don’t close too many (damages system)
After the Heat Wave
1. Return to Normal Schedule
- Resume regular setpoints
- Resume normal operation
2. Monitor Performance
- Any unusual sounds?
- Is it cooling effectively in moderate weather?
- If concerns: Schedule checkup
3. Consider Upgrades
- Did you struggle to stay comfortable?
- Consider attic insulation
- Window film or replacement
- Seal air leaks
When to Call for Service
Normal heat wave behavior:
- ✅ Running 12-20 hours per day
- ✅ Indoor temp 1-2°F above setpoint during peak
- ✅ Cools down to setpoint by evening
- ✅ Supply air 15-20°F cooler than return air
Call us if you notice:
- ❌ Not cooling at all
- ❌ Temperature rising 5°F+ above setpoint
- ❌ Ice on outdoor or indoor unit
- ❌ Strange noises or smells
- ❌ Circuit breaker tripping
- ❌ Short cycling (on/off every few minutes)
Emergency service available: (510) 391-5597
Heat Pump vs. Traditional AC in Extreme Heat
Side-by-Side Comparison at 110°F Outdoor
Single-Stage AC (14 SEER):
- Capacity: 85-90% of rated
- Runtime: Continuous or near-continuous
- Humidity control: Poor (short cycles when able)
- Efficiency: Reduced
- Comfort: Temperature may rise 2-3°F
Two-Stage AC (16 SEER):
- Capacity: 90-95% of rated
- Runtime: High stage continuously
- Humidity control: Fair
- Efficiency: Better than single-stage
- Comfort: Maintains setpoint ±1°F
Variable-Speed Heat Pump (18-20 SEER):
- Capacity: 90-95% of rated
- Runtime: Modulates to exact need
- Humidity control: Excellent
- Efficiency: Best of the three
- Comfort: Maintains setpoint ±1°F
- Plus: Provides heating in winter
Winner: Variable-speed heat pump matches or beats traditional AC
Real Homeowner Testimonials
Livermore Installation (2022)
System: Carrier Infinity 20 heat pump
“We were nervous switching from our old gas furnace and AC to a heat pump. The first summer, we had that crazy 115-degree heat wave. I watched the thermostat nervously, expecting it to climb. It never budged from 72 degrees. I’m convinced this heat pump cools better than our old AC did.”
— Jennifer M., Livermore
Walnut Creek Installation (2023)
System: Carrier Comfort 18 SEER heat pump
“I asked the installer point-blank: ‘Will this keep up when it hits 108 in August?’ He said yes, but I was skeptical. We’ve been through two brutal summers now. The answer is absolutely yes. In fact, it’s quieter and more consistent than our old system.”
— David L., Walnut Creek
San Jose Installation (2025)
System: Carrier Performance 17 SEER heat pump
“Heat pump skeptic here—I thought they were just for mild climates. San Jose gets HOT. Did a ton of research and talked to Bay Area Climate Control. They showed me data from other installations. Decided to trust them. Best decision. Handles the heat perfectly and my gas bill is zero now.”
— Michelle T., San Jose
The Bottom Line for Inland Valley Homes
Can a heat pump handle San Jose/Inland Valley heat waves?
Absolutely yes—with proper sizing and installation.
Key facts:
- Modern heat pumps are rated and tested for 115°F+ operation
- Real Bay Area installations prove excellent heat wave performance
- Variable-speed heat pumps often outperform traditional AC in extreme heat
- Proper sizing matters more than equipment type
- Premium models maintain 90%+ capacity at 110°F
- Brief Bay Area heat waves are ideal conditions (vs. sustained Phoenix heat)
The real questions are:
- Is your system properly sized? (Manual J calculation)
- Is your home well-insulated? (Attic insulation critical)
- Do you have good windows? (Single-pane is your enemy)
- Is the system professionally installed? (Makes huge difference)
Answer yes to these, and your heat pump will handle anything the Bay Area throws at it.
Ready to Make the Switch?
Free Heat Pump Assessment
We’ll provide:
- Manual J load calculation for your exact home
- Heat pump options sized for inland valley heat
- Real performance projections for 105°F+ days
- Comparison to your current system
- Available rebates (up to $10,000)
- Honest assessment of your home’s readiness
Call Bay Area Climate Control: (510) 391-5597
Online: Request Free Assessment
Serving Inland Valley Communities:
- Livermore & Tri-Valley
- Walnut Creek & Concord
- San Jose & South Bay
- Pleasanton & Dublin
- All East Bay valley cities
We’ve installed 300+ heat pumps in the hottest parts of the Bay Area.
We know exactly what works in your climate.
Frequently Asked Questions
Q: What’s the hottest temperature a heat pump can handle?
A: Modern heat pumps are rated to 115-120°F. They maintain 85-90% capacity at these extreme temperatures. The Bay Area rarely exceeds this.
Q: Will my heat pump run constantly during a heat wave?
A: During peak hours (2-6 PM) on a 105°F+ day, yes—it may run continuously. This is normal and expected. Traditional AC would do the same. The system will cycle normally in morning and evening.
Q: Should I get a bigger heat pump to handle heat waves better?
A: No. Oversizing causes problems 95% of the year (poor humidity control, short cycling, wasted energy). Proper sizing handles heat waves fine and performs better year-round.
Q: Do I need backup cooling for extreme heat days?
A: No. A properly sized heat pump is your complete cooling solution. No backup needed.
Q: How does a heat pump compare to my current AC in 110°F heat?
A: Modern heat pumps perform as well or better than traditional AC at any temperature. The refrigeration technology is identical; premium heat pumps often have better components.
Q: What SEER rating do I need for inland valley heat?
A: Minimum 16 SEER. We recommend 17-20 SEER for best efficiency and performance. Variable-speed models (18+ SEER) provide the best comfort in extreme heat.
Q: Will a heat pump make my electricity bill skyrocket during heat waves?
A: Your cooling costs will be similar to a traditional AC of equivalent SEER. If you’re replacing an old 10-12 SEER AC with an 18 SEER heat pump, your costs will actually decrease 30-40%.
Q: What if my heat pump can’t keep up during a heat wave?
A: Call us immediately. This usually indicates undersizing (rare with our Manual J process) or home envelope issues (insulation, air leaks). We’ll diagnose and fix it.
Schedule Your Assessment Today
Bay Area Climate Control
Carrier Factory Authorized Dealer
Phone: (510) 391-5597
Emergency: 24/7 Available
Online: Request Service
Service Area: Alameda • Contra Costa • San Francisco • San Mateo • Santa Clara Counties
Your comfort during Bay Area heat waves is our specialty.