Calculating and communicating energy savings

The energy savings attributable to a specific project can be described by using the following equation:

Energy savings = (Baseline energy use) ± (Adjustments) - (Post installation energy use)

Where:

  • Baseline energy use is the energy consumed before implementation of the energy conservation initiative
  • Adjustments relate to changes in production, weather, property portfolio, etc.
  • Post installation energy use, sometimes referred to as performance or reporting period, is the energy consumption after the project or program is implemented

Measurement and verification options are broadly divided into two categories, each with specific methods:

M&V option Isolation Whole facility
Scope of M&V Considers specific equipment or systems, independent of the rest of the facility. This may require sub-metering. Considers total energy use from a facility as a whole.
M&V Options 1

Instantaneous or short-term parameter measurement This is based on a combination of measured and estimated factors where significant variations are not expected over time. Measurements are instantaneous (spot) or short-term and are taken at component or system level during both the baseline and post-installation phases. Measurements must include the key performance parameter(s) that define the EEM’s energy use.

Utility data analysis This determines energy savings at a whole building level. It is applied to projects where the individual effects of the EEMs cannot be accurately assessed by measuring before and after energy use by using any of the retrofit isolation methods, or when the impact of the EEM has further knock-on impacts on other systems (e.g. reduced AC use due to lower heat gain from new lighting).

Long-term parameter measurement This is used when significant variations in factors affecting energy consumption are expected over time. This isolates the performance of an EEM and verifies actual achieved energy savings using long-term or permanently installed metering or monitoring systems.

 

Visual analysis of the energy consumption data can act as a focus for energy-saving efforts. It helps determine a starting point for energy savings, the steps needed to achieve them and provides a means for monitoring ongoing progress. An energy dashboard, such as the example below, will give the energy manager and other employees a clear, concise and, in some cases, real-time view of energy use.


The energy dashboard available for NREL’s Research Support Facility building2

Dashboards can be developed with varying degrees of detail depending on who will be viewing them. Some stakeholders may only need to see a high-level overview of energy performance, but the other users will need to see more detailed information about specific equipment or behavioral patterns. One of the benefits of starting with high-level data is that it can show where there are anomalies that need investigating in more detail.

Automated data analysis and tracking software and systems can be used to:

  • Develop quarterly and annual reports that profile energy performance
  • Allow facilities to compare performance with their peers
  • Organize data and benchmark against industry standards
  • Understand the contribution of energy expenditures to operating costs
  • Develop a historical perspective and context for future actions and decisions
  • Establish reference points for measuring and rewarding good performance
  • Identify high-performing facilities for recognition and replicable practices
  • Prioritize poor performing facilities for immediate improvement

References

1 Efficiency Valuation Organization, 2012. International Performance Measurement and Verification Protocol: Concepts and Options for Determining Energy and Water Savings, Volume 1. Available online

2 National Renewable Energy Laboratory, 2013. ‘NREL: A Living Laboratory for Energy Systems Integration’, Continuum Magazine, Issue 4 - NREL Leads Energy Systems Integration. Available online