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
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
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
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
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
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