Are Infrared Lights Expensive to run?

Well, that depends on the rate you pay for electricity. You say that it turns on and off, let's say that it's on half the time and off half the time, that means that in a day it's on for about 12 hours out of a 24 hour day therefore in a 30 day month, it's on for 360 hours. It's a 75 watt bulb, multiply 75 by 360 and you have 27,000 W hours. Electricity is charged by the kilowatt hour so divide 27,000 W hours by 1,000 to get 27 kWh. In the North America, electricity costs from 7 cents per kWh to 25 cents per kWh so that would be from $1.89 a month to $6.75 a month. I've seen someone from the UK post that they pay 19p per kWh which would be a God awful, riot in the streets, burn down all government buildings rate in North America, but at that horrendous rate you would be paying £5.13 per month.