ASHRAE Journal - May 2011 - 34

development of load factors discussed later, the diversity factor for notebooks was assumed to be the same as for desktop computers.

Factors for Office Equipment Device Desktop Computer LCD Monitor Notebook Computer Recommended Diversity Factor 75% 60% 75%

sumption. However, the new data suggests that the time has come to reexamine the use of 1 W/ft2 (10.8 W/m2) as the default industry norm.

Impact on Load Factors
The most useful form of this data for use by engineers performing load calculations is when it is presented as a load factor such as watts per square foot (W/ ft2). This new equipment and diversity factor data were coupled with some general assumptions and used to generate the updated load factor data presented in Table 3. It can be seen that if 100% notebook use is assumed and typical diversity factors are applied, plug loads could realistically be as low as 0.25 W/ft2 (2.7 W/m2). Even light and medium use of desktop computers results in plug loads below the traditional 1 W/ft2 (10.8 W/ m2). More extreme scenarios can be considered such as the case where all workstations use two full-sized monitors that can result in plug load of 1 W/ft2 or more. The most extreme scenario considered assumes very dense equipment use with no diversity at all and results in a plug load factor of 2 W/ft2 (21.5 W/m2). The load factors presented are based on hypothetical conditions with the best available data applied to them. Each of these includes a factor to account for some level of peripheral equipment such as speakers. This analysis suggests that there will be many cases where the design plug load can be assumed to be below the traditional value of 1 W/ft2 (10.8 W/m2) without risk of under-designing
Type of Use 100% Notebook – Light 100% Notebook – Medium 50% Notebook – Light 50% Notebook – Medium 100% Desktop – Light 100% Desktop – Medium 100% Desktop – 2 Monitors 100% Desktop – Heavy 100% Desktop – Full On
Load Factor (W/ft2)

References
1. Wilkins, C.K., R. Kosonen, T. Laine. 1991. “An analysis of office equipment load factors.” ASHRAE Journal 33(9):38 – 44. 2. Wilkins, C.K., N. McGaff in. 1994. “Measuring computer equipment loads in off ice buildings.” ASHRAE Journal 36(8):21 – 24. 3. Hosni, M.H., B.W. Jones, J.M. Sipes, H. Xu. 1996. “Test Method for Measuring the Heat Gain and Radiant/Convective Split From Equipment in Buildings.” ASHRAE Final Report for Research Project 822-RP. 4. Hosni, M.H., B.W. Jones, Y. Xu. 1999. “Measurement of Heat Gain and Radiant/ Convective Split From Equipment in Buildings.” ASHRAE Final Report for Research Project 1055-RP. 5. Wilkins, C.K., M.H. Hosni. 2000. “Heat gain from office equipment.” ASHRAE Journal 42(6):31 – 39. 6. Koomey, J., M. Cramer, M. Piette, J. Eto. 1995. “Efficiency Improvements in U.S. Office Equipment: Expected Policy Impacts and Uncertainties.” Lawrence Berkeley National Laboratory. 7. Hosni, M.H., B.T. Beck. 2010. “Update to Measurements of Office Equipment Heat Gain Data.” ASHRAE Final Report for Research Project 1482-RP. 8. Kawamota, K., et al. 2001. “Electricity Used by Office Equipment and Network Equipment in U.S.: Detailed Report and Appendices.” Lawrence Berkeley National Laboratory. 9. Moorefield, L., B. Frazer, P. Bendt. 2008. “Office Plug Load Field Monitoring Report.” Durango, Colo.: Ecos.

Table 2: Recommended diversity. the system. There are many factors that could impact the actual plug load for a specific space or building and careful consideration must be given to the assumptions used for any given condition.

Conclusions
Nearly all building projects today have a goal of using the minimum energy possible and having a small overall carbon footprint. Computer equipment used in offices has been a part of the overall trend toward energy use reduction. It is now possible to realistically conceive of an office space that could have a peak plug load as low as 0.25 W/ft2 (2.7 W/m2). When this lower plug load level is coupled with the lower lighting power density targets, the result is the building internal loads are being reduced to very low levels. Using a very low plug load assumption in an attempt to design ultra-low energy buildings comes with some risk. The occupant at the time of design may have fully embraced a low-energy office mentality, but in the future, there may be new occupants with less dedication or equipment with different energy con-

Description 167 ft2/Workstation, All Notebook Use, 1 Printer per 10, Speakers and Misc. 125 ft2/Workstation, All Notebook Use, 1 Printer per 10, Speakers and Misc. 167 ft2/Workstation, 50% Notebook/50% Desktop, 1 Printer per 10, Speakers and Misc. 125 ft2/Workstation, 50% Notebook/50% Desktop, 1 Printer per 10, Speakers and Misc. 167 ft2/Workstation, All Desktop Use, 1 Printer per 10, Speakers and Misc. 125 ft2/Workstation, All Desktop Use, 1 Printer per 10, Speakers and Misc. 125 ft2/Workstation, All Desktop Use, 2 Monitors, 1 Printer Per 10, Speakers and Misc. 85 ft2/Workstation, All Desktop Use, 2 Monitors, 1 Printer Per 8, Speakers and Misc. 85 ft2/Workstation, All Desktop Use, 2 Monitors, 1 Printer Per 8, Speakers and Misc., No Diversity

0.25 0.33 0.40 0.50 0.60 0.80 1.00 1.50 2.00

Table 3: Plug load factors.
34 ASHRAE Journal ashrae.org May 2011



ASHRAE Journal - May 2011

Table of Contents for the Digital Edition of ASHRAE Journal - May 2011

ASHRAE Journal - May 2011
Contents
Commentary
Industry News
Letters
Meetings and Shows
Feature Articles
Seismic Restraint
Plug Load Design Factors
Technology Award Case Studies:
State-of-Art School
Green School Lab
Eco-Friendly, Affordable, School
Building Sciences
Special Section
InfoCenter
Solar NZEB Project
Emerging Technologies
IAQ Applications
Washington Report
International Column
Products
People
Classified Advertising
Advertisers Index
ASHRAE Journal - May 2011 - Intro
ASHRAE Journal - May 2011 - ASHRAE Journal - May 2011
ASHRAE Journal - May 2011 - Cover2
ASHRAE Journal - May 2011 - 1
ASHRAE Journal - May 2011 - 2
ASHRAE Journal - May 2011 - Contents
ASHRAE Journal - May 2011 - Commentary
ASHRAE Journal - May 2011 - 5
ASHRAE Journal - May 2011 - Industry News
ASHRAE Journal - May 2011 - 7
ASHRAE Journal - May 2011 - 8
ASHRAE Journal - May 2011 - 9
ASHRAE Journal - May 2011 - 10
ASHRAE Journal - May 2011 - 11
ASHRAE Journal - May 2011 - 12
ASHRAE Journal - May 2011 - 13
ASHRAE Journal - May 2011 - Letters
ASHRAE Journal - May 2011 - 15
ASHRAE Journal - May 2011 - 16
ASHRAE Journal - May 2011 - 16a
ASHRAE Journal - May 2011 - 16b
ASHRAE Journal - May 2011 - 17
ASHRAE Journal - May 2011 - Meetings and Shows
ASHRAE Journal - May 2011 - 19
ASHRAE Journal - May 2011 - Seismic Restraint
ASHRAE Journal - May 2011 - 21
ASHRAE Journal - May 2011 - 22
ASHRAE Journal - May 2011 - 23
ASHRAE Journal - May 2011 - 24
ASHRAE Journal - May 2011 - 25
ASHRAE Journal - May 2011 - 26
ASHRAE Journal - May 2011 - 27
ASHRAE Journal - May 2011 - 28
ASHRAE Journal - May 2011 - 29
ASHRAE Journal - May 2011 - Plug Load Design Factors
ASHRAE Journal - May 2011 - 31
ASHRAE Journal - May 2011 - 32
ASHRAE Journal - May 2011 - 33
ASHRAE Journal - May 2011 - 34
ASHRAE Journal - May 2011 - 35
ASHRAE Journal - May 2011 - State-of-Art School
ASHRAE Journal - May 2011 - 37
ASHRAE Journal - May 2011 - 38
ASHRAE Journal - May 2011 - 39
ASHRAE Journal - May 2011 - 40
ASHRAE Journal - May 2011 - 41
ASHRAE Journal - May 2011 - 42
ASHRAE Journal - May 2011 - 43
ASHRAE Journal - May 2011 - Green School Lab
ASHRAE Journal - May 2011 - 45
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ASHRAE Journal - May 2011 - 47
ASHRAE Journal - May 2011 - 48
ASHRAE Journal - May 2011 - 49
ASHRAE Journal - May 2011 - 50
ASHRAE Journal - May 2011 - 51
ASHRAE Journal - May 2011 - Eco-Friendly, Affordable, School
ASHRAE Journal - May 2011 - 53
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ASHRAE Journal - May 2011 - 55
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ASHRAE Journal - May 2011 - 57
ASHRAE Journal - May 2011 - Building Sciences
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ASHRAE Journal - May 2011 - 63
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ASHRAE Journal - May 2011 - 65
ASHRAE Journal - May 2011 - 66
ASHRAE Journal - May 2011 - 67
ASHRAE Journal - May 2011 - InfoCenter
ASHRAE Journal - May 2011 - 69
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ASHRAE Journal - May 2011 - 71
ASHRAE Journal - May 2011 - 72
ASHRAE Journal - May 2011 - 73
ASHRAE Journal - May 2011 - 74
ASHRAE Journal - May 2011 - 75
ASHRAE Journal - May 2011 - 76
ASHRAE Journal - May 2011 - 77
ASHRAE Journal - May 2011 - Solar NZEB Project
ASHRAE Journal - May 2011 - 79
ASHRAE Journal - May 2011 - 80
ASHRAE Journal - May 2011 - 81
ASHRAE Journal - May 2011 - 82
ASHRAE Journal - May 2011 - 83
ASHRAE Journal - May 2011 - 84
ASHRAE Journal - May 2011 - 85
ASHRAE Journal - May 2011 - 86
ASHRAE Journal - May 2011 - 87
ASHRAE Journal - May 2011 - 88
ASHRAE Journal - May 2011 - 89
ASHRAE Journal - May 2011 - Emerging Technologies
ASHRAE Journal - May 2011 - 91
ASHRAE Journal - May 2011 - 92
ASHRAE Journal - May 2011 - 93
ASHRAE Journal - May 2011 - 94
ASHRAE Journal - May 2011 - 95
ASHRAE Journal - May 2011 - IAQ Applications
ASHRAE Journal - May 2011 - 97
ASHRAE Journal - May 2011 - 98
ASHRAE Journal - May 2011 - 99
ASHRAE Journal - May 2011 - 100
ASHRAE Journal - May 2011 - 101
ASHRAE Journal - May 2011 - Washington Report
ASHRAE Journal - May 2011 - 103
ASHRAE Journal - May 2011 - International Column
ASHRAE Journal - May 2011 - 105
ASHRAE Journal - May 2011 - 106
ASHRAE Journal - May 2011 - Products
ASHRAE Journal - May 2011 - 108
ASHRAE Journal - May 2011 - People
ASHRAE Journal - May 2011 - Classified Advertising
ASHRAE Journal - May 2011 - 111
ASHRAE Journal - May 2011 - Advertisers Index
ASHRAE Journal - May 2011 - Cover3
ASHRAE Journal - May 2011 - Cover4
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