The overwhelming majority of lights in residential
households are incandescent--the least energy efficient of all
light types (Figure ES1.). If households replaced the most intensively
used bulbs with compact fluorescent bulbs, they would see a sizable
savings in their electric bills. The total U.S. household energy
that would be saved by replacing all incandescent bulbs used 4
or more hours per day would be 31.7 billion kilowatthours (kWh)
annually, or 35 percent of all electricity used for residential
lighting.
The amount of time it takes for households to see
a simple payback from compact fluorescent bulbs depends on the
price of electricity. Assuming a 26-watt compact fluorescent bulb
that costs 22 dollars, an average sized 75-watt incandescent bulb
that costs 75 cents, and that the lights are used 6.7 [1]
hours per day, households see a savings in 2.5 years,
if the electric rates are five cents per kilowatthour (Figure
ES2). Households see a savings in 1.1 years if the rate is 15
cents per kilowatthour. At the national level, the average cost
of electricity is 8.4 [2]
cents per kilowatthour. At this rate, compact fluorescent
bulbs pay for themselves in 1.7 years.
The life-cycle cost of a light bulb includes the
cost of the bulb itself, as well as the cost of the electricity
required to power the bulb. Electricity costs are a large percent
of the life-cycle cost of incandescent lights. Depending on the
electric rates, electricity costs account for 78 to 91 percent
of the life-cycle cost of incandescent lights, but only 37 to
63 percent of the life-cycle cost of compact fluorescent bulbs
(Figure ES3).
Compact fluorescent bulbs need about one-third of the power required by incandescent bulbs to emit the same amount of light. [3] If one wanted to replace a 75-watt incandescent bulb, a 26-watt compact fluorescent would be an appropriate choice. Therefore, regardless of electricity costs, compact fluorescent bulbs offer a three-fold increase in efficiency. If compact fluorescent bulbs, by virtue of their high cost, do not produce large dollar savings to individual households, they still result in large savings of electricity and the fuels required to produce electricity.
According to the 1993 Residential Energy Consumption
Survey, U.S. households have, on average, 5.4 indoor lights that
are on one or more hours per day, and 8.9 lights that are on 15
minutes or more per day. [4] They
use 940 kWh of electricity for lighting each year, and spend 83
dollars on electricity for lighting. Their expenditures on electricity
for lighting are about 10 percent of their total electric bill.
Nearly every household uses lights and all households
with lights use electricity to power them. However, electricity
consumption for lighting is only 9.4 percent of all electricity
consumption in the residential sector. Space heating, water heating,
air conditioning and other appliances each accounts for more electricity
use than lighting (Figure ES4).
The bedroom is the room that contains the most household
lights. However, the lights in the living room and kitchen are
used the greatest number of hours (Figure ES5). Although 27 percent
of all lights are in bedrooms, they use only 19 percent of the
total light-hours. [5] On the other
hand, the living room has only 17 percent of all lights, but accounts
for 22 percent of all light-hours. One reason bedrooms have the
highest number of lights is that the average home has 2.6 bedrooms.
The cost of electricity varies by Census region,
from 7.7 cents per kilowatthour in the South to 11.4 cents per
kilowatthour in the Northeast. The Midwest and West have similar
rates--8.1 and 8.3 cents respectively. As the cost of electricity
increases, households use less of it for lighting. However, with
increasing electricity prices, the amount of electricity used
for lighting accounts for a greater percentage of the total electric
bill (Figures ES6 and ES7). This occurs because when electricity
prices are higher, households choose fuels other than electricity
for the more intensive uses, such as space heating, water heating,
and cooking.
The 1993 Residential Energy Consumption Survey collected
information about lighting from two sources--the Household Questionnaire,
answered by 7,111 households, and a Lighting Supplement, administered
to a subset of 474 households.
General descriptions of the basic types of lights discussed in this report are presented in Figure ES8.
