High speed uses more power, but not as much as you'd think

Box fans do use more electricity on high speed, but the difference is smaller than most people expect.

Here’s the deal: a typical 20-inch box fan on low might pull around 40–50 watts. On high, it’s more like 70–90 watts. So yes, high speed uses more power — roughly 50–80% more. But we’re talking about a difference of maybe 30–40 watts. At average US electricity rates, that works out to something like a penny or two per hour.

Running that fan 10 hours a day on high instead of low costs you maybe an extra $5–7 over an entire hot summer. It’s not nothing, but it’s also not where you’re going to see big savings on your electric bill. If you’re trying to cut power usage, you’re better off looking at air conditioning, appliances, and lights.

So run it on high if you want the breeze. The savings from low are barely worth thinking about.