Leaving the porch light on all night started costing me $11 a month, so I switched to a timer
Honestly I always figured a single porch bulb was too small to matter on the power bill. Then my neighbor Dale, who used to work for the electric company here in Dayton, told me a 60 watt bulb left on 12 hours a night adds up to about $2.60 a month at our rates. I checked my last three bills and sure enough, the months my wife left it on nonstop ran $9 to $11 higher than the months she didn't. Bought a $14 plug in timer at the hardware store and set it for 6pm to 11pm. Has anyone else actually measured what one little bulb is costing them, or is it just me and Dale keeping tabs on this stuff?
That $2.60 a month math from Dale is pretty much spot on, a 60 watt bulb running 12 hours a day burns about 22 kWh a month, and at Ohio rates that's right in that range. I put a timer on mine two winters ago after my wife kept forgetting to shut it off, and the bill dropped enough that the timer paid for itself in about two months. If you want to shave a little more, swap that 60 watt for an LED, same light for like a buck a year.