The following overarching principles should govern any M&V Plan:
Transparency: all input data, baseline calculations, and variable derivation should be made available to all parties and any authorized reviewers.
Reproducibility: given the same source data and a description of the adjustment methodology, any competent practitioner should be able to produce identical or nearly identical results.
Fairness: baseline adjustments should show no meaningful statistical bias toward a positive or negative outcome (however defined, e.g. higher or lower savings).
In general, the methods outlined in ASHRAE Guideline 14 and IPMVP Option C should be followed. Prior to investment decision-making (e.g. as part of contract development and investment due diligence), an M&V Plan for an energy efficiency improvement should be designed to ensure that reliable accounting methods for energy savings are in place.
Standard M&V Method Quantifying the savings reliably from energy conservation projects requires the comparison of baseline and post-installation energy use normalized to reflect the same set of conditions. The standard method is to utilize the original regression-driven baseline model, applying it to post-installation conditions to represent what the baseline energy use would have been in the absence of an energy conservation program in the building (IPMVP Option C).
Savings are determined by comparison to the baseline energy and post-installation energy use, adjusted to the same set of conditions. The approach requires adjustments to baseline energy use as follows:
Routine adjustments: Account for expected changes in energy use
Non-routine adjustments: Account for unexpected changes in energy use not due to installed ECMs.
Routine adjustments typically include those for changes in weather, occupancy, type of space use, equipment, operating hours, service levels (e.g. a new tenant requires colder air), and utility rates.
The equation for an adjustment takes the general form:
EnergyUsageNew = EnergyUsageBaseline X Change in Conditions
For example, an engineer may estimate the impact of a change in occupancy on the overall energy usage in a building. The adjustment factor to be applied may come from a whole building simulation that estimates the impact based upon the existing systems and their ability to modulate to respond to higher or lower occupancy. Alternatively it might be derived from a comparison of actual usage data for periods of lower and higher occupancy.
Alternative M&V Method In certain cases, full annual utility data may not exist, making it impossible to perform M&V under Option C. In such cases (and only in such cases), it may be acceptable to use Option D, Whole Building Simulation.
A third commonly practiced M&V method, Retrofit Isolation, poses difficulties in accounting for the interactive effects that may occur beyond the boundary of the measured (isolated) retrofit. Such interactions may be either positive (increasing building level savings) or negative (decreasing building level savings). Consequently, Retrofit Isolation is not acceptable as a stand-alone M&V methodology under this specification. However, the method is extremely valuable for monitoring and troubleshooting equipment performance. Retrofit isolation can play a role in improving confidence around savings measurement and trouble-shooting performance if savings do not approach projections.