20190821Avista to Staff 148 Attachment A.pdf

2013 Street Light Asset Management Plan
Background
Avista manages street lights for many local and state government entities to provide
lighting for their streets. Some street lights are supplied by metered sources or by an
energy supply only contract which is not covered by this analysis and plan. This plan
covers the ~ 35,000 street lights Avista maintains and provides energy to.
Figure 1 shows by percentage our current population of 35,000 lights by wattage.
Given that 100 watt bulb lights (135 watts for the total fixture consumption) represent
74% of the population, we focused our analysis on just these fixtures. Furthermore, the
only new technology with a cost effective replacement is Light Emitting Diode (LED)
fixtures and can directly replace any of our 100 watt High Pressure Sodium (HPS)
lights. These new LED lights use only 60 watts for the whole fixture, thus saving 75
watts per fixture. Of the 35,000 street lights, ~25,700 are 100 watt HPS lights.
Many of our current street lights replaced the old Mercury Vapor lights in the mid 1980’s
as part of our last light technology conversion. Since their initial installation, street lights
have been maintained by replacing parts such as the bulbs, starter boards, ballasts, and
etc. when they fail. We modeled the current case based on the practices of just
replacing the individual parts as they fail.
Area lights can provide the similar opportunities as street lights. Avista’s system has
17,710 area lights in addition to street lights. Many of these area lights could also be
converted to LED fixtures. However, our customers will determine the need and when
they convert from HPS to LED fixtures. Predicting customers’ adoption of LED fixtures
is difficult and beyond this analysis. LED fixtures will replace HPS lights as area lights
over time and provide savings to our customers but is beyond the scope of this analysis.
As part of the analysis, we examined the current practices and compared them with a
planned bulb and photocell replacement of existing HPS and changing the technology
to LED lights. Our goal is to identify the best strategy for managing the street lights.
Staff_PR_148 Attachment A Page 1 of 11

Trends and Analysis
In 2012
Street lights. Figure 2 shows
main constituents of

Figure 1
We then analyzed the material usage to see what it indicated about how long the main
components were lasting. We calculated the replacement ratio for one year’s worth of
data to estimate a Mean Time to Failure (MTTF) by dividing the amount of material use
by the number of associated fixtures to get the Replacement Ratio. Since this was one
year’s worth of data, the MTTF was simply the inverse of the Replacement Ratio and
Table 1
equipment.

150 watt
0%
21%
250 watt
3%
1%
Street Light Quantity by Current Wattage
, we performed detailed analysis to understand the current state of Area and
one of the results of the analysis
Figure 2.
, Street Light Population by Wattage
We then analyzed the material usage to see what it indicated about how long the main
components were lasting. We calculated the replacement ratio for one year’s worth of
data to estimate a Mean Time to Failure (MTTF) by dividing the amount of material use
by the number of associated fixtures to get the Replacement Ratio. Since this was one
year’s worth of data, the MTTF was simply the inverse of the Replacement Ratio and
shows the results of these calculations. While the results in Table
one year’s worth of data, the MTTF for Lamps and photocells are consistent with other
data used in our models. However, this data only reflects the performance of
equipment previously installed and does not necessarily reflect the performance of new
100 watt
74%
400 watt
1%
Street Light Quantity by Current Wattage
, we performed detailed analysis to understand the current state of Area and
using data from 2011,

d
1 only reflect
Street Light Quantity by Current Wattage
Staff_PR_148 Attachment A Page 2 of 11

Figure 2

Table 1
Component
Groups
Quantities
fixture 271
641
7,930
5,151
1,126
fixture 683
Note: In 2011,
37,702 fixtures

Figure 3
the pa
for O&M
Labor, $33
, 2011 Cost Breakdown of the $92 per HPS Fixture Maintenance
Estimate b
O&M and Capital
Combined
Material Usage
Quantities
Replacement
Ratio
MTTF
(Years)
271 2% 60
1% 84
15% 7
10% 10
2% 48
2% 55
16,156
Figure
1 million
Figure 3) and below
Material,
$10

ased on Material Usage for Area and Street Lights
fixtures and Street Light Population =
3. Based on

Material,
Overheads,
$28
Staff_PR_148 Attachment A Page 3 of 11

Figure 3, Historical Spending Trends on Area and Street Lights
Alternatives Examined
For this analysis, we examined three different cases. The current case or Base Case
replaces failed street light components only when they fail. The second case, called the
LED Case, replaces the current HPS lights with new LED lights and implements a
planned replacement at 15 years for the fixture and photocell. We should note that
inside the new LED model, a 15 year replacement strategy proved more cost effective
over the lifecycle than running LED lights to failure. The final case represents keeping
the current HPS lights and performing planned replacements of the bulbs and
photocells at 5 year cycles for the bulbs and 10 year cycle for the photocells. The last
case is called the Optimized Case.

Key Assumptions and Data
The Current Case and the Optimized Case for HPS lights uses the same failure
characteristics shown in Table 2. The values in Table 2 come from actual failure
information plotted on failure curves inside the model and then calculated by the model
software. Table 3 shows the failure characteristics assumed for LED fixtures and
components based on manufacturer’s information and an assumed failure shape
characteristic.
-
200
400
600
800
1,000
1,200
1,400
1,600
2008 2009 2010 2011 2012 7/12 -
6/13Ar
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($
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Th
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Year
Area and Street Light Historical Spending
with Test Year
O&M Area O&M Street Capital Area
Capital Street Linear (O&M Street)
Staff_PR_148 Attachment A Page 4 of 11

Table 2, HPS Light Component Failure Characteristics
Component
10% of the initial
population will
have failed by ____
Years
20% of the initial
population will
have failed by
____ Years
Mean Time to Failure
(50% of the initial
population will have
failed by ____ Years)
100 W Bulb 3.4 4.4 6.7
Current
Photocells 5.7 7.3 10.6
100 W Starter
Board 7.4 10.5 16.3

Table 3, Assumed LED Light Component Failure Curves
Component population will
have failed by
____ Years
population will
have failed by
____ Years
(50% of the initial
population will have
failed by ____ Years)
New Style Photocell 7.9 10.2 14.9
LED Light Fixture 12.1 15.5 22.6

Table 4 shows the risks associated with a street light failure. In Table 4, the average
number of light failures per consequence indicates how many light failures on average
occur each time you realize the consequence. These risks are used in all three cases
examined. An S1 risk represents the potential of injury due to a street light being out.
An S4 risk represents a very serious to fatal accident where a street light could have
contributed to the accident. The Theft risk represents the loss of personal property
when a street light is out.

Table 4, Risks associated with Street Light Failures
ID Average Number of Light Failures per Consequence
S1 - Modified 29,412
S4 - Modified 50,000
Theft 5,000

Staff_PR_148 Attachment A Page 5 of 11

fixture.
Figure 4
Model Results
For each of the cases, we developed and ran a model to help compare the risks,
resource needs, potential energy savings, and financial impa
Examining all of these factors, Avista select the best strategy from the three different
cases for our Street Lights.

since the LED co
higher level of risk.
Overheads,
$123
Labor, $68
Based on our analysis, we estimated that it will cost $450 per fixture to replace an
existing HPS light with a new LED light. Figure 4
, LED Replacement Cost Breakdown of the $450 per Fixture
For each of the cases, we developed and ran a model to help compare the risks,
resource needs, potential energy savings, and financial impacts of each case.
Examining all of these factors, Avista select the best strategy from the three different
The first factor to consider is the associated risk with each case. Table
Table 5
Material,
$199
Based on our analysis, we estimated that it will cost $450 per fixture to replace an
shows the cost breakdown on each

shows the
Material,
Staff_PR_148 Attachment A Page 6 of 11
Table 5, Number of Occurrences’ by Risk for all Three Cases over a 25 year Timeframe
ID Base
Case Case Case
Modified
6.7 0.8 2.1
S4 -
Modified
3.9 0.5 1.3
Theft 39.3 4.7 12.5
In comparing resources as shown in Table 6, the LED Case shows a five year
conversion timeframe followed by 10 years of reduced effort until the next planned
replacement point at 15 years. Averaged over 25 years, the LED Case average number
of annual man-hours is only 3,200 hours and an average of 1,800 equipment-hours.
The reduced man-hours and equipment-hours contribute to savings for the LED Case
compared to the other two cases. Table 6 also shows that the implementation of the
LED Case will require only one additional Full Time Employee (FTE) to implement along
with one additional vehicle over a five year period.
Table 6, Resource Comparisons
Unit of
Comparison Base Case LED Case Optimized Case
Average Annual
Labor Man-Hours 5,200
7,000 (Years 1-5)
1,200 (Years 6-15)
3,200 Average
5,000
Average Annual
Equipment Hours 2,600
4,000 (Years 1-5)
700 (Years 6-15)
1,800 Average
2,700
As discussed above, each 100 watt HPS light replaced will save 75 watts per fixture.
As shown in Equation 1, once all of the 100 watt HPS street lights are replaced, the
annual energy savings will be 8,500 MWH each year.
Equation 1:
 
 

 =   ∗ , 
 ∗ ,   

 = ,! "# / 
While the risks and the average resource requirements are lower for the LED Case, the
cost of maintaining or replacing a LED fixture costs significantly more. Figure 2 and
Figure 4 show that an LED fixture costs $360 more compared to a HPS light to
maintain. However, the costs to replace a LED fixture represents a capital cost since
we would replace a retirement unit (the whole fixture since all internal components have
Staff_PR_148 Attachment A Page 7 of 11

the same expected life) where work on HPS lights is a O&M expense. Replacing HPS
lights with LED fixtures creates an O&M offset.

Given all of the information above, Table 7 shows the financial analysis of all three
models. From a financial perspective, the Optimized Case provides the best value to
our customers by keeping costs the lowest. The LED Case does provide a better value
than our current case, so it will provide savings to our customers but not as much as the
Optimized Case. The key factors driving the results are material costs and the
expected life of LED fixtures, so the LED Case is sensitive to changes in these values.
We anticipate the cost of the LED fixtures to continue down to around $150 in the near
future and the life of the fixture to continue to increase. Both of these factors would
improve the financial performance of the LED Case but were not included in the model
to be conservative. Currently, the new photocell drives our optimized replacement at a
15 year interval. If the new photocells prove more reliable than estimated, we would
extend the replacement interval beyond 15 years and further improve the value of the
LED Case. Over a 25 year period, the LED Case will eventually save money over the
Optimized case as shown in Figure 5. However, the initial conversion costs are very
high and have the greatest impacts on the financial results.

Table 7, Financial Comparisons
Model Customer IRR Levelized Gr. Mar.
Requirement
Base Case 5.62% $2,462,508
LED Case 8.46% $2,178,537
Optimized Case 12.12% $1,667,126

Staff_PR_148 Attachment A Page 8 of 11

Figure 5, Cumulative Cost Comparisons
Selected Strategy
Given that the LED Case will save our customers money over the Base Case or current
case, we selected to begin converting our 100 watt HPS lights to LED fixtures beginning
in 2015. While the Optimized Case provides a better financial return to our customers,
the energy savings associated with the LED lights becomes the main driver. The
customers will still see savings over the life of the LED fixtures compared to today’s
practices and eliminate the need for 1.9 MW of generation at night (75 Watt Savings per
fixture * 25,758 fixtures = 1.9 MW).

In order to implement the LED Case, Avista will submit a new rate schedule for LED
street lights for implementing in 2015. The plan is to replace all 100 watt HPS fixtures
over a 5 year period. This will replace fixtures in planned areas and fixtures as they fail.
This will put more fixtures replaced in the first few years and less in the outer years.
Pro Forma
Based on a test year of July 1st, 2012 through June 30th, 2013, we anticipate the O&M
savings will be $488,000 (see Table 8 for details). A five year plan to replace HPS
street lights with LED fixtures will add $2.32 million per year to the current capital
spending for five years. Table 9 does show that we anticipate more than the $488,000
$
$10
$20
$30
$40
$50
$60
$70
0 2 4 6 8 10 12 14 16 18 20 22 24
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Years
Base Case LED Case Optimized Case
Staff_PR_148 Attachment A Page 9 of 11

in O&M spending over time, but the test year used in the rate case had below average
spending on O&M as shown above in Figure 3.

Table 8, Pro Forma for LED Conversion of Street Lights
Year Spending/Budget Spending/Budget
$979,002 $681,516
$3,298,250 $193,824
-$2,319,248 $487,692

Table 9, Projected Planned Capital Budgets and O&M Budgets for Street Lights
Year Budget
with LED
Conversion
O&M Budget
with LED
Conversion
O&M Budget
without LED
Conversion
O&M Offset
with LED
Conversion
2015 $2,319,248 $193,824 $732,012 $538,188
2016 $2,323,370 $198,241 $746,652 $548,411
2017 $2,335,605 $203,970 $761,585 $557,615
2018 $2,354,418 $210,732 $776,817 $566,085
2019 $2,393,676 $220,542 $792,353 $571,811
2020 $97,159 $228,035 $808,200 $580,165
2021 $140,218 $238,563 $824,364 $585,801
2022 $225,059 $255,240 $840,852 $585,612
2023 $291,367 $269,314 $857,669 $588,354
2024 $330,003 $279,462 $874,822 $595,360
2025 $411,862 $295,973 $892,318 $596,346
2026 $496,398 $312,965 $910,165 $597,200
2027 $544,068 $324,702 $928,368 $603,666
2028 $646,035 $344,414 $946,935 $602,521
2029 $704,571 $357,923 $965,874 $607,952
2030 $2,059,519 $264,983 $985,192 $720,209
2031 $2,118,200 $274,195 $1,004,895 $730,700
2032 $2,144,239 $282,089 $1,024,993 $742,905
2033 $2,178,558 $291,200 $1,045,493 $754,293
2034 $2,263,814 $304,680 $1,066,403 $761,724
2035 $277,074 $318,617 $1,087,731 $769,114
2036 $334,083 $330,312 $1,109,486 $779,174
Staff_PR_148 Attachment A Page 10 of 11

Year Budget
with LED
Conversion
O&M Budget
with LED
Conversion
O&M Budget
without LED
Conversion
O&M Offset
with LED
Conversion
2037 $444,031 $345,078 $1,131,676 $786,598
2038 $522,725 $355,799 $1,154,309 $798,510
2039 $603,525 $371,337 $1,177,395 $806,058

Summary
In summary, the selected strategy for managing 100 watt HPS street lights is to replace
them over five years with LED fixtures. Given the impacts on risk, resource needs,
energy savings, and financial results, we believe converting to LED lights provides a
good return to our customers and significant energy savings reducing the need for
future generation capacity.
Staff_PR_148 Attachment A Page 11 of 11