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Hot shower = 4000 LED bulbs


How much energy does it take to run a shower?

Enough to power about 2000 LED light bulbs! That's 20kw, almost as much as the total electrical power to many homes.smiley bulb.jpeg

How much could I save by switching to a low-flow shower head?

40% - enough to power about 800 light bulbs!

How about short showers?

Yes! The quicker the shower, the less energy used!

Bathtub?

Bathtub sizes run from 40 to 100+ gallons; that's like running a shower 16 to 40+ minutes to fill, running 2000 light bulbs the whole time.

I'm cold!

Wear warmer clothes, cozy up in a blanket, or turn up the heat - you'll still save energy, compared to warming up in the shower. It takes a lot of energy to heat water, and it's a huge waste to run it off your body and straight down the drain.

Save more, greater comfort

Enclosing your shower can cut drafts and make your shower more comfortable, even with less energy, and you can comfortably turn off the water while soaping. This site shows one way: http://www.instructables.com/id/Cozy-Low-Energy-Shower. I take a simpler approach - I hang a cut-off shower curtain above the door to my shower.

Calculations

The calculations are based on:
  • 2.5 gallons/minute for a normal shower,
  • 3.8 liters/gallon
  • 4187 Joules to heat 1 liter of water 1 degree C
  • heat water from 50 to 104 degrees Fahrenheit (30 degrees C)
  • 1 Watt = 1 Joule/second = 60 Joules/minute

    water droplet.jpegHence, the wattage needed to continuously heat water for a normal shower is

  • 2.5 * 3.8 * 4187 * 30 / 60 = 19888.25 watts, almost 20 kilowatts

    20 kw corresponds to 2000 10-watt compact fluorescent light bulbs.

    That 20 kilowatts is nearly as much as the total electrical capacity of many homes. The typical standard for modern homes is 100 amp, 220 volt service (see this link), or 22 kilowatts.

    Installing a low-flow shower head (1.5 gpm) saves 40% of that, 7955 watts or about 800 bulbs, but it still uses 1200 bulbs worth. An older shower head may use over 5 gpm, over 4000 light bulbs.

    How many incandescent bulbs? Compact fluorescent?

  • 800 lumens = 60 watt incandescent, 14 watt CFL, or 10 watt LED.
  • That 20kw shower would power 333 incandescent or 1425 CFL bulbs.
  • Caveats

    At different times of the year, and in different parts of the country, the outside temperature is warmer so you don't need to heat the water 54 degrees. E.g. if the ambient water temperature is 77 degrees, then cut everything in half.

    This does not consider conversion losses (when producing electricity), transmission losses, efficiency of a gas or oil hot water heater, or the energy cost for delivering gas or oil to homes. It ignores evaporation - that steam from your shower comes with evaporative cooling, sucking heat out of the air in your home. Now if you're in a hot climate you may think that's good - but if you're running the air conditioner, it uses even more energy to reverse the process to get the moisture out of the air.

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