Part 1 - LED Lighting's Impact to Our Home

The Energy Independence and Security Act of 2007, signed by President George Bush on December 18, 2007 was an energy policy intended to make better use of our resources and help the United States become energy independent.  Part of the law sets energy efficiency standards for light bulbs; the first phase went into effect January 2012. The incandescent light bulbs were phased out January 1, 2012 for 100 watts, January 1, 2013 for 75 watts and January 1, 2014 for 60 and 40 watts.  The following table shows the incandescent wattage and its equivalent lumen and LED-CFL wattages (Source: www.energystar.gov/la/products/lighting/cfls).

Incandescent Bulb (Watts)	Minimum Light Output (Lumens)	Common Energy Star Qualified Bulbs (Watts)
25	250	4 to 9
40	450	9 to 13
60	800	13 to 15
75	1100	18 to 25
100	1600	23 to 30
125	2000	22 to 40
150	2600	40 to 50

Efficiency is measured by the number of lumens per watt.  Brightness is measured by the number of lumens.  Watts is the amount of energy that a light bulb uses.

  

Below is a comparison of incandescent, CFL and LED bulbs

• A standard 60 watt incandescent light bulb provides 13 to 14 lumens per watt.
• An equivalent CFL provides between 55 and 70 lumens per watt.
• An equivalent LED provides between 60 and 100 lumens per watt.

Source: www.energystar.gov/la/products/lighting/cfls

My first foray into efficient lighting was CFL.  I purchased about a dozen of them and placed them in the bathrooms and entertainment room.  They worked fine in the bathrooms, but flickered in the entertainment room.  The lights were also a bit antiseptic, not the soft white of the incandescent bulb.  My second foray was purchasing two, first- or second-generation light bulbs and they were terrible – blue and ugly.  So, I waited another year.  Then, Xcel Energy and Cree offered 40-watt LED bulbs for $4.99.  I purchased 20 LED bulbs in August 2014.  Being an energy analyst, I set up a spreadsheet to measure the electricity use of my house over the past 17 months and included Xcel’s electricity usage by my neighbors and my most energy efficient neighbors.

I have included three graphs that I have generated from my electricity bills and Xcel Energy’s web based data tools.  The first graph illustrates my family’s (2 adults, 2 teenage sons) electrical usage.  As you can see the electricity spiked in August 2014 and then dropped off appreciably.

The second graph shows the above kWh used and is overlain with temperature data (provided by Xcel Energy).  You can see from the chart, that electricity usage is highly correlated to temperature in May, June, July, August, September, and October.  Then it switches to an inverse correlation during November, December, January, February, March and April.  During the summer months, the air conditioner kicks in during hot days.  We agreed to have an energy saver device installed to our A/C system.  When there is peak load demand during the hot days, the energy saver device is activated and reduces the flow of electricity into our home and allowing the A/C to shut off for longer time periods.  We receive a price discount for that energy savings.  During the winter, you can see energy usage peak, when temperatures are at their lowest.  The increase in energy usage is due to the furnace blower heating the house. 

 

More interesting is the sharp drop of electricity usage from August to September 2014.  The temperature dropped from an average of 70 degrees F for the period of July 17 to August 17 to an average of 65 degrees F for the period of August 17 to September 15.  The corresponding electrical usage dropped from 1721 kWh to 947 kWh.  Clearly some of that drop was due to reduced summer temperatures and some of that came in the form of the highly efficient LED bulbs. 

To see the contribution of LED lighting, it is better to compare the winter usage January 2014 to January 2015.  From December 16 to January 19, 2014, the average temperature was 12 degrees F and electricity usage was 1557 kWh.  For the corresponding period in 2015, the average temperature was 16 degrees F and electricity usage was 1253 kWh.  That is a drop in electricity usage of 19.5%.

During the month of August, when I installed the LED bulbs, my comparison to my neighbors and my energy efficient neighbors, our energy usage dropped below our average neighbors’ usage and just above the most energy efficient neighbors.  I then checked into Xcel’s database to see who I was being compared to - homes that were smaller and homes that were newer and therefore more energy efficient. 

Since August 2014, we have stayed within the band of the most energy efficient neighbors and the average neighbors electricity band.  That demonstrates that the LED bulbs have been a reasonable contribution to energy savings.