Utility Scale Rooftop Solar Ability of neighborhood solar

to defer new electrical facilities

1

• Describe Rocky Mountain Power’s in-depth study of neighborhood solar to offset the need to build new infrastructure (power plants, substations and lines)

• Outline Rocky Mountain Power’s progress on Utah carbon reduction goal

• Describe Rocky Mountain Power’s support of customer-owned renewable energy

Purpose of presentation

2

Customer use on the rise• Rocky Mountain Power residential

customers use about 26% more electricity than 20 years ago

• To meet our obligation to serve, additional power supply resources, substations and power lines are needed to meet growing customer use

• New facilities are expensive and difficult to permit

• Advocates want different solutions

3

Can rooftop solar defer new facilities?

Study Area Boundary

• Customers questioned substation expansion in an established neighborhood

• Public opposition delayed conditional use permit

• Undertook subsequent study of rooftop solar to determine its ability to meet customer use

SOUTH TEMPLE

UN

IVER

SITY

STR

EET

1100

EAS

T

400 SOUTH

900

EAST

4

Scope of the solar opportunity

Category Type of BuildingMedian Roof

FootprintMedian # of

PV PanelsMinimum # of

PV PanelsMaximum # of PV Panels

Average Usable Roof Area

Residential Single Family Residential 171 m2 25 0 119 13.81%

Multi-Residential Apartments, Condos, etc. 173 m2 32 0 397 19.88%

Sm. Commercial Restaurant, Commercial Retail 349 m2 136 6 340 31.31%

Lg. Commercial Offices, Hospitals, Churches 430 m2 160 16 917 32.74%

Unknown Unknown Land Use 196 m2 26 2 262 14.57%

20 ft.

40 ft.

60 ft.

80 ft.

5

Determining panel location

176 Panels97.79kWh/day19.8% usable roof

9:30am 12:30pm 6:30pm

• Evaluated roof shading on every structure• Determined solar exposure • Locate solar panels where they produce the most energy

6

• Two-thirds of rooftops are suitable for solar panels (237 of 356 ) • Total number of panels 13,304 • Study uses high efficiency panels; solar energy to electricity = 19%

Study aims to maximize solar output

7

CustomerUse

SolarProduction

Here comes the sun

8

Here comes the sun

CustomerUse

SolarProduction

9

Here comes the sun

CustomerUse

SolarProduction

10

Here comes the sun

CustomerUse

SolarProduction

11

Here comes the sun

CustomerUse

SolarProduction

12

Here comes the sun

CustomerUse

SolarProduction

13

Here comes the sun

CustomerUse

SolarProduction

14

Here comes the sun

CustomerUse

SolarProduction

15

Here comes the sun

CustomerUse

SolarProduction

16

Here comes the sun

CustomerUse

SolarProduction

17

Here comes the sun

CustomerUse

SolarProduction

18

Here comes the sun

CustomerUse

SolarProduction

19

Estimated solar production Solar Energy Conversion:

2,210 MWh annual energy production• 1,560 MWh during summer months (May-Sept.)

Maximum Solar Power Output – as calculated June 21 = 1.52 MW (summer solstice)• Temperature Corrected = 1.45 MW at 76o F

Solar Output on Circuit Peak August 2 = 0.54 MW (2010 circuit peak)

• Temperature Corrected = 0.48 MW at 93o F

Projected 2011 Circuit Peak = 4.6 MVA

20

6:00 am 9:00 am Noon 3:00 pm 6:00 pm 9:00 pm0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

Study areaAugust 2, 2010

Customer Use Solar Production

Meg

awatt

s

Solar contribution to peak

Solar output at ideal conditions

Actual customer load

Circuit Peak

21