Opportunity Class Index

The Opportunity Class Index is a useful tool when making an initial assessment of potential EEMs. The index is formed from a matrix of three key variables – value, complexity and cost – plus any other additional organization-specific variables. Each EEM can be assessed against these variables, assigned to a category and then compared against alternative EEMs.

Value Complexity Cost

Value refers to the financial impact of an EEM, realized in terms of the energy reduction or ROI it achieves.

Value can also apply to how long an EEM is likely to be effective. For example, a change in a control variable in a BMS may apply for 1 year, changing a constant speed chiller to a variable speed may last for 15 years, and installing low emissivity, high efficiency glass would have an expected lifetime of 30 years. Some non-tangible factors, such as improved working conditions or enhanced brand recognition, can be included as well. The actual value will need to be established on a case-by-case basis depending on the EEM itself and the state of the building prior to implementing it.

It is highly recommended that ongoing and end of life costs are considered in addition to potential impacts on other systems as part of an LCCA (Life Cycle Costing Analysis) or similar analysis.

Complexity refers to the amount of technical expertise required to implement an EEM, whether the skills are available in-house and what the impact of implementation will be on end users/employees in the building.

This variable should include some representation of risk, dealing with unknown values and unpredictable repercussions (e.g. interruption to operations) of highly complex solutions that decrease the favorability of the EEM in question.

Cost refers to the total cost for implementing an EEM. This should include both the upfront capital cost of procuring and installing the EEM, and ongoing operational and maintenance costs it requires over time.

Next, categories should be assigned to each variable for each EEM. These need not be any more complex than ‘Low’, ‘Medium’ and ‘High’, and could be assigned using the following suggested cut-off points. In practice, the allocation will inevitably be, to a certain extent, subjective and will vary between organizations to suit their specific circumstance.

Category Low Medium High

< 10 % Energy Savings
ROI > 5 years

10 % < Energy Savings <25 %
5 Years < ROI < 3 Years

Energy Savings > 25 %
3 years < ROI


Internal Team can handle
Low Impact to Business/Staff

Outsource to External Team
Some Impact to Business/Staff

Specialized External Team
High Impact to Business/Staff


Absorbed by OPEX
Less than $ 100 K

Partially OPEX, Need New CAPEX
$ 100 K < Cost < $ 500 K

$ 500 K < Cost

For EEMs where the cost and complexity is ‘Low’ or ‘Medium’, a simple spreadsheet can used with a Net Present Value (NPV) Return on Investment (ROI) or similar calculation to estimate value. Executive management level approval for such projects may not be needed, with a final decision taken by the energy manager in consultation with the energy team.

For higher cost and complexity EEMs it is likely that a more rigorous analysis of value is required, particularly where substantial resources are requested meaning formal support and approval is needed from executive management. An ideal EEM will be high value, low complexity and low cost (as well as being a good fit into the organizational and building level energy efficiency strategies). To help highlight those EEMs that most closely approach this ‘ideal’ case, an EEM matrix can be extended to include an Opportunity Class Index (OCI) column that provides an overall rating of each EEM and can be ranked to allow identification of the EEMs that show the highest potential

Value Complexity Cost Opportunity Class Value Complexity Cost Opportunity Class
High High High C Medium Medium Medium C
High Medium High C Medium Low Medium C
High Low High C Medium High Low B
High High Medium B Medium Medium Low B
High Medium Medium B Medium Low Low B
High Low Medium A Low High High D
High High Low B Low Medium High D
High Medium Low A Low Low High D
High Low Low A Low High Medium D
Medium High High C Low Medium Medium D
Medium Medium High C Low Low Medium D
Medium Low High C Low High Low D
High High Medium C Low Medium Low D

The above example uses an A to D classification for the Opportunity Class Index:

  • Class A is an excellent contender for implementation
  • Class B is also a good candidate but requires further investigation
  • Class C requires more due diligence.
  • Class D is not appropriate at this stage

It should be recognized that this simple approach is best suited to assessing the potential of each EEM independently. A more detailed approach will be required if the combined potential of groupings of two or more EEMs is to be assessed. Once a ‘shortlisting’ exercise has been completed, the shortlisted EEMs need to be further analyzed according to the business case for each. In the matrix above, for example, all EEMs with Opportunity Class A and B could be shortlisted for further investigation, particularly for those EEMs with significant cost or complexity or where approval will be required by senior management, in order to evaluate the costs and associated benefits. Detailed investigation may include sub-metering or real-time metering to a sufficient level of detail to understand the energy use of major systems and items of equipment.