A typical household LED is about 8–12 watts. That is why the old warning — “stop flipping the switch, you will run up the bill” — does not fit modern bulbs. The expensive part is hours the light is on, not how many times you click it.
Incandescent bulbs were 60 watts for a similar amount of light. Those are a different card in Whatt if you still have them. CFLs sit in the middle. An LED left on in a closet for a week is still a small number; a dozen cans on all evening is hours × 10 watts × 12 bulbs.
Startup does not “use a burst equal to hours of light.” Treat each hour of on-time as 8–12 watts and ignore the click.
Set watts per bulb and hours. For a whole fixture with several lamps, use the fixture card or multiply.
At 18.8¢ per kWh, one 10-watt LED for 5 hours is 0.05 kWh — about 0.01. Ten of those fixtures all evening is about 0.09. The AC in the next room is still the larger story.
The old warning
“Stop flipping the switch” was aimed at incandescent inrush stories. An LED’s expensive part is leaving the room lit. A dozen cans all evening is still hours × about 10 watts × 12, not a strobe penalty.
Related
Usage estimate only — not a utility bill, load calc, or advice.