HVAC questions, answered
Short, sourced answers. Each one links to the tool that answers it for your home.
Costs
How much does it cost to repair an AC?
$150–$650 for most repairs, $360 on average. Price your part →
How much does a furnace repair cost?
$125–$480, $300 on average.
How much does an HVAC service call cost?
$75–$200.
How much does a new furnace cost?
$3,000–$10,000 installed for a gas furnace; $2,500–$7,000 for electric. Estimate yours →
How much does it cost to replace a central AC?
$5,000–$9,500 installed depending on size (1.5–5 tons) at standard efficiency.
Repair or replace
What is the $5,000 rule?
Age × repair cost. Over 5,000 → replacing usually makes more sense. Run it →
How long does an AC last?
15–20 years. Heat pumps 10–20; gas furnaces 15–25; electric furnaces 20–30.
Sizing
How many BTU do I need?
About 20 BTU per square foot of room, adjusted for sun, people and kitchens. Calculate →
How many BTU is a ton?
12,000 BTU per hour = 1 ton = 3.517 kW.
What size AC for a 2,000 sq ft house?
Usually 3.5–4.5 tons. See the chart →
What size mini-split do I need?
Size each room separately at ~20 BTU/sq ft and round up to the next head size. Size it →
Troubleshooting
Why is my AC running but not cooling?
Clogged filter, thermostat fan on ON, dirty outdoor coil, failed capacitor, or low refrigerant. Diagnose →
Why is my furnace blowing cold air?
Fan set to ON, an overheating furnace from a clogged filter, or a dirty flame sensor.
Where is the AC reset button?
Many outdoor units have a small red reset button near the bottom of the cabinet or behind the service panel; many do not have one at all. Resetting the breaker does the same job.
Estimates for planning only. Prices vary by region, home, and contractor. Gas, refrigerant, and high-voltage work must be done by a licensed technician.