If it seems like there are exit signs everywhere, it’s because there are an estimated 100 million exit signs in the United States consuming between 30 and 35 billion kWh of energy each year. Most use incandescent bulbs, which use large amounts of energy and require frequent maintenance.
The typical exit sign with incandescent bulbs uses two 20 watt bulbs. The signs are lit 24 hours a day and 365 days a year.
Let’s do the math for a single sign.
2 × 20 watts = 40 watts × 24 hours = 960 watt hours
960 × 365 days per year = 350,400 watt hours
Electricity is billed by the amount of kilowatt hours (kWh) used and the national average cost is $0.08 per kWh (adjust this cost for your schoo).
To convert watt hours to kilowatt hours (kWh), divide watt hours by 1,000.
350,400 watt hours divided by 1,000 = 350.4kWh × $0.08 per kWh = $28.03
Now let’s look at the other costs.
The incandescent bulbs cost approximately $3.00 each and the sign has 2 bulbs.
2 × $3 = $6
The bulbs have to be replaced an average of 3 times each year.
3 × $6 = $18
The bulbs don’t replace themselves so we have to add the labor cost.
Figure 1/2 hour per change or $10 labor per change × 3 = $30
Our annual total cost now includes:
Electricity costs = $28.03
Bulb cost = $18
Labor = $30
Total = $76.03 per year for 1 sign
How many signs are in your school? In your district? Is there a more efficient alternative to signs lit with incandescent bulbs?
If an LED exit sign that uses 2 watts costs $20 to purchase, how long until the energy savings pay for the cost of replacing the sign? Don’t forget to include the cost of the labor to replace the signs. Remember that the LED will last many years.
Prepare a report to be submitted to the principal, your energy manager, other administrators, or the school board.