Guides

• Why the 20 BTU per Square Foot Rule Oversizes Most Air Conditioners — The square-foot chart oversizes central AC in 2,150 of 3,206 US cities. Why it happens, what it costs you, and where the chart falls short instead.
• Humid or Dry: How Summer Moisture Changes the AC Size You Need — Warm summer nights mean wet air, and wet air adds load the thermostat cannot see. How much moisture adds to AC size across US climates.
• Is My Contractor's AC Tonnage Right? How to Check a Quote — Three questions to ask before you sign an AC quote, the Manual J and Manual S checks behind them, and the tonnage US cities actually need.
• Window AC and Mini-Split BTU by Room, Adjusted for Climate — Room AC charts assume one climate. Climate-adjusted BTU per square foot runs from 7.9 to 30.4 across US cities. Bedroom, living room and open-plan sizes.
• What Central AC Costs to Run, State by State — Median yearly cost to cool a 2,000 sq ft house in each state, from NOAA cooling degree days and EIA electricity rates.
• Embed the AC Size Widget for Any US City — A free live badge with the climate-based AC size, load and running cost for any of 3,206 US cities. One iframe, no sign-up.