Weather Normalization

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Weather Normalization Presented by John
Avina Abraxas Energy Consulting
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OUTLINE

• Why
• How
• Reading Bills to Understand Building
• Humidity
• Benchmarking with Normalization

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Retail in Wisconsin
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Retail in Wisconsin
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• Average Weather.
• Average of all the high and low temperatures
  during the billing period

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Retail in Wisconsin
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Retail in Wisconsin
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Retail in Wisconsin
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Retail in Wisconsin
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Retail in Wisconsin
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Retail in Florida
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Retail in Florida
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Retail in Florida
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Retail in Florida
Cooling Balance Point 60
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Retail in Florida
Cooling Balance Point 67
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Retail in Minnesota
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Retail in Minnesota
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College in Boston
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College in Boston
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Retail in San Francisco
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Recap Why Use Weather?
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M and V Standards

• International Performance Measurement and
  Verification Protocol

www.ipmvp.org
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M and V Standards

• Federal Energy Management Guidelines

http//www.eere.energy.gov/femp/pdfs/26265_seci.pd
f
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M and V Standards

• ASHRAE Guideline 14

http//www.ashrae.org
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IPMVP MV Options

• 4 Methods of M V
• Option A - Partially Measured Retrofit Isolation
• Option B - Retrofit Isolation
• Option C - Whole (or Part) Building (Utility
  Bills)
• Option D Calibrated Simulation
• Methods chosen based upon budget, need for
  accuracy, ECMs installed, Metering Setup

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IPMVP MV Options

• Option A - Partially Measured Retrofit Isolation
• Partial short-term/continuous measurements some
  but not all stipulated
• For Separable ECM Savings Determination -
  Lighting

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IPMVP MV Options

• Option B - Retrofit Isolation
• Full short-term or continuous field measurement -
  no stipulations
• For Separable ECM Savings Determination - HVAC
  subsystem

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IPMVP MV Options

• Option C - Whole (or Part) Building
• Full continuous energy use and demand measurement
  during Baseline and Post- Retrofit Periods
• Collective Savings of all ECMs for Area monitored
  by a Single Meter

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IPMVP MV Options

• Option D Calibrated Simulation
• Computer-based simulation of energy use of
  building components
• Simulation Calibration, Considerable skills,
  Costly ????

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MV and Utility Bill Analysis

• Suppose an ESCO chooses Option C,
• Utility Bill Analysis...
• Why would an ESCO want to correct for weather
• Why Not keep it simple and just compare pre and
  post retrofit bills
• Billions of Dollars of savings are tracked using
  Option C

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Why Utility Bills Dont Always Yield Savings?
Suppose an ESCO expected this from a Chiller
Retrofit.
Savings
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Why Utility Bills Dont Always Yield Savings?
and instead got this.
Increase
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Seen Him Before?
Why Arent There Any Savings? What Do We Tell
the Customer? Will I Keep My Job? Will I Get My
Bonus?
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The ESCOs Dilemma
How Can They Show Savings This Year?
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The ESCOs Dilemma
How Can They Show Savings This Year?
Real Data
Cooling kWh CDD Which means double CDD
? double Cooling kWh
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Retail in Minnesota
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How to Perform Weather Normalization
Start with Bills and Weather Data
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Using Weather toUnderstand Bills

• Determine How Bills Vary with Weather

Electric used to Heat Cool
Electric used to Cool Only
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• Estimate Balance Point

Temperature Sensitive Usage
Non-Temperature Sensitive Usage
Balance Point
Cooling Balance Point is the Temperature at which
the Building Starts to Cool. Low Cooling Balance
Points indicate Outside Air is NOT being used for
Free Cooling.
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• Estimate Balance Point

Temperature Sensitive Usage
Non-Temperature Sensitive Usage
Balance Point
Balance Point is the Temperature at which the
Building Starts to Heat.
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Calculate Cooling Degree Days

• For each day in Billing period
• CDDi(Ave Outside Temp - Bal Point Temp) X
  1day
• Where Ave Outside Temp is the average
  between high and low temperature for the day.
• And Bal Point Temp (balance point
  temperature) is the balance point found in the
  previous slide.
• You cannot have negative CDDs
• 2. CDDBilling Period S(CDDi)

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Calculate Heating Degree Days

• For each day in Billing period
• HDDi(Bal Point Temp - Ave Outside Temp) X
  1day
• Where Ave Outside Temp is the average
  between high and low temperature for the day.
• And Bal Point Temp (balance point
  temperature) is the balance point found in the
  previous slide.
• You cannot have negative HDDs
• 2. HDDBilling Period S(HDDi)

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Weather Normalization
Perform a Linear Regression between Energy Usage
and CDD (and/or) HDD. Find the best fit line.
This is the Cooling Balance Point. Cooling
Balance Point is the temperature at which the
building starts cooling.
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Normalization Tools

• You can use Excel or Canned Software
• There are Several Desktop applications that
  handle weather Normalization, one of which
  specializes in it.

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Understanding the Baseline

• Your Fit Line Has an Equation, which is called
  the Baseline Equation

y mx b
which could be rephrased into something like this
kWh 61.986 x CDD 1872.7 x days
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Energy Balance
Use the Regression Coefficients to True Up Energy
Balance
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Understanding the Baseline

• Your Fit Line Has an Equation, which is called
  the Baseline Equation

Baseline Equation Best Fit Line Base Year
Bills So now we can work with the Baseline
Equation and throw out the bills. We dont need
them any more. Baseline Equation represents your
energy usage patterns during your Base Year
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Understanding the Baseline

• What Good is the Equation?

We take a Current Year Bill, determine of days
in the bill, determine of CDD (or HDD) and
plug those into the Baseline Equation.
7/21/05 Bill 100,000 kWh 700 CDD 30 days
Baseline kWh 61.986 x CDD 2872.7 x days
Baseline kWh (61.986 x 700) (2872.7 x 30)
Baseline kWh 129,571 kWh
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Understanding the Baseline

• What Good is the Equation?

So Baseline kWh represents how much energy your
facility would have used this year given current
weather conditions and Base Year usage
patterns. The Baseline Equation represents Base
Year Usage patterns, and we applied Current Year
weather to it
7/21/05 Bill 100,000 kWh 700 CDD 30 days
Baseline kWh 61.986 x CDD 2872.7 x days
Baseline kWh (61.986 x 700) (2872.7 x 30)
Baseline kWh 129,571 kWh
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Understanding the Baseline

• What Good is the Equation?

Savings is Baseline Usage the Actual Bill Usage
Baseline kWh 61.986 x CDD 2872.7 x days
Baseline kWh (61.986 x 700) (2872.7 x 30)
Baseline kWh 129,571 kWh
7/21/05 Bill 100,000 kWh 700 CDD 30 days
Savings Baseline kWh - Actual kWh
Savings 129,571 kWh 100,000 kWh
Savings 29,571 kWh
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Savings then
Savings Baseline Actual Which is how much
we would have used how much we did use

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Wait a Second!
You dont have to do all this math!
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Wait a Second!
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Reading Bills
temperature sensitive usage
non-temperature sensitive usage
Starts cooling at 46 degrees? Runs on a working
control system Very large non-temperature
sensitive usage
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Reading Bills
Correlation to HDD Much Noisepoor control
operation or dont understand the meter Starts
heating at 65 F degrees
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More

• You Can Normalize with More than Just Weather.

• Normalize to
• Production,
• School Calendar,
• Occupancy
• Or Something else

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Normalizing with Humidity
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LOAD FACTOR
Load Factor is a measure of demand relative to
usage. It can indicate how the building is
using energy.
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LOAD FACTOR
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LOAD FACTOR

• LF 1 implies uniform levels of use (no high
  peak demand)
• LF 0.2 implies very high peak demands

LF gives an idea where energy manager
should focus. If LF is high (above .7), focus
on reducing usage, not demand.
kW
Hour of the Day
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LOAD FACTOR
Billing error?
Change in Usage Pattern
Why is the purple line the highest?