Bay Area Winter Heating Help Center
Every heating problem, from no heat to high bills, answered
Bay Area winters are mild on paper, which is exactly why heating problems catch people off guard. A furnace or heat pump that sat idle from spring to fall gets switched on for the first cold, damp night in November, and that is when igniters, flame sensors, pilots, filters and thermostats show what a summer of neglect did to them. This help center collects everything we know about keeping a Bay Area home or business warm and safe through winter.
Start with the symptom finder if something is wrong right now. Use the system guides if you want to understand what you have, whether that is a gas furnace, a heat pump, a ductless mini-split, an original wall or floor furnace, or an Eichler with radiant heat in the slab. Everything else, from tune-up checklists to PG&E bill help, renters' rights and the Bay Area's new rules on gas furnaces, is in the library further down. These guides come from Cool Aid Air Conditioning & Refrigeration, a family business in Santa Clara that has been fixing Bay Area heating since 1966.
- Safety first
- Symptom finder
- By heating system
- Winter calendar
- Bay Area climate
- All guides
- Renters
- Businesses
- By city
- FAQ
Safety first: stop here if any of these is happening
- You smell gas (rotten eggs or sulfur): leave now. Do not flip switches, use phones or start a car inside the garage. Call 9-1-1 and PG&E from outside.
- A carbon monoxide alarm is sounding, or people in the home have headaches, dizziness or nausea that ease outdoors: get everyone and every pet outside and call 9-1-1.
- You see flames, scorching or smoke at the furnace, a wall heater or a floor grate: shut it off only if it is safe to do so, get out and call 9-1-1.
- A loud boom when the burners light: turn the thermostat off and call a technician. Do not keep restarting it.
Step-by-step instructions: gas smell and carbon monoxide alarms. For a heating emergency that is not a gas or CO problem, our 24/7 line is 1-800-266-5243.
Symptom finder: what is your heater doing?
Find the card that matches what you see, hear or smell. Each one lists the safe checks you can make yourself, the point where a technician should take over, and the guide that covers it in full.
No heat at all
Try first
Thermostat set to Heat and a few degrees above room temperature; fresh batteries; breaker and furnace switch on; filter not clogged; furnace door fully closed.
Call a technician if
Everything checks out and it still will not start, or it starts and shuts off again.
Air from the vents is cold
Try first
Make sure the fan is set to Auto, not On. Give a heat pump a few minutes; it may be defrosting.
Call a technician if
Burners never light, or they light and go out.
Turns on and off every few minutes
Try first
Replace a dirty filter and open closed registers. Check the thermostat is not near a heat source or a draft.
Call a technician if
It keeps cycling with a clean filter, or you see a blinking error code.
Clicking, but no flame
Try first
Check the gas valve on the supply line is open and your other gas appliances work.
Call a technician if
It clicks and fails more than two or three times. Repeated attempts can let gas build up.
A boom or bang when it lights
Try first
Nothing. Turn the thermostat off.
Call a technician if
Right away. Delayed ignition means gas is building up before it lights.
Burning or dusty smell
Try first
A dusty smell for the first few minutes of the season is normal. Change the filter.
Call a technician if
It lingers, smells electrical or like burning plastic, or you see smoke.
Rotten-egg smell
Try first
Leave the building. Do not look for the leak.
Call a technician if
9-1-1 and PG&E from outside, before any HVAC company.
CO alarm chirping or sounding
Try first
A single chirp every minute or so is usually a low battery or an end-of-life alarm. A full alarm pattern means get out.
Call a technician if
9-1-1 for an alarm. A technician should inspect the furnace before it runs again.
Water on the floor by the furnace
Try first
Shut the system off at the thermostat, mop up and look for a disconnected or clogged drain line.
Call a technician if
Water keeps coming back, or it is near electrical parts.
Heat pump steaming or iced over
Try first
Steam and a short fan stop are the normal defrost cycle. Keep leaves, plants and stored items at least a couple of feet clear of the outdoor unit.
Call a technician if
Ice stays on the coil for hours or covers the whole unit.
Heat pump air feels lukewarm
Try first
Hold your hand at a register: heat pump air runs cooler than furnace air but should feel clearly warm.
Call a technician if
Rooms never reach the setpoint on a mild day.
Some rooms are always cold
Try first
Open every register, keep returns clear, and check for drafts at windows and doors.
Call a technician if
The same rooms stay cold even with the furnace running normally. Ducts are the usual cause.
Thermostat blank or ignoring you
Try first
New batteries, the breaker for the furnace, and the furnace door switch.
Call a technician if
It is still blank, or the system does not respond to it.
Wall or floor heater will not stay lit
Try first
Relight only by following the instructions on the heater's label.
Call a technician if
The pilot goes out again, or the flame is yellow and lazy instead of blue.
Heating bill doubled
Try first
Compare the same month last year and check your baseline and rate plan on your bill.
Call a technician if
Usage jumped without a cold snap. The system may be short cycling or losing heat through ducts.
Dry air, static or wet windows
Try first
Aim for indoor humidity between 30 and 50 percent; run bath and kitchen fans.
Call a technician if
You see mold, or the house smells musty whenever the heat runs.
Power went out
Try first
Gas furnaces need electricity too. Never heat with an oven, grill or generator indoors.
Call a technician if
The heat does not come back after the power does.
You rent and the heat is broken
Try first
Tell your landlord in writing, with the date, and keep a copy.
Call a technician if
Nothing is fixed within a reasonable time. Local code enforcement can inspect.
Help by heating system
Not sure what you have? Look at where the heat comes out and what sits outside.
Gas forced-air furnace
The most common Bay Area system: a furnace in a closet, garage, attic or crawlspace pushing warm air through ducts to floor or ceiling registers.
Central heat pump
An outdoor unit that looks like an AC but also heats, with an indoor air handler and ducts. More common every year as homes switch from gas.
Ductless mini-split
A heat pump with wall, ceiling or floor heads in each room and no ducts. Common in additions, ADUs and homes that never had ducts.
Wall or floor furnace
A gas heater built into a wall or under a floor grate, usually in homes built before the 1960s. Often has a standing pilot.
Radiant floor (Eichler)
Hot water pipes in the concrete slab, heated by a boiler. Classic in Eichler neighborhoods.
Electric baseboard and space heaters
Simple electric resistance heat. Reliable, but expensive to run and a fire risk when misused.
Commercial rooftop units
Packaged units on the roof of shops, restaurants and offices, often with a gas heat section.
A Bay Area winter heating calendar
What to do, and when, from the first cool nights of fall to the spring switch back to cooling.
| When | What to do |
|---|---|
| September to October | Book a heating tune-up before the first cold night. Replace the filter, test carbon monoxide and smoke alarms, and run the heat for a few minutes on a mild afternoon so a failure shows up before you need it. |
| October to November | First real cold nights. Expect a dusty smell for the first few minutes. If a pilot is out, PG&E offers free pilot relights and gas appliance safety checks (PG&E). |
| November to February | Wood-burning alerts are most common now, and a no-burn Spare the Air alert can be called on any day of the year (Spare the Air). Check before lighting a fire. |
| December to January | The coldest stretch, and the longest heater run times. Check the filter monthly. Clear leaves and storm debris from around outdoor heat pump units. |
| Storm season | Atmospheric rivers bring outages and flooding. Never heat with an oven, grill or generator indoors, and have any furnace that sat in water inspected before use. See outages and storms. |
| February to March | Compare your winter bills with last year. If usage jumped, the system may be short cycling or losing heat through ducts. A good time to plan a replacement before the next season, not during it. |
| April | Switch the thermostat to cooling, change the filter and book the AC check. See our seasonal HVAC guide. |
Why Bay Area heating problems are different
A Bay Area winter rarely looks severe on a weather map, but it is long, damp and uneven. The same January night can be mild by the Bay and close to freezing twenty miles inland, and homes built for mild weather often have little insulation, leaky ducts in unconditioned attics and crawlspaces, and heating equipment that sits idle for half the year. Those three things, not extreme cold, cause most of the heating calls we get.
| Area | Weather station | Average January low | January nights at or below 32°F | Freezing nights per year |
|---|---|---|---|---|
| San Jose | San Jose airport | 41.8°F | 1.4 | 3 |
| Livermore, Pleasanton, Dublin | Livermore airport | 37.8°F | 6.4 | 19 |
| Morgan Hill, Gilroy | Gilroy (nearest station for Morgan Hill) | 38.1°F | 5.4 | 16 |
| Walnut Creek | Concord Buchanan Field (nearest station) | 41.2°F | 3.6 | 8.5 |
| Bayside East Bay (Hayward, Fremont) | Oakland airport | 42.0°F | 1.1 | 2.6 |
| For comparison: San Francisco | Downtown San Francisco | 46.6°F | 0 | 0 |
NOAA 1991-2020 climate normals (NOAA NCEI). No official normals station exists for Walnut Creek or Morgan Hill, so the nearest stations are shown.
What that means in practice:
- Inland valleys get real frost. Livermore and Gilroy average well over two weeks of freezing nights a year. Heat pumps there spend more time in defrost, and a system that barely keeps up on a mild night will fall behind on a frosty one. See heat pumps in winter.
- The Santa Clara Valley and bayside cities are mild but damp. Freezing nights are rare, which is exactly why heat pumps work so well here, but long stretches of cool, wet weather keep a heater running for months.
- The state's building code agrees. California's energy code splits our service area across climate zones 3 (bayside), 4 (South Bay) and 12 (inland East Bay) (California Energy Commission), and the requirements for a new system differ between them.
Every winter heating guide, sorted by problem
New pages in this help center are marked. Everything else is an existing guide from our technicians, grouped so you can find the one you need.
Safety and emergencies
Gas leaks, carbon monoxide, fire risk and what counts as a real emergency.
- Gas smell and CO alarms
- Space heater safety
- Power outages and storms
- The Hidden Dangers of Old Heaters in Bay Area Homes
- Furnace Needs Repair? 7 Warning Signs
- When to Call for Emergency HVAC Repair: 10 Red Flags
- What to Do When Your HVAC Breaks at 2 AM
- 24/7 Emergency HVAC Repair Bay Area
- How 24/7 Emergency HVAC Service Works
Troubleshooting a furnace
Symptom by symptom, with what you can check safely and what needs a technician.
- No-heat checklist
- Pilot light and ignition
- Furnace short cycling
- Furnace noises
- Furnace leaking water
- Why Your Furnace Won't Turn On & How to Fix It
- Why Is Your Furnace Blowing Cold Air?
- Why Your Furnace Smells Like Burning (And How to Fix It)
- HVAC Not Heating or Cooling? Expert Repair Tips
- Why Is My HVAC System So Loud?
- 6 Warning Signs Your Furnace Needs Repair
- Top Signs You Need Furnace Repair in Fremont
- Common Heating Issues in Walnut Creek Homes
Thermostats
A surprising number of no-heat calls end at the thermostat. Check it first.
- Thermostat Problems Every Homeowner Should Know
- Why Your Thermostat Isn't Responding & Fixes
- How to Troubleshoot Your Thermostat Before Calling Help
- Smart Thermostat Guide: Nest vs. Ecobee vs. Honeywell
- Best Thermostat Settings to Save Energy
Heat pumps and ductless mini-splits
How they behave in winter, what goes wrong and how they compare with gas.
- Heat pump winter problems
- Top Heat Pump Problems & How Techs Diagnose Them
- 10 Common Mini-Split Problems & Their Causes
- Ductless Mini-Split Repair in the Bay Area
- Heat Pump vs Mini-Split: The Real Difference
- Heat Pump vs Furnace in the Bay Area: Cost & Comfort
- Top 5 Heat Pump Brands for Bay Area Homes
- 7 Benefits of Installing a Heat Pump in San Jose
Older homes and other systems
Wall heaters, floor furnaces, radiant slabs and the quirks of older Bay Area houses.
- Wall and floor furnaces
- Radiant heat in Eichler homes
- Seasonal HVAC Checkups for Older Homes
- Furnace Repair by Fuel Type: Gas, Electric & Oil
- Gas Furnace vs Electric Heating: Which Is Better?
Tune-ups and winter prep
What a tune-up should include, what you can do yourself and how often to change filters.
- Fall Furnace Checklist: 12 Steps Before Bay Area Winter
- Bay Area Furnace Tune-Up Checklist Before Winter
- Fall Furnace Maintenance Checklist (Step-by-Step Guide)
- Why Fall Is the Best Time for Furnace Tune-Ups
- 10 Ways to Make Your Furnace Last Longer
- Winter Heating Tips for Homes in the Bay Area
- How Often Should Air Filters Be Replaced? A Complete Guide
- HVAC Filters: What Bay Area Homeowners Should Know
- Why Changing Your Air Filter Prevents Breakdowns
- Fall HVAC Maintenance in Dublin
- Heating and Cooling Tips for Cupertino Homes
- Fall & Winter HVAC & Refrigeration Services
Comfort, ducts and indoor air
Cold rooms, drafts, dry air, humidity and what the ducts are doing.
- Cold rooms and uneven heating
- Winter indoor air and humidity
- Fix HVAC Ductwork Issues
- How to Find Duct Leaks in Bay Area Homes | Simple Tests
- Why Duct Sealing Improves HVAC Efficiency & Comfort
- How Does HVAC Zoning Work and Is It Worth It?
- Attic Insulation & HVAC Efficiency
- How Humidity Affects HVAC Performance
- Indoor Air Quality Guide for Bay Area Homes
- 10 Ways to Improve Indoor Air Quality
Heating bills and efficiency
Why winter bills jump and what actually brings them down.
- Lower winter heating bills
- Winter Heating Efficiency Tips for Your Home
- How to Lower Your PG&E Bill Using Smart HVAC Strategies
- Why Your PG&E Bill Suddenly Increased
- Why Your Energy Bills Are Spiking | HVAC Issues to Check
- Signs Your HVAC System Is Wasting Energy
Repair, replace or go electric
Costs, the repair-or-replace decision, and the Bay Area's rules on new gas furnaces.
- Gas furnace rules and heat pumps
- Furnace Repair or Replacement?
- Bay Area Furnace Repair Costs Guide
- Furnace Repair vs Replacement Cost in San Jose
- When to Replace Your Furnace in Los Gatos
- HVAC Repair vs Replacement: The 50% Rule
- Gas Furnace vs Electric Heating in California (2026)
- Heat Pump Installation Cost in California (2026)
- HVAC Replacement Cost in the Bay Area
- 6 Best Furnace Installation Companies in the Bay Area
Rebates and tax credits
What is still available in 2026, and what has ended.
- HVAC Rebates in California (2026): What Is Open, What Ended
- How Bay Area Heat Pump Rebates Work in 2026
- TECH Clean California Heat Pump Incentives: 2026 Status
- Federal HVAC Tax Credits in 2026: What Changed
Renters and landlords
What California law requires, and how to get a broken heater fixed.
Businesses
Rooftop units, restaurants, offices and commercial refrigeration in the cold months.
- Commercial heating in winter
- Commercial HVAC Maintenance Programs
- Commercial HVAC Repair | Bay Area Experts
- Rooftop HVAC Systems for Bay Area Buildings
- Energy Efficiency Tips for Commercial Rooftop HVAC Units
- Common HVAC Problems in Restaurants
- Emergency Commercial Refrigeration Repair
Heating help by city
Our city pages cover local permits, utilities and the housing stock we see in each area.
- San Jose
- San Jose furnace repair
- Santa Clara
- Sunnyvale
- Cupertino
- Campbell
- Los Gatos
- Milpitas
- Mountain View
- Los Altos
- Palo Alto
- Redwood City
- Woodside
- Fremont
- Newark
- Hayward
- Dublin
- Pleasanton
- Livermore
- Walnut Creek
- Morgan Hill
- Gilroy
- All service areas
When you would rather have a technician look at it
Cool Aid's technicians are California C-20 licensed and EPA Universal certified, and every job is covered by our 1-year parts and labor warranty. We repair, maintain and replace gas furnaces, heat pumps, ductless mini-splits, thermostats and ductwork, and we work on older wall and floor furnaces. For businesses we service rooftop units and commercial refrigeration.
Planning ahead? Our fall and winter services page lists the heating-season work we book. No heat right now? Call our 24/7 line at 1-800-266-5243.
Frequently asked questions
What should I check first when my heat stops working?
The thermostat (set to Heat, a few degrees above room temperature, fresh batteries), the breaker and the switch near the furnace, the furnace door, and the filter. Our no-heat checklist walks through each one in order and tells you where to stop.
Is it normal for a furnace to smell when I first turn it on?
A dusty, slightly burnt smell for the first few minutes to an hour or two of the season is dust burning off the heat exchanger. A smell that lasts longer, smells electrical or like rotten eggs is not normal. For rotten eggs, leave the house and call 9-1-1 and PG&E.
Do I need a carbon monoxide alarm?
In California, homes with a gas appliance, a fireplace or an attached garage must have carbon monoxide alarms (Health and Safety Code 17926). Put one outside every sleeping area and on every level. More in our gas and CO safety guide.
Why is my heat pump steaming or blowing cooler air than my old furnace?
Steam from the outdoor unit on a cold, damp morning is the normal defrost cycle. Heat pump air also comes out cooler than furnace air while still heating the house. Heat pumps in winter explains what is normal and what is not.
How often should I change my furnace filter in winter?
ENERGY STAR says to check it every month during heavy use and change it at least every three months (ENERGY STAR). Homes with pets, construction dust or wildfire smoke usually need more frequent changes.
Can I still buy a gas furnace in the Bay Area?
Yes. The Air District's zero-NOx rule for furnaces applies to new units sold or installed from 2029, and nobody has to remove a working furnace. Details and options are in Bay Area gas furnace rules and heat pumps.
My landlord has not fixed the heat. What can I do?
California law requires rental housing to have heating in good working order. Put the request in writing and keep a copy. Renters' heating rights covers timelines, local code enforcement and what the law does and does not allow.
What humidity should I keep my home at in winter?
The EPA recommends 30 to 50 percent (EPA). Below that you get static and dry skin; above it, condensation and mold on cold windows. See winter indoor air.
Do you work on wall heaters, floor furnaces and radiant heat?
We work on wall heaters and floor furnaces. Original in-slab radiant systems are a specialty of their own, and we will tell you honestly if a problem is outside our scope. We can add ductless heat pumps to homes without ducts. See wall and floor furnaces and radiant heat in Eichler homes.
Last reviewed 24 September 2026. Rules, rebates and utility programs change; each guide links the official source so you can confirm current terms.
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