I can only estimate how much money I spent with my old electric attic fan. This solar fan is supposed to install in 30 minutes, but it actually took about an hour. The fan was lighter than I expected but installation went smoothly. I purchased the optional thermostat and I am glad I did...it works extremely well. On the day of installation, the outside temperature reached 92 degrees. The attic temperature was well above 80 when the thermostat was plugged in completing the solar power circuit. The fan immediately began working to vent the attic.I did encounter one problem which most fan manufacturers could only wish they had. This fan is SO QUIET you cannot tell if it is operating from inside or outside the house. On the day after installation I actually checked in the attic to make sure it was working! EXCEPTIONALLY QUIET! I will get a better estimate of savings next year when the San Antonio heat does its worst. For now, I highly recommend this product for the overall build quality, ease of installation and silent operation.Update 11/3/2010: A few days after installation, our neighborhood in San Antonio experienced an extremely heavy hail and wind event. Hail was up to 3/4" diameter with wind gusts over 50mph. Yesterday afternoon we checked the fan and solar panel and all survived unscathed...not even a scratch on the solar panel. Fan with thermostat continues to work flawlessly. Outstanding product, superb build quality.