Frequently asked questions

You tell a calculator about your space or your power needs — room size, dampness, the appliances you want to run — and it computes the exact spec you need (CADR, BTU, watts, watt-hours, and so on). Then it shows you products that actually meet that spec, ranked by rating and value.

They use the same industry rules of thumb the pros use — AHAM for air purifiers, DOE for dehumidifiers, roughly 20 BTU per square foot for air conditioners, and so on. They’re excellent for choosing a product with confidence, but they’re estimates, not a substitute for a professional load calculation on a whole-home system or an unusual space. When in doubt, size up slightly.

Completely. Every calculator and guide is free, with no sign-up required. We make money through affiliate links, not from you.

We’re an Amazon Associate: when you buy through one of our links, we may earn a small commission at no extra cost to you. That funds the site and keeps everything free — and it never changes the number a calculator gives you or which products we rank first.

Prices change constantly, and the Amazon Associates rules require live prices to come from their API. Rather than show a stale number, we link you straight to Amazon, where you’ll always see the current price before you buy.

We start with the spec, not the commission. Products are filtered to those that actually meet your calculated requirement, then ranked by rating, review count, and how closely they fit — so you’re not paying for capacity you’ll never use.

No. The calculators run entirely in your browser, and the values you enter never leave your device or get saved on our servers.

The calculator will tell you when your need exceeds our current lineup — usually a sign to look at a larger unit, or to split the job across two (two air purifiers, two fans, more solar panels). Our buying guides explain when that’s the right call.