Measurement and Verification Options for Federal Energy- and Water-Saving Projects

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Federal Energy Management Program measurement and verification (M&V) guidelines and International Performance Measurement and Verification Protocol M&V methodologies are broken into four options. These options offer generic M&V approaches for energy- and water-saving projects.

The four options provide a range of M&V approaches to employ depending on the characteristics of the energy conservation measures (ECMs).

Option A: Retrofit Isolation Approach

Option A is a retrofit isolation approach designed for projects in which the potential to generate savings must be verified, and the actual savings can be determined from limited data collection, engineering calculations, and stipulated factors. Baseline and post-installation energy uses are estimated using an engineering analysis of measurements of the most critical parameter of energy usage.

The intent of Option A is to verify performance through pre- and post-retrofit measurements. An individual system is measured and any potential interactions with other systems are disregarded. Use factors can be measured once (in the baseline period) or determined based upon engineering estimates, operating schedules, operator logs, typical weather data, or other documented information sources. The selection of which factors to measure should be considered relative to the contractor’s responsibilities.

After postretrofit measurements, annual inspections verify that the project has the “potential to perform." Measurements of the key parameter may or may not continue throughout the term of the contract. The level of accuracy of the calculated savings depends on the validity of the assumptions and the measurements that are made.

Option B: Retrofit Isolation or System-Level Approach

Measurements of performance and operational factors provide long-term persistence data on the energy use of the equipment or system. Measurements may be short-term, periodic, or continuous.

Option B is a retrofit isolation or system-level approach. Option B is similar to Option A but involves the measurement of all relevant parameters. This method is intended for retrofits with performance factors and operational factors that can be measured at the component or system level. Short-term periodic measurements can be used when variations in the measured factor are small, and may be sufficient to characterize the baseline. Continuous monitoring information can be used to improve or optimize the operation of the equipment over time, thereby improving the performance of the retrofit. This approach provides the greatest accuracy in the calculation of savings.

The intent of Option B is to verify performance periodically or continuously with long-term measurements.

Option C: Whole-Building Verification

Option C is a whole-building verification method. Savings are based on actual energy consumption as measured by the utility meters, usually combined with simple regression modeling to accommodate variables such as weather. Estimated savings will vary during the contract term. 

Option C verification methods determine savings by studying overall energy use in a facility. The whole-building or facility-level metered data are evaluated using techniques that range from simple billing comparison to multivariate regression analysis. Generally, the overall level of savings must be more than 10% to 15% of total metered use for this method to be effective. Analyses usually consider changes in weather, occupancy, load, and operations and adjust the baseline accordingly. Option C cannot verify the performance of individual measures but will verify the total performance of all measures, including interactions between them.

Option D: Whole-Building or Component-Level Verification

Option D is primarily a whole-building method but can be used at the component level. Savings are based on the results of a calibrated computer simulation model. Estimated savings may vary during the contract term if real weather data are used.

Option D uses calibrated computer simulation models of component or whole-building energy consumption to determine energy savings. Linking simulation inputs to baseline and post-installation conditions completes the calibration. Characterizing baseline and post-installation conditions may involve metering performance and operating factors before and after the retrofit. Long-term whole-building energy use data as well as periodic system level performance measurements may be used to calibrate the simulations. More elaborate models generally improve accuracy of savings calculations but increase costs.

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