So my Nitecore d2 draws .25 amps. Running it for an hour cost $ .00529 per hour.
A 40 watt bulb costs $.004 - $ .006 per hour.
A 40 watt bulb puts out 400-450 lumen.
Takes the d2 about two hours to charge an 18650. A flashlight running at 400 lumens is going to deplete the battery in two to four hours.
I guess what I am asking is per lumen it seems cheaper to use house current lights vs. a flashlight when you figure in the initial cost of the battery, charger ect
Is there a Newtons law where input equals output? Or am I missing something?
Compare (best you can) lm/watts, then factor in price of cell(s) and charger, charging cable, adapter etc.
Include price of the lightbulb, if you wanted to really go nuts.
I guess it’s up to you whether you include cost of the flashlight or not.
Figure charger is 90% efficient so include this in your calcs too.
Likely cheaper to run the household lights, all things considered, given you’re using the electric directly rather than mains> charger > cell > flashlight.
A better calculation is whether expensive LED bulbs with higher efficiency are cheaper in the long run than cheap, lower efficiency LED bulbs…
Yeah, a light bulb seems to be 1 watt = approximately 10 lumens. So cost per watt is .0004/.0006. cost $1.30 for 10,000 - 25,000 hours.
Flashlight that can hold 400 lumens running on 18650 is probably between 30-40$ and battery is 5-6$. Runtime is iffy. Flashlight should last 6-10 years and battery maybe 300-800 charges .
Each have their place and convenience wise the flashlight wins hands down.
All this was about is how close the (energy in cost) is almost the same in both scenarios.
I guess you get what you pay for. My prediction was my 400 lumen from a flashlight was much cheaper than the 400 lumen house current.