So, What is a Compatible Unit?

Posted by Richard Pike on June 5, 2018

Compatible Units

At a High Level

Compatible Units (CUs alternately referred to as Estimating Units, Assemblies, Kits, Standards, etc.)  have been used in the electric, gas, and telecom utility industry (primarily in Distribution) for well over 50 years. 

In the simplest form, a CU is comprised of Labor, Material and FERC accounting, but can include extended information related to workgroups, vehicles/equipment/tools, etc. required to perform a unit of work.

Compatible Units Defined

A Compatible Unit (CU) is a template used by utility companies to estimate routine, repetitive and primarily capital work such as line construction. (CUs are often used in other industries as well; such as auto repair.) 

For example:  If you contacted an auto repair service to replace a water pump on your 2016 Ford F-150, they could quickly provide you an “estimate” from previously defined estimates of labor and parts and feel confident in providing the quote. The quote would be the same for any customer with the same request providing a “standard” estimate.

compatible units ibm maximo

A CU is a standardized assembly unit defined for general use by utility designers. Each CU represents a “standard” in that it is based on the utility’s current construction practice and represents the same components for every use (usually Labor, Material, and Accounting).  A CU is also an “assembly unit” in that while each CU is comprised of multiple components, it can be used as a building block, combined with other CU’s, for a higher-level or Macro CU. 

compatible units ibm maximo CU ibm maximo

Figure 1 Example CU Structure


Using Compatible Units

An unlimited number of labor and material requirements may be assigned to the CU. Each labor requirement or component (crew or craft) assigned to the CU is associated with standard labor and vehicle/equipment hours to install, remove or transfer structures. Hours are assigned to the CU via the values of one or more of the labor components.

compatible units ibm maximo CU ibm maximo

Figure 2 CU Labor Options

An unlimited number of material items may be assigned to the CU to include stock, exempt (truck or shelf stock), and obsolete (removal only CU) materials. The material items are selected from the master list of material items.

CUs are the building blocks representing estimates (simple and complex) and can have specific attributes. These attributes designate the features of that specific CU (e.g., pole size and wood type such as CCA). One of the most important attributes that CUs carry is accounting information, which is used to assign the labor dollars to the correct FERC asset account.

CU’s are usually combined utilizing the “Point and Span” estimating approach, which involves placing CU’s at Point locations and linear CU’s between points with specified length values.

compatible units ibm maximo CU IBM Maximo

Figure 3 Point and Span Model

This approach facilitates the estimating process in a way that logically groups labor and material.  Estimating applications, such as Maximo CUE, provide mechanisms that convert the point and span estimates into groups of work activities or “Tasks,” consolidating like labor components and materials to facilitate the scheduling and execution of the work.

Let’s take a simple example of using Compatible Units to get a better understanding of how the Labor, Materials, and associated costs are estimated.

Compatible Unit(s) example:

Let’s say we want to develop Compatible Unit(s) to estimate installing an electric utility 45’ pole (0-5 degrees) with a 10’ fiberglass cross-arm, framed for three-phase 35KV with a secondary neutral.

compatible units ibm maximo CU IBM Maximo

Figure 4 Engineering Standard

While we could develop one CU for the entire installation, creating CU’s for component installations allows for maintaining and modifying the construction as conditions change.  For that reason, we will create CU’s for appropriate elements, the pole, cross-arm, insulators, and the neutral.

Let’s start with a CU for installing the Pole.  The pole we will install is a 45’ class 3 CCA treated. For labor, we’ll assume that the pole will be framed on the ground (de-energized) and require 15 minutes of a 3-man line crew.

Compatible Units IBM Maximo CU IBM Maximo

Now let’s develop a CU to install the cross-arm. The cross-arm will be a 10’ fiberglass with a pre-mounted bracket. We will assume that this is installed on the ground (de-energized) and require 5 minutes.

Compatible Units IBM Maximo CU IBM Maximo

Next, let’s develop a CU to install the insulators. Each insulator will be porcelain, rated for 35KV installed on the cross-arm. We will assume that this is installed on the ground (de-energized) and require 2 minutes.

Compatible Units IBM Maximo CU IBM Maximo

Finally, let’s develop a CU to install the insulator for the neutral. This will not include the tie wire as that will depend on the conductor size. As before, this will be installed on the ground (de-energized) and require two minutes.

Compatible Units IBM Maximo CU IBM Maximo

Figure 5 Open Wire Neutral

Compatible Units IBM Maximo CU IBM Maximo

 With these four CU’s we can now estimate the pole installation without having to detail the individual labor and materials components required.

Compatible Units IBM Maximo CU IBM Maximo

In each case the estimated Crew Hours and Bill of Materials. Given a relationship to current crew and material costs, an overall cost estimate can be ascertained as well.

We could also have built a Macro CU or parent CU including the other CU’s as children and in that way, only need one CU to estimate the pole installation.

Compatible Units IBM Maximo CU IBM Maximo

As before, the estimated Crew Hours and Bill of Materials using the Macro CU will be the same as using the individual CU’s producing the same cost estimate.


Compatible units are templates used for simplifying and standardizing the estimation process. They can be combined in a hierarchy to simplify complex estimating.

Some of the key business benefits of CUs for an organization are listed below:

  • Enforcement of Construction and Maintenance Standards
  • Create work orders with consolidated labor and material requirement lists from the standard design elements
  • Seamless integration of design, estimation, mapping, material management and accounting processes
  • Speedy design and accuracy in job estimation
  • Generate estimates with respect to current client contract agreements
  • Helps identify the difference of design to actual costs
  • Integrates with the work order life cycle process
  • Compliance with the reporting requirements of the Public service commission and other regulatory agencies
  • Reduction in Inventory costs
  • Reduction in wasted field trips due to missing material or tools (CU readily provides the list of all the required tools and materials)

Next time we’ll talk about the CU’s and FERC Accounting.



Topics: IBM Maximo, compatible unit, FERC

Written by Richard Pike

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