1. Are they Cost-Effective? Brad Pittler & Patrick Sims
Energy Saving Devices
Are they Cost-Effective?
Brad Pittler & Patrick Sims

2. The Customer Southern Methodist University Michael Vangelli
University with roughly 10,000 students
Michael Vangelli
Campus Planning and Plant Operations
Electrical Engineer

3. Issues to be Resolved
Collect data regarding study room, rest room, and copy room usage.
Gather information regarding energy efficient devices
Compare installation costs of energy saving devices to what they would save over a period of time

4. Method of Data Collection
Automatic
Using “Intellitimer” Device
Using Circulation records from libraries
Using sign-out sheets
Manual
Counting people entering and exiting rooms
Using anecdotal evidence when available

5. Data Analysis Objective
To gather sufficient data to:
Develop a mean for each type of room
Develop a picture for room usage over a period of time
Develop a representative basis for recommendation

6. Problem Development
Data collected formed a cost/benefit problem (with the following assumptions):
The data collected was representative of the norm
The costs would be static, and labor would be ignored
Inconvenience of installation had no cost

7. Model Development
Goals were to calculate energy-cost savings for two different types of energy saving devices.
Calculating the time until the device pays for itself in energy savings
Implemented into the model three factors:
Data Gathered on Occupancy
Cost of Energy per kWh
Average Energy used per room (in kWh.)

8. The Model Annual Savings Model
(Percent of time unoccupied) X (Cost of energy) X (Energy used per room) X (16 hours) X (350 days)
This will calculate total energy savings.

9. The Model (Cont.) The Payback Period T = Unit Cost / Annual Savings
This will calculate how long the unit will take to “pay for itself” via energy savings.

10. Choosing the Devices
Gather information on options used for energy savings
Contact other organizations to learn about their choices
Learn about drawbacks and costs to install the devices

11. The Contenders
Leviton develops devices that use both IR and Ultrasonic to detect occupancy
WattStopper offers devices using either IR or Ultrasonic to detect occupancy

12. Drawbacks and Positives
Criteria
Leviton
WattStopper
Cost X
Ease of Procurement
Ease of Installation

13. Based on pattern (~16 minutes)
The Contenders (Cont.)
Device
Install Time
Unoccupied time
Cost (List Price)
Leviton Model 1000WAH
60 minutes
Based on pattern (~16 minutes)
$113.80
WattStopper WT-605 (for restrooms)
16 minutes
$134.00
WattStopper WA (for copy rooms)
30 minutes
18 minutes
$72.00
WattStopper WPIR
15 minutes
$102.00

14. Numerical Findings Cost of Solution Energy Savings
Time to Payback (years)
Study Rooms
$134 (WS)
$ (Lev)
$75.42
1.35 (WS)
1.51 (Lev)
Restrooms
$102 (WS)
$49.67
2.7 (WS)
2.29 (Lev)
Copy Rooms
$72 (WS)
$59.59
1.21 (WS)
1.91 (Lev)

15. Conclusions
In two of the three cases, installation of either device would have a payback period of less than two years.
Both devices had positive and negative points.
The decision would be made on choice between cost and convenience.
Further study of room usage patterns could contribute to better choices.