I recently stayed in an apartment that didnt have central air so I created a corsi-rosenthal box since the smoke from the Canadian wildfires were so bad.
After 30 days of continuous use, with very minimal periods of it being turned off, this is what the filters look like!
It's disgusting yet also so satisfying to see the filters get darker from debris, dust, and dirt.
Edit: typos
I looked up a 20 inch box fan on Amazon and it was rated for 67 watts. I ran it almost 24 hrs a day(kids loved to mess with it) and didn't notice it on my bill.
67 watts is 1.608 kilowatt hours per day. In California (one of the more expensive states for electricity), electricity costs $0.31/kwh. That would come to just under $0.50/day or $15/month.
Watts per hour isn't a thing. Watts is already a measurement of rate. 67 watts, running for 24 hours, is 1.608 kilowatt-hours.
The rest of your math checks out, assuming no hidden "distribution" or "transmission" fees (like I have).
Thanks for the clarification. Fixed.