Sizing Guides

Longer reads for when the number alone is not enough. Each guide is written to answer the question in the title without padding, and every figure matches what the calculator produces.

• What Size AC Do I Need? A Plain-English Sizing Guide

  How to pick the right BTU for a window, portable, or mini-split AC: the 20 BTU per sq ft rule, what changes it, and why the next size up is usually wrong.

  8 min read. Reviewed September 2026.

• Mini-Split Sizing Guide: BTU per Zone, Multi-Zone Math, and Mistakes

  Size a ductless mini-split properly: per-room BTU, why inverter units tolerate slight oversizing, multi-zone traps, and cold-climate heating.

  9 min read. Reviewed September 2026.

• Why an Oversized Air Conditioner Is Worse Than a Small One

  Short-cycling, sticky humidity, higher bills and a compressor that dies early: what happens when an AC is too big, and how much bigger is too big.

  7 min read. Reviewed September 2026.

• Space Heater Sizing: How Many Watts (and BTU) Your Room Needs

  Match a space heater to your room: the 10 watts per sq ft rule, when 1,500 W is enough, when you need 240 V, and how insulation and climate shift it.

  7 min read. Reviewed September 2026.

• Window vs. Portable AC: Why the Same BTU Cools Differently

  Portable ACs lose a third of their rated cooling to the exhaust hose. How SACC ratings work, how to compare units honestly, and which type fits your room.

  7 min read. Reviewed September 2026.

• How Insulation Changes Your BTU Needs (With Real Numbers)

  Poor, average and good insulation can swing a room's heating load by 40%. How to judge your walls, windows and attic, and what it does to the BTU math.

  8 min read. Reviewed September 2026.

• What Size AC for a Garage? BTU for 1, 2 and 3-Car Garages

  An uninsulated 2-car garage needs a 14,000 to 24,000 BTU AC. Real numbers for 1, 2 and 3-car garages, mild vs hot climates, and which unit type works.

  7 min read. Reviewed October 2026.