Verifying the energy savings
Options overview – Option A – Option B – Option C – Option D
Overview of Measurement & Verification Options
When firms invest in energy efficiency, their executives naturally want to know how much they have saved and how long their savings will last. The determination of energy savings is a challenge, and requires both accurate measurement and repeatable methodology, known as a measurement and verification protocol.
The Protocol describes here is called the “International Performance Measurement and Verification Protocol” (IPMVP). The IPMVP is a document which discusses procedures that, when implemented, allow building owners, energy service companies (ESCOs), and financiers of buildings energy efficiency projects to quantify energy conservation measure (ECM) performance and energy savings. The IPMVP provides an overview of current best practice techniques available for verifying savings from both traditionally- and third-party-financed projects. It has been developped by a worlwide network of corresponding members to incorporate international expertise and to develop consensus among professionals from around the world.
Energy savings are determined by comparing energy use associated with a facility, or certain systems within a facility, before and after the Energy Conservation Measure (ECM). The “before” case is called the baseline model. The “after” case is called the post-installation model. Baseline and post-installation models can be constructed using the methods associated with M&V options A, B, C and D described hereafter.
How Savings Are Calculated
Option A: Focuses on physical assessment of equipment changes to ensure the installation is to specification. Key performance factors (e.g., lighting wattage) are determined with spot or short-term measurements and operational factors (e.g., lighting operating hours) are stipulated based on analysis of historical data or spot/short-term measurements. Performance factors and proper operation are measured or checked annually. Engineering calculations using spot or short-term measurements, computer simulations, and/or historical data. Dependent on no. of measurement points. Approx. 1-5% of project construction cost.
Option B: Savings are determined after project completion by short-term or continuous measurements taken throughout the term of the contract at the device or system level. Both performance and operations factors are monitored. Engineering calculations using metered data. Dependent on no. and type of systems measured and the term of analysis/metering. Typically 3-10% of project construction cost.
Option C: After project completion, savings are determined at the “whole-building” or facility level using current year and historical utility meter or sub-meter data. Analysis of utility meter (or sub-meter) data using techniques from simple comparison to multivariate (hourly or monthly) regression analysis. Dependent on no. and complexity of parameters in analysis. Typically 1-10% of project construction cost.
Option D: Savings are determined through simulation of facility components and/or the whole facility. Calibrated energy simulation/modeling; calibrated with hourly or monthly utility billing data and/or end-use metering. Dependent on no. and complexity of systems evaluated. Typically 3-10% of project construction cost.
Only section of the protocol relevant to lighting are reproduced here. For more information, the entire protocol can be downloaded at http://www.ipmvp.org/