This humidifier has a 4 gal capacity and will run 40 hours on a single filling. We purchased this humidifier for our bedroom but found it too large for that area.  It will humidify a large room up to 900 sq. ft.  We purchased a standalone unit for our living area and just leave the bedroom door open which works out fine.  I just installed a new filter at a cost of $13.00.  Here is an ad from Amazon:

Holmes Cool Mist Comfort Humidifier with Digital Control Panel, 
by Holmes

Amazon's Choice for "Holmes humidifier"
Price: $64.99 Free Shipping for Prime Members
The 16 hour programmable timer automatically turns the humidifier on and off
The Filter Check filter monitor indicates when a replacement filter is needed
The large tank is easy to fill and carry and runs up to 40 hours

I will sell the humidifier for $30.00.  Richard Fields 219 11th Ave W. Reply to email or call at (218) 387-1334

219 11th Ave W, Unit 118