How to evaluate energy savings

From Electrical Installation Guide

One of the main obstacles facing those interested in devising and implementing energy efficiency projects is the lack of reliable financial data to provide a convincing business case. The higher the investment, the greater the need for credible proof of the proposed advantages. As such, it is very important to have reliable methods for quantifying results when investing in energy efficiency.

IPMVP and EVO procedures

The information provided in this chapter is taken from Volume 1 of the IPMVP guide published by EVO (see

To cater for this need, EVO (Efficiency Evaluation Organization), the body responsible for evaluating performance, has published the IPMVP (International Performance Measurement and Verification Protocol). This guide describes the procedures used when measuring, calculating and documenting the savings achieved as a result of various energy efficiency projects. So far, EVO has published three volumes of the IPMVP, the first of which, “Concepts and Options for Determining Energy and Water Savings”, outlines methods of varying cost and accuracy for establishing total savings made or those made solely in terms of energy efficiency. Schneider Electric uses this document when putting together energy efficiency projects.

IPMVP principles and features

Before implementing the energy efficiency solution, a study based on IPMVP principles should be carried out over a specific period in order to define the relationship which exists between energy use and operating conditions. During this period, reference values are defined by taking direct measurements or by simply studying the energy bills for the site.

After implementation, this reference data is used to estimate the amount of energy, referred to as “adjusted-baseline energy”, which would have been consumed had the solution not been implemented. The energy saved is the difference between this “adjusted-baseline energy” and the energy which was actually measured.

If a verification and measurement plan is put together as part of an IPMVP programme, it needs to be:

  • Accurate
Verification and measurement reports should be as accurate as possible for the budget available. The costs involved in verification and measurement should normally be comparatively low in terms of the anticipated savings.
  • Complete
The study of energy savings should reflect the full impact of the project.
  • Conservative
Where doubts exist in terms of results, verification and measurement procedures should underestimate the savings being considered.
  • Consistent
The energy efficiency report should cover the following factors in a consistent manner:
  • The various types of energy efficiency project
  • The various types of experts involved in each project
  • The various periods involved in each project
  • The energy efficiency projects and the new energy supply projects
  • Relevant
Identifying savings must involve measuring performance parameters which are relevant or less well known, with estimates being made for less critical or more predictable parameters.
  • Transparent
All the measurements involved in the verification and measurement plan must be presented in a clear and detailed manner.

IPMVP options

Four study levels or “options” have been defined in line with the objectives assigned to this energy efficiency approach:

  • Retrofitting isolation systems with measurements of all key parameters = Option A
  • Retrofitting isolation systems with measurements of all parameters = Option B
  • Whole facility = Option C
  • Calibrated simulation = Option D

Figure K34 sets out these options in a table. The algorithm in Figure K35 shows the process of selecting options for a project.

Fig. K34 – Summary of IPMVP options
Option A Option B Option C Option D
Financial objective Retrofit isolation systems: key parameter measurement Retrofit isolation systems: all parameter measurement Whole facility Calibrated simulation
Description Savings are calculated using data from the main performance parameter(s) defining energy consumption for the system involved in the energy efficiency solution. Estimates are used for parameters not chosen for actual measurements. Savings are calculated using actual energy consumption data for the system involved in the energy efficiency solution Savings are established using actual energy consumption data for the facility or a section of it. Data for energy use within the facility as a whole is gathered on an ongoing basis throughout the reporting period. Savings are established by simulating energy consumption for the facility or a section of it. There must be evidence that the simulation procedures are providing an adequate model of the facility’s actual energy performance.
Savings calculation An engineering calculation is performed for the energy consumed during the baseline period and the reporting period based on:
  • Ongoing or short-term measurements of the main performance parameter(s),
  • And estimated values.
Ongoing or short-term measurements of the energy consumed during the baseline period and the reporting period An analysis of data on the energy consumed during the baseline period and the reporting period for the whole facility. Routine adjustments are required, using techniques such as simple comparison or regression analysis. Energy use simulation, calibrated with hourly or monthly utility billing data
When to use option On the one hand, the results obtained using this option are rather equivocal given that some parameters are estimated. Having said this, it is a much less expensive method than Option B. Option B is more expensive than Option A, as all parameters are measured. It is the better option, however, for customers who require a high level of accuracy. For complex energy management programmes affecting many systems within a facility, Option C supports savings and helps to simplify the processes involved. Option D is only used when there is no baseline data available. This may be the case where a site did not have a meter before the solution was implemented or where acquiring baseline data would involve too much time or expense.
Fig. K35 – Process for selecting an IPMVP option for a project

Achieving sustainable performance

Once the energy audits have been completed, the energy saving measures have been implemented and the savings have been quantified, it is essential to follow the procedures below to ensure performance can be sustained over time. Performance tends to deteriorate if there is no continuous improvement cycle in place (see Fig. K36).

Fig. K36 – Ensuring performance is sustainable over time

A continuous improvement cycle will only work if there is an energy monitoring system in place, and this system is used effectively and maintained. The system supports a continuous and proactive analysis of energy use at the site, and informs recommendations for improving the electrical distribution system.

Support services, either on site or at a remote location (accessible via telephone, e-mail, VPN (Virtual Private Network) or any other type of long-distance connection), are often required to ensure optimal performance for this type of system and the best use of the collected data. Thanks to their contribution in terms of experience and availability, these services also complement the operator’s in-house services. The services available may include:

  • Monitoring the performance of measuring devices
  • Updating and adapting software
  • Managing databases (e.g. archives)
  • Continuously adapting the monitoring system in line with changing control requirements.