Furnace Buying Guide: Gas vs Electric for California

AFUE (Annual Fuel Utilization Efficiency) measures how much of the gas a furnace converts to heat vs waste. An 80% AFUE furnace converts 80 cents of every dollar of gas into heat; 20 cents goes up the flue.

• 80% AFUE: Standard efficiency. Uses a chimney/flue vent. Most affordable.
• 90–96% AFUE: High efficiency. Condensing technology. PVC vent pipe (no chimney needed). Significantly lower gas bills.
• 97–98% AFUE: Ultra-high efficiency. Variable-speed blower. Quietest and most even heating.

• Single-stage: On or off. Simplest. Loudest. Most affordable. Good for mild climates like LA where heating demand is low.
• Two-stage: Runs at low capacity most of the time, high only when needed. Quieter, more even temperatures. 5–10% more efficient.
• Variable-speed: Adjusts output continuously from 40–100%. Whisper-quiet. Most even temperatures. Best air filtration (fan runs longer at low speed). 15–20% more efficient than single-stage.

California is pushing toward building electrification, with many cities banning gas in new construction. However, for existing homes with gas infrastructure:

• Gas furnace: Lower operating cost per BTU in most of CA. Heats faster. Works during power outages (with battery backup).
• Electric furnace: No combustion, no CO risk. But very expensive to operate — essentially a giant space heater.
• Heat pump (recommended): 2–3x more efficient than electric resistance heating. Qualifies for tax credits. The best electric alternative to gas.