approaches for benchmarking energy performance

1

Approaches for Benchmarking Energy Performance

by Terry Sharp

ASHRAE Winter Meeting - 2002

http://www.energystar.gov/http://eber.ed.ornl.gov/benchmark/

2

Benchmarking Approaches

Averages Medians Simple Ranking Normalized Ranking

3

Distributions of Building Energy Use Intensities (EUIs) Are Skewed

0

5

10

15

20

25

20 40 60 80 100 120 160 200

Energy Use Intensity Bin (kBtu/sqft-yr)

Sam

ple

Per

cen

t

Average =90 (62%)

Median =72 (50%)

4

EUIs: Averages Versus Medians

69 69 71

5464

0

20

40

60

80

Location in Distribution

(%)

Median EUI 50 50 50 50 50

Average EUI 69 69 71 54 64

Educ. OfficeLodgeHealth Food

5

Distributions of Building Energy Use Intensities (EUIs) Are Skewed

0

5

10

15

20

25

20 40 60 80 100 120 160 200

Energy Use Intensity Bin (kBtu/sqft-yr)

Sam

ple

Per

cen

t

Average =90 (62%)

Median =72 (50%)

6

A Cumulative Distribution of Building EUIs Can Be Used to Rank

0

20

40

60

80

100

20 40 60 80 100 120 160 200

Energy Use Intensity Bin (kBtu/sqft-yr)

Cu

mu

lati

ve P

erce

nt

7

A Cumulative Distribution Can Serve as a Rating Tool

Electric Use

(kWh)

Other Fuel Use (MMBtu)

860000 2840

Floor Area

(sq-ft)EUI

(kBtu/sf)

103000 114

Rating:

259Sample

size:

51

0

20

40

60

80

100

0 50 100 150 200Energy Use Intensity (kBtu/sf-yr)

Rating

X-- MacAuthur High

Beeks Elem -----XX-- Boone

8

Building Operational Characteristics Impact Energy Use Intensity

1

10

100

1000

10000

0.1 1.0 10.0

Worker Density (number/1000 sqft)

EU

I (k

Btu

/sq

ft-y

r)

9

Drivers of Energy Use

Floor Area

Operating Hours

HDD/ CDD

Occupancy (workers, students,

beds)

Office H M L MSchools H M M HHospitals H NA L HRestaurants M M L HLaboratories H NA L NA

10

A Cumulative Distribution Can Serve as a Rating Tool

Electric Use

(kWh)

Other Fuel Use (MMBtu)

860000 2840

Floor Area

(sq-ft)EUI

(kBtu/sf)

103000 114

Rating:

259Sample

size:

51

0

20

40

60

80

100

0 50 100 150 200Energy Use Intensity (kBtu/sf-yr)

Rating

11

Site and Source Energy Use Conversions

Site basis: 1 kWh = 3.412 Btu

Source basis: 1 kWh = 3.412 x 3.02 = 10.3 Btu

12

For Comparisons, Understanding Site and Source Energy Is Critical

0

40

80

Energy Use Intensity (kBtu/sf-yr)

Rating

Building Type Site Source Site SourceAll Elect (n=310 & 65) 57 173 37 110

Part Elect (n=1065 & 661) 80 175 69 117Difference 40% 1% 89% 6%

Office EUI K-12 School EUI

All electric --

-- Part electric

13

Summary

Beware averages Simple ranking by EUI is a good

approximation for comparisons Ranking where important secondary

drivers are accounted for is best Limited and simple data needed Tools can provide rapid snapshot of cost

reduction / improvement potential