Overview
The core idea
Heat removal
AC moves heat out of your home — it never creates cold.
Refrigerant cycle
A chemical refrigerant continuously evaporates and condenses to carry heat.
Energy use
The compressor is the primary power draw — typically 1,200–5,000 watts.
Interactive diagram
How it works
Key components
The parts that make it work
Evaporator coil
The indoor coil where cold refrigerant absorbs heat from room air. Air blows across the coil, cools down, and returns to the room.
Compressor
The heart of the system — pressurizes refrigerant gas, raising its temperature dramatically. The main electricity consumer.
Condenser coil
The outdoor coil where hot, pressurized refrigerant releases its heat to the outside air. Fans accelerate heat dissipation.
Expansion valve
A precision valve that drops refrigerant pressure rapidly, causing it to cool before entering the evaporator.
Refrigerant
The working fluid — R-410A is most common. Cycles between liquid and gas states to transport heat.
Air handler
The indoor blower unit that circulates air across the evaporator coil and distributes conditioned air through ducts.
By the numbers
Efficiency comparison — SEER ratings
Tips & maintenance
- Set your thermostat to 78°F when home and 85°F when away — each degree lower increases energy use by 3%.
- Clean or replace your air filter every 1–3 months. A clogged filter forces the system to work harder and can freeze the evaporator coil.
- Keep the outdoor condenser unit clear of debris, plants, and direct sunlight. A shaded unit runs 10% more efficiently.
- Have refrigerant levels checked every 3–5 years. Low refrigerant is always a leak — the system is sealed and doesn't consume refrigerant.
- Install a programmable thermostat. A 7–10 degree setback for 8 hours daily saves up to 10% on annual cooling costs.
FAQ
Common questions
The most common causes are a dirty air filter restricting airflow, low refrigerant from a leak, a frozen evaporator coil, or a failed compressor. Check the filter first — it's the easiest fix and responsible for 30% of AC problems.
SEER (Seasonal Energy Efficiency Ratio) measures how much cooling an AC delivers per unit of electricity over a season. Higher SEER = lower energy bills. The minimum legal SEER in most US regions is 14; premium units reach 26+.
Once a year, ideally in spring before cooling season. A professional tune-up includes cleaning coils, checking refrigerant, lubricating moving parts, and testing electrical connections. Regular service extends equipment life by 5–7 years.
Either the unit is undersized for the space, there's a refrigerant leak reducing efficiency, the evaporator coil is dirty, or outside temperatures are extreme. A system that never cycles off is working harder than it should and wearing out faster.
Most systems installed after 2010 use R-410A. Older systems use R-22 (Freon), which was phased out in 2020 due to ozone depletion. R-22 is now expensive and scarce — if your old system needs a recharge, it may be more cost-effective to replace the unit.
Yes — as a byproduct of cooling. When warm, humid air passes over the cold evaporator coil, moisture condenses on the coil surface and drains away. A properly functioning AC typically removes 20–30 pints of moisture per day.