Skip to main content
Help Center Community Shop

for electricians - or just smart people

slipgate
Leaving a light on when not needed wastes energy, but how much more energy is wasted by leaving a 100 watt bulb on when no one needs it as far as the air conditioning system is concerned? So in other words, how much heat is added to the room that must be removed by the air conditioner?
0

Comments

13 comments

Date Votes
  • Colt Super
    Too many variables.

    Incandescent bulb ??

    Total room volume ??

    Ambient air temperature ??

    Time of day ??

    Probably more.

    Doug
    0
  • longsantafe
    1 btu= 1kws [kilo watt second] -/+
    1 btu= 1 degree f/ lbs water

    a 100 [.1kw]watt bulb x 1 hour = 360 btu

    360 btu will change the temerature of 6 cases of beer from 100 degrees to 40 degrees f

    now would you rather drink warm beer or drink in the dark.
    0
  • Marc1301
    Also a 100 watt bulb gives off roughly the same quantity in BTU's of heat per hour, as an average resting human does within the space.
    There are 12,000 btu's to a ton of A/C capacity.
    Therefore the bulb requires .03 of a ton per hour of cooling to displace it.
    0
  • Colt Super
    That valid stuff doesn't apply unless you answer the questions I asked to begin with.

    Doug
    0
  • Marc1301
    quote:So in other words, how much heat is added to the room that must be removed by the air conditioner?
    Assuming incandescent, the btu per hour is valid, and the percentage of a ton of a/c required are also correct.
    No other variables apply to HIS question above!
    360 BTU's per hour / .03 ton
    The room size, and things like outdoor ambient have no effect on what a 100 watt bulb puts off in terms of heat in an hour. That is a constant.
    The only factor that will change the heat output of a given load, is variations in incoming voltage which are very minor.
    Now if he was asking how long it would take to remove that heat, some of the variables would certainly apply.
    0
  • Colt Super
    You are right, Mark.

    I was trying to place the question into a meaningful, real-world, format.

    Doug
    0
  • Marc1301
    And on that point Doug,.......YOU are correct![;)]
    Same reason our electric bill rises the hotter it gets outside!
    0
  • tsavo303
    no doug, not all you questions matter
    100 sq ft or 1000 heat generated is the same
    incandesent is about 1/3 or regular
    0
  • longsantafe
    100 watts
    if your air conditioer is %50 efficiant it takes 200 watts of air conditioner to break even.
    0
  • longsantafe
    so you are loosing 300 watts for nothing.
    0
  • Colt Super
    Me poor little head now hurts.

    Doug
    0
  • jthoresen
    Let's say a 100W light bulb costs $4 to run for 24 hours. A typical central air condition system is four times as efficient removing BTU's as the light bulb is at adding BTU's. (Assume that this is roughly a 10000 BTU unit using 600 watts). This should cost you $5.00 at 24 hours.
    0
  • slipgate
    So it costs @$9 to run a 100 watt bulb for 24 hours?

    nevermind - i see your logic, $4.00 + $1.00 so $5.00 for 24 hours.
    0

Please sign in to leave a comment.

Recent Activity