Monitoring & Verification Methodologies
1.0 Monitoring & Verification
Energy Measurement and Verification (M&V) is defined as the process
of measuring and verifying both energy and cost savings produced as a result of
the implementation of DSM measures. The need for cost effective M&V has become
critical because of reduced government funding of energy conservation measures and
the increased funding of these programs by the private sector through energy savings
performance contracting and demand side management (DSM). Effective M&V is the
only means of determining if the contractor is performing well, and to check DSM
measures are generating the expected level of cost savings. This process will determine
how much the government has saved, and how much the government must pay the contractor.
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2.0 Principles of M&V
The fundamental principles of good M&V practice are described below:
Accurate M&V reports should be as accurate as the M&V budget will allow.
M&V costs should normally be small relative to the monetary value of the savings
being evaluated. M&V expenditures should also be consistent with the financial
implications of over- or under-reporting of a project’s performance. Accuracy tradeoffs
should be accompanied by increased conservativeness in any estimates and judgements.
Complete The reporting of energy savings should consider all effects of a project.
M&V activities should use measurements to quantify the significant effects,
while estimating all others.
Conservative Where judgements are made about uncertain quantities, M&V procedures
should be designed to under-estimate savings.
Consistent The reporting of a project’s energy effectiveness should be consistent
between:
different types of energy efficiency projects;
different energy management professionals for any one project;
different periods of time for the same project;
and energy efficiency projects and new energy supply projects.
‘Consistent’ does not mean ‘identical,’ since it is recognized that any empirically
derived report involves judgments which may not be made identically by all reporters.
By identifying key areas of judgment, M&V helps to avoid inconsistencies arising
from lack of consideration of important dimensions. Relevant The determination of
savings should measure the performance parameters of concern, or least well known,
while other less critical or predictable parameters may be estimated.
3.0 M&V Framework & Options
Energy, water or demand savings cannot be directly measured, since savings
represent the absence of energy/water use or demand. Instead, savings are determined
by comparing measured use or demand before and after implementation of a program,
making suitable adjustments for changes in conditions.
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As an example of savings determination process, above figure shows the energy-usage
history of an industrial boiler before and after the addition of an energy conservation
measure to recover heat from its flue gases. At about the time of energy conservation
measure installation, plant production also increased.
To properly document the impact of the energy conservation measure, its energy effect
must be separated from the energy effect of the increased production. The “baseline
energy” use pattern before energy conservation measure installation was studied
to determine the relationship between energy use and production. Following energy
conservation measure installation, this baseline relationship was used to estimate
how much energy the plant would have used each month if there had been no ECM (called
the “adjusted-baseline energy”). The saving, or ‘avoided energy use’ is the difference
between the adjusted-baseline energy and the energy that was actually metered during
the reporting period.
Without the adjustment for the change in production, the difference between baseline
energy and reporting period energy would have been much lower, under-reporting the
effect of the heat recovery.
It is necessary to segregate the energy effects of a savings program from the effects
of other simultaneous changes affecting the energy using systems. The comparison
of before and after energy use or demand should be made on a consistent basis, using
the following general Equation:
Savings = (Baseline-Period Use or Demand - Reporting-Period Use or Demand) ± Adjustments
The "Adjustments" term in this general equation is used to re-state the use or demand
of the baseline and reporting periods under a common set of conditions. This adjustments
term distinguishes proper savings reports from a simple comparison of cost or usage
before and after implementation of an energy conservation measure (ECM). Simple
comparisons of utility costs without such adjustments report only cost changes and
fail to report the true performance of a project. To properly report “savings,”
adjustments must account for the differences in conditions between the baseline
and reporting periods.
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IPMVP Option
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How Savings Are
Calculated
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Typical Applications
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A. Retrofit
Isolation: Key Parameter Measurement
Savings are determined by field measurement of the
key performance parameter(s) which define the energy use of the ECM’s affected system(s)
and/or the success of the project.
Measurement frequency ranges from short-term to continuous,
depending on the expected variations in the measured parameter, and the length of
the reporting period.
Parameters not selected for field measurement are
estimated. Estimates can based on historical data, manufacturer’s specifications,
or engineering judgment. Documentation of the source or justification of the estimated
parameter is required. The plausible savings error arising from estimation rather
than measurement is evaluated.
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Engineering calculation of baseline and reporting period energy from:
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short-term or continuous measurements of key operating parameter(s); and
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estimated values. Routine and non-routine
adjustments as required.
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A lighting retrofit where power draw is the key performance parameter that is measured
periodically. Estimate operating hours of the lights based on building schedules
and occupant behavior.
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B. Retrofit Isolation: All Parameter
Measurement
Savings are determined by field measurement of the energy use of the ECM-affected
system. Measurement frequency ranges from short-term to continuous, depending on
the expected variations in the savings and the length of the reporting period.
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Short-term or continuous measurements of baseline and reporting period energy, and/or
Engineering computations using measurements of proxies of energy use. Routine and
non-routine adjustments as required.
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Application of a variable speed drive and controls to a motor to adjust pump flow.
Measure electric power with a kW meter installed on the electrical supply to the
motor, which reads the power every minute. In the baseline period this meter is
in place for a week to verify constant loading. The meter is in place throughout
the reporting period to track variations in power use.
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C. Whole Facility
Savings are determined by measuring energy use at the whole facility or sub-facility
level. Continuous measurements of the entire facility’s energy use are taken throughout
the reporting period.
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Analysis of whole facility baseline and reporting period (utility) meter data. Routine
adjustments as required, using techniques such as simple comparison or regression
analysis. Non-routine adjustments as required.
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Multifaceted energy management program affecting many systems in a facility. Measure
energy use with the gas and electric utility meters for a twelve month baseline
period and throughout the reporting period.
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D. Calibrated Simulation
Savings are determined through simulation of the energy use of the whole facility,
or of a sub-facility.
Simulation routines are demonstrated to adequately model actual energy performance
measured in the facility.
This Option usually requires considerable skill in calibrated simulation.
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Energy use simulation, calibrated with hourly or monthly utility billing data. (Energy
end use metering may be used to help refine input data.)
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Multifaceted energy management program affecting many systems in a facility but
where no meter existed in the baseline period.
Energy use measurements, after installation of gas and electric meters, are used
to calibrate a simulation.
Baseline energy use, determined using the calibrated simulation, is compared to
a simulation of reporting period energy use.
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4.0 M&V Plan & Contents
The preparation of an M&V Plan is a recommended part of savings determination.
Advance planning ensures that all data
needed for savings determination will be
available after implementation of the ECM(s), within an acceptable budget. Data
from the baseline and details of the ECMs may be lost over time. Therefore record
them for future reference in case conditions change or ECMs fail. Documentation
should be easy to find and easy to understand by verifiers and others, because years
may pass before these data are needed.
A complete M&V Plan should include discussion of the following 13 topics:
ECM Intent Describe the ECM, its intended result, and the commissioning
procedures that will be used to verify successful implementation of each
ECM. Identify any
planned changes to conditions of the baseline, such as unoccupied building
temperature settings.
Selected IPMVP Option and Measurement Boundary Specify which M&V Option
will be used to determine savings. Identify the measurement boundary of the
savings determination. The boundary may be as narrow as the flow of energy
through a
pipe or wire, or as broad as the total energy use of one or many buildings.
Describe the nature of any interactive effects beyond the measurement boundary
together
with their possible effects. Baseline: Period, Energy and Conditions Document the facility’s
baseline conditions and energy data, within the measurement boundary. (In
energy performance
contracts, baseline energy and baseline conditions may be defined by either
the owner or the ESCO, thus providing the other party is given adequate opportunity
to verify them.) An energy audit used for establishing the objectives of
a savings
program or terms of an energy performance contract usually provides most
if not all of the baseline documentation needed in the M&V Plan. This
baseline documentation should include:
Identification of the baseline period All baseline energy consumption and demand data All independent variable data coinciding with the energy data (e.g.
production rate, ambient temperature) All static factors coinciding with the energy data:
Occupancy type,
density and periods
Operating conditions for each baseline operating period
and season, other than the independent variables. (For example, in an
industrial process, baseline
operating conditions might include product type(s), raw material type, and
number of production shifts per day. In a building baseline operating conditions
might include light level, space temperature humidity and ventilation levels.
Description of any baseline conditions that fall short of required conditions.
For example, the space is under-heated during the baseline, but the ECM will
restore the desired temperature. Details of all adjustments that are necessary
to the baseline energy data to reflect the energy-management program’s
expected improvement from baseline conditions.
Size, type, and insulation of any relevant building envelope elements such
as walls, roofs, doors, windows.
Equipment inventory: nameplate data, location, condition. Photographs or videotapes
are effective ways to record equipment condition.
Equipment operating practices
(schedules and setpoints, actual temperatures and pressures)
Significant equipment
problems or outages during the baseline period. The baseline documentation
typically requires well-documented audits, surveys,
inspections and/or short-term metering activities. The extent of this information
is determined by the measurement boundary chosen or the scope of the savings
determination. Where whole-facility M&V methods are employed, all facility
equipment and conditions should be documented.
Reporting Period Identify
the reporting period. This period may be as short as an instantaneous measurement
during commissioning of an ECM, or as long
as the time required to recover the investment cost of the ECM program. Basis for Adjustment Declare the set of conditions to which all energy
measurements will be adjusted. The conditions may be those of the reporting
period or some other set of fixed conditions. As discussed, this choice determines
whether savings are reported as avoided energy or as normalized savings. Analysis Procedure Specify the exact data analysis procedures, algorithms
and assumptions to be used in each savings report. For each mathematical
model used, report all of its terms and the range of independent variables
over which
it is valid. Energy Prices Specify the energy prices that will be used
to value the savings, and whether and how savings will be adjusted if prices
change in future. Meter Specifications Specify the metering points and
period if metering is not continuous. For non-utility meters, specify:
meter characteristics,
meter reading and witnessing protocol, meter commissioning procedure, routine
calibration process, and method of dealing with lost data. Monitoring Responsibilities
Assign responsibilities for reporting and recording the energy data, independent
variables and static factors within the measurement
boundary during the reporting period. Expected Accuracy Evaluate the expected
accuracy associated with the measurement, data capture, sampling and data
analysis. This assessment should include qualitative
and any feasible quantitative measures of the level of uncertainty in the
measurements and adjustments to be used in the planned savings report. Budget Define the budget and the resources required for the savings
determination, both initial setup costs and ongoing costs throughout the
reporting period.
Report Format Specify how results will be reported
and documented. A sample
of each report should be included. Quality Assurance Specify quality-assurance
procedures that will be used for savings reports and any interim steps
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5.0 M&V Reporting
M&V Reports should be prepared and presented as defined in the M&V
Plan. Complete M&V reports should include at least:
Observed data of the reporting period: the measurement period start and end points
in time, the energy data, and the values of the independent variables Description
and justification for any corrections made to observed data For Options the agreed
estimated values Energy price schedule used All details of any baseline non-routine
adjustment performed. Details should include an explanation of the change in conditions
since the baseline period, all observed facts and assumptions, and the engineering
calculations leading to the adjustment.
Computed savings in energy and monetary units. M&V reports should be written
to their readers’ levels of understanding. Energy managers should review the M&V
reports with the facility’s operating staff. Such reviews may uncover useful information
about how the facility uses energy, or where operating staff could benefit from
more knowledge of the energy-consumption characteristics of their facility.
6.0 M&V Issues
6.1 Applying Energy Prices
Cost savings16 are determined by applying the appropriate price schedule in
the following equation:
Cost Savings = Cb – Cr 2)
Where:
Cb = Cost of the baseline energy plus any adjustments17
Cr = Cost of the reporting period energy plus any adjustments
Costs should be determined by applying the same price schedule in computing
both Cb and Cr. When the conditions of the reporting period are used as the
basis for reporting energy savings, the price schedule of the reporting period
is normally used to compute “avoided cost.
6.2 Baseline Adjustments
Conditions, which vary in a predictable fashion and are significant to energy
use within the measurement boundary, are normally included within the mathematical
model used for routine adjustments. Where unexpected or one-time changes
occur in conditions within the measurement boundary, which are otherwise
static (static factors), nonroutine adjustments, also called baseline adjustments,
must be made.
Non-routine adjustments are needed where a change occurs to equipment or operations
within the measurement boundary after the baseline period. Such change occurs
to a static factor not to independent variables. For example, an ECM improved
the efficiency of a large number of light fixtures. When more light fixtures
were installed, after ECM installation, a non-routine adjustment was made.
The estimated energy of the extra fixtures was added to the baseline energy
so that the ECM’s true savings were still reported.
6.3 Role of Uncertainty
The measurement of any physical quantity includes errors because no measurement
instrument is 100% accurate. Errors are the differences between observed
and true energy use. In a savings-determination process, errors prevent the
exact determination of savings.
Characteristics of a savings determination process which should be carefully
reviewed to manage accuracy or uncertainty are:
Instrumentation – measurement equipment errors are due to calibration,
inexact measurement, or improper meter selection installation or operation.
Modeling – the inability to find mathematical forms that fully account
for all variations in energy use. Modeling errors can be due to inappropriate
functional form, inclusion of irrelevant variables, or exclusion of relevant
variables.
Sampling – use of a sample of the full population of items or events
to represent the entire population introduces error as a result of: the variation
in values within the population, or biased sampling. Sampling18 may be done
in either a physical sense (i.e., only 2% of the lighting fixtures are measured)
or a temporal sense (instantaneous measurement only once per hour).
Interactive effects (beyond the measurement boundary) that are not fully included
in the savings computation methodology.
Estimation of parameters using Option A, rather than measurement. You can minimize
the variation between the parameter’s estimated value and its true value
through careful review of the ECM design, careful estimating of the parameter,
and careful ECM inspection after installation.
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7.0 References
Akbari, H., Heinemeier, K.E., LeConiac, P. and Flora, D.L. 1988. "An
Algorithm to Disaggregate Commercial Whole-Facility Hourly Electrical Load
Into End Uses", Proceedings of the ACEEE 1988 Summer Study on Energy Efficiency
in Buildings, Vol. 10, pp. 10.14-10.26.
ASHRAE Guideline 1-1996. The HVAC Commissioning Process. American Society of
Heating, Ventilating, and Air Conditioning Engineers, Atlanta, Georgia.
ASHRAE Guideline 14-2002, Measurement of Energy and Demand Savings. American
Society of Heating, Ventilating, and Air Conditioning Engineers, Atlanta, Georgia.
ASHRAE. 1989. An Annotated Guide to Models and Algorithms for Energy Calculations
Relating to HVAC Equipment, American Society of Heating, Ventilating, and Air
Conditioning Engineers, Atlanta, Georgia.
International Performance Measurement & Verification Protocol developed
by Efficiency Valuation Organization.
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