What it costs to run your lights

This is the other multiplication this site is built on, alongside the lumen arithmetic in how many lumens does a room need. It is just as short and almost nobody publishes it either.

Cost = (watts / 1,000) x hours x your rate per kWh.

Two notes on the inputs. Watts means actual draw, not the incandescent equivalence on the front of the box - an 8-watt LED sold as a "60W equivalent" consumes 8 watts. And use your own rate, printed on your electricity bill in cents per kilowatt-hour.

Every dollar figure on this page uses an illustrative rate of $0.17/kWh, chosen as a round mid-range number to make the arithmetic followable. It is not a claim about the current national average, and US residential rates vary widely by state - so the kWh column in the table below is the part to rely on, and the dollar column is the part to recalculate with your own number.

The last two rows are the ones worth sitting with. A whole living room lit properly by four LED sources costs less to run for a year than a single incandescent bulb producing 800 lumens did.

That is the practical conclusion of this entire page: with LEDs, running cost is no longer a reason to under-light a room. If your room is below the published lumen target, the electricity cost of fixing it is a few dollars a year. The reason to dim a light is comfort, not economy.

Every figure above comes from a published wattage and a stated rate, so you can redo it. But you can also measure it directly, which is better.

A smart plug with energy monitoring - the Kasa EP25 or the Tapo P115 - reports actual consumption for whatever is plugged into it. Budget models measure within a few percent of true consumption, which is far more precision than this question needs.

Put one on a torchiere for a week and you will have a real number for your own usage pattern rather than our assumed five hours a day. That is the kind of verification we would rather you did than take our word for - it is the whole basis of how we pick.