I keep my house set at 78 in the summer, and my cabinet is set at 75 year round. The cabinet cooling runs off and on during the summer, but I don't think it costs more than a few pennies a day to operate it.
The distilled water usage for the humidifier increases considerably when the cooling kicks in. I have to remember to check the water level weekly during the summer, after pretty much ignoring it all winter.
All worth it to have happy cigars.
