I live in Canada. Every BTU an incandescent lightbulb gives off in times when you use space heaters in your living spaces is a BTU not spent by your space heaters, in other words: The heat given off by incandescent lightbulbs is heat that is saved, not spent, by space heaters, meaning incandescent lightbulbs are 100% efficient in the winter.

I live in Canada. Every BTU an incandescent lightbulb gives off in times when you use space heaters in your living spaces is a BTU no spent by your space heaters, in other words: The heat given off by incandescent lightbulbs is heat that is saved, not spent, by space heaters, meaning incandescent lightbulbs are 100% efficient in the winter.