EEI Tests Explained: Which Battery Will You Sit?

If a US electric utility has invited you to a pre-employment test, the battery you sit is decided by the job you applied for, not by the company. The Edison Electric Institute publishes a catalog of nine test batteries, each tied to a family of jobs: line work and other skilled trades go to CAST, power plant operators to POSS, plant maintenance trades to MASS, technician roles to TECH, and control-center dispatchers to SO/PD II. Read your job title against that list and you will know what is coming.

What EEI actually is

EEI is the trade association of US investor-owned electric companies. Its testing arm runs a consortium in which member utilities share a common set of employment tests rather than each building their own. That is why the same four-section trade test turns up at a utility in Kentucky and one in Georgia, and why practicing for it is worth doing at all — the content does not change between employers, only the way each employer uses the result.

The tests are built by outside research firms under EEI sponsorship. The CAST battery came out of a consortium project run by Personnel Designs with 34 investor-owned electric companies taking part; POSS came from a 70-company project run by the Personnel Decisions Research Institute; SO/PD II was developed with HumRRO and 17 companies. Those numbers are in the brochures themselves.

The nine batteries, and who sits each

Battery	Full name	Typical jobs, per EEI's catalog
CAST	Construction and Skilled Trades Selection System	Transmission and distribution work, facilities and equipment, meter reader service and repair
POSS	Plant Operator Selection System	Power plant operator, control room operator, nuclear reactor operator
MASS	Plant Maintenance Positions Selection System	Mechanic, machinist, electrician, welder, pipe fitter
TECH	Technician Occupations Selection System	Laboratory, environmental or chemistry technician; distribution planning technician; communications technician; drafter; estimator
SO/PD II	System Operator / Power Dispatching Selection System	System operator, system controller, power dispatcher
MRAB	Meter Reader Aptitude Battery	Meter reading and data recording
CSR	Customer Service Representative battery	Customer service, call and payment center representatives
SASS	Support and Administrative Selection System	Administrative assistant, clerk
CADI	Career Assessment and Diagnostic Instrument	Not a hiring test — a career-planning profile for existing employees

Three things follow from that table. The first is that there is no such thing as a general "EEI aptitude test": that phrase is prep-industry shorthand, and EEI does not use it. The second is that "BCAB" is not a battery in its own right — it is the Basic Competency Assessment Battery inside SASS, which is why some utilities write "SASS – BCAB". The third is that CADI will never appear in a hiring process, so if someone offers to sell you CADI preparation, they have misread the catalog.

Reading your invitation

Utilities are inconsistent about naming. The same battery appears as "SO/PD II", "SO/PD", "SOPD" and "SO/PDII" depending on whose careers page you are reading. Southern California Edison goes further and refers to everything by internal test numbers — POSS is test 5100, MASS is 5105, TECH is 5107, CAST is 5108 and SO/PD II is 5209 — so an invitation that says "Test 5108" is a CAST invitation.

You may also see CAST written as CAST-R. That is the revised version, and the difference is real: CAST-R drops the Mathematical Usage test and adds a 105-item Work Preferences Inventory. Southern Company is the employer most visibly using the CAST-R name, while others still write plain CAST. If your invitation does not say, prepare for both — the three cognitive tests are the same either way, and we cover the difference in our CAST-R guide.

What the batteries have in common

The batteries are deliberately modular, which is good news if you are preparing. The same 44-question, 20-minute Mechanical Concepts test appears in CAST, CAST-R, POSS, MASS and TECH. Reading for Comprehension appears in CAST, CAST-R, POSS, MASS and SO/PD II. Mathematical Usage appears in CAST, POSS, MASS and SO/PD II. Practise those three and you have covered most of the surface area of five different batteries — which is why our Mechanical Concepts demo and Reading demo are the first things we point people at.

Most batteries take about two hours to administer, with the timed portion considerably shorter than that; SO/PD II is the long one at about two and a half hours. Where a brochure states a policy on guessing, it says there is no penalty for a wrong answer, so leaving a question blank gains you nothing.

Where the scores go

Results are reported to the employer, not to you, and the way they are expressed differs by battery: CAST and CAST-R produce an index from 1 to 10, POSS an aptitude index from zero to 15, SO/PD II a verdict of "Recommended" or "Not Recommended". MASS and TECH produce a combined index whose numeric range the brochures do not publish at all.

What no employer publishes is the level at which it hires. EEI's CAST brochure is explicit that "cutoff scores on the CAST battery can be tailored to local company employment needs" — in other words the bar is set company by company, and no figure you read online applies to your employer. How EEI test scores work goes through this properly.

Frequently asked questions

How do I find out which battery I will sit?

Ask the recruiter, and read the invitation email closely — most utilities name the battery, and some quote an internal test number instead. Failing that, match your job title against the catalog table above: trades and line work means CAST, plant operations means POSS, plant maintenance trades means MASS.

Is the test the same at every utility?

The test content is shared across the consortium, so a CAST at one member company covers the same four tests as a CAST at another. What differs is everything around it: how the employer uses the result, how long you wait before a retake, whether a calculator is available, and whether extra company-specific tests are layered on top.

Do I have to sit more than one battery?

Sometimes. Plant applicants are often tested on POSS and MASS together, a combination EEI's POSS brochure says takes about three hours to administer. Many utilities also add tests of their own — Southern Company lists several alongside the EEI batteries — and physical ability testing is near-universal for field roles.

Which battery should I practice if I have not applied yet?

Start with the sections rather than the battery. Mechanical Concepts and Reading appear in almost everything, so time spent there is never wasted whichever job you end up applying for. Our CAST practice and full access both include them.