5th Grade Energy Efficiency

My 10 year old recently finished a science unit on energy efficiency in her 5th grade class.  Upon completion of the unit, students received an energy efficiency kit from the local power company.  In the kit were a couple of LED light bulbs, a low flow shower head, a low flow sink head, and an LED night light.  When we first moved into our house we slowly changed all incandescent light bulbs to energy efficient fluorescent light bulbs (those curly ones).  Recently we've started changing the fluorescent light bulbs, as they go out, with even higher efficiency LED bulbs. 

LED night light similar to the one my daughter brought home.

The LED night light my daughter brought home has a 1 Watt bulb in it.  This compares to the 4 Watt incandescent bulb in my daughter's current night light.  This means the LED light uses one fourth the energy of the incandescent light.  This is similar to the difference in a standard 60 Watt bulb and a standard LED replacement.  Most LED replacement bulbs are 9 Watts, meaning they use about 6.7 times less energy.  A greater energy savings than this night light, but similar.  The bigger question though, is how much money this one night light saves.  Let's take a look.

The difference in wattage is 3 Watts, which is an energy savings of 3 Joules per second.  The night light is probably on each night for approximately 10 hours.  There are 3600 seconds in each hour, so this is a total of 36,000 seconds.  Multiply by 3 to get the number of Joules saved per night.  This works out to 108,000 Joules.  Now consider 365 nights per year.  Multiply by 365 to get 39,420,000 Joules per year.  That may seem like a huge amount of energy, but a Joule is a tiny amount of energy.  Let's convert this to kW*hr as this is the common energy unit reported on your energy bill.  This gives us an energy savings of about 11 kW*hr.  An average energy cost per kW*hr is about 12 cents.  Thus this single LED night light will save us about $1.32 per year.

Okay, that's not much.  We are not suddenly doing a three month summer cruise around the world with this savings.  But it is a savings and once you factor in ALL light bulbs in your house, the savings can add up quickly and easily cover the extra cost of purchasing an LED light bulb versus an incandescent light bulb.  Yes, LEDs cost more initially, but they last much longer and use much less energy, resulting in much greater savings down the road.  Start slow by replacing bulbs one at a time as they go out in your house.  Replacing all bulbs at one time is a very daunting cost that not even I could swallow.  One light bulb at a time, however, is much easier to handle.