- Why the 10 Domains Drive Everything on Exam Day
- How TDLR Weights the 10 Content Areas
- Domain 1: Definitions, Calculations, Theory, and Plans
- Domain 2: Electrical Services, Service Equipment, and Separately Derived Systems
- Domain 3: Electrical Feeders
- Domain 4: Branch Circuit Calculations and Conductors
- Domain 5: Electrical Wiring Methods and Electrical Materials
- Domain 6: Electrical Equipment and Devices
- Domains 7 & 8: Motors, Generators, Control Devices, and Disconnects
- Domain 9: Special Occupancies, Equipment, and Conditions
- Domain 10: Renewable Energy Technologies
- Working With Your NEC 2026 on Test Day
- A Domain-Based Study Order That Matches the Weighting
- FAQ
- The TX-RW exam has 80 scored questions spread across 10 domains, weighted from 2 to 16 questions each.
- Domain 2 (Electrical Services, Service Equipment, and Separately Derived Systems) is the heaviest at 16 questions.
- Branch Circuit Calculations and Conductors (14) and Electrical Equipment and Devices (12) are the next-largest content areas.
- Four domains - Motors and Generators, Control Devices and Disconnects, and Renewable Energy - carry only 2 questions each.
Why the 10 Domains Drive Everything on Exam Day
The Texas Residential Wireman Electrician License Exam (TX-RW), administered by PSI Services LLC on behalf of the Texas Department of Licensing and Regulation (TDLR), is not a generic electrical trivia test. It is built from a fixed content outline: 10 named domains, each assigned a specific number of scored questions. Of the 85 total questions you will see, 80 are scored and 5 are unscored pretest items you cannot identify, spread across 240 scored minutes plus 20 additional minutes for the unscored set - four hours and 20 minutes total. A 70% passing score means you need roughly 56 of the 80 scored items correct, and every one of those items maps back to one of the 10 domains below.
Understanding the domain breakdown is the single most efficient way to allocate study time. If you're still deciding how to prepare in general, the TX-RW Study Guide 2026 covers overall strategy, while this article focuses specifically on what lives inside each of the 10 content areas.
How TDLR Weights the 10 Content Areas
The official scored-item allocation, in domain order, is 8, 16, 7, 14, 10, 12, 2, 2, 7, 2 - totaling 80. That means three domains alone (Domain 2, Domain 4, and Domain 6) account for 42 of your 80 scored questions, over half the exam. If you're weighing how tough this exam feels compared to other licensing paths, the domain concentration is a big part of the answer discussed in How Hard Is the TX-RW Exam? Complete Difficulty Guide 2026.
| Domain | Content Area | Scored Questions |
|---|---|---|
| 1 | Definitions, Calculations, Theory, and Plans | 8 |
| 2 | Electrical Services, Service Equipment, and Separately Derived Systems | 16 |
| 3 | Electrical Feeders | 7 |
| 4 | Branch Circuit Calculations and Conductors | 14 |
| 5 | Electrical Wiring Methods and Electrical Materials | 10 |
| 6 | Electrical Equipment and Devices | 12 |
| 7 | Motors and Generators | 2 |
| 8 | Electrical Control Devices and Disconnecting Means | 2 |
| 9 | Special Occupancies, Equipment, and Conditions | 7 |
| 10 | Renewable Energy Technologies | 2 |
For a deeper look at what a 70% passing score means against this specific weighting, see TX-RW Passing Score 2026: Exactly What You Need to Pass.
Domain 1: Definitions, Calculations, Theory, and Plans
Definitions, Calculations, Theory, and Plans - 8 Questions
This domain establishes the vocabulary and math foundation used everywhere else on the exam. Expect questions on NEC Article 100 definitions, basic Ohm's law and power calculations, and reading residential electrical plans or riser diagrams.
- Interpreting symbols and load schedules on single-family and multifamily plan sets
- Applying standard calculation methods with copper conductors unless a question explicitly directs otherwise
- Recognizing terminology that recurs across service, feeder, and branch-circuit questions later in the exam
Because this domain underpins later calculation-heavy sections, weak fundamentals here tend to cost points in Domains 2 and 4 as well.
Domain 2: Electrical Services, Service Equipment, and Separately Derived Systems
Electrical Services, Service Equipment, and Separately Derived Systems - 16 Questions
This is the largest domain on the entire exam, nearly a fifth of all scored questions. It covers service entrance sizing, grounding and bonding of service equipment, and separately derived systems such as generators or transformer-fed subsystems.
- Service conductor and disconnect sizing for single-family and multifamily dwellings up to four stories
- Grounding electrode conductor sizing and bonding jumper requirements
- Separately derived system grounding rules and where a new grounding electrode is required
Key Takeaway
Because Domain 2 is worth twice as much as most other domains, spend proportionally more practice time on service-entrance calculations and grounding/bonding scenarios than on any single other topic.
Domain 3: Electrical Feeders
Electrical Feeders - 7 Questions
Feeder questions test your ability to size conductors and overcurrent protection between the service and downstream panels or subpanels in residential structures.
- Feeder conductor ampacity and derating for conditions such as conduit fill or ambient temperature
- Feeder overcurrent protection sizing and coordination with panel schedules
- Voltage drop considerations when a question directs you to apply them
Domain 4: Branch Circuit Calculations and Conductors
Branch Circuit Calculations and Conductors - 14 Questions
The second-largest domain, this section focuses on sizing individual branch circuits, general lighting and appliance loads, and conductor selection for residential wiring.
- Branch circuit load calculations for kitchens, laundry, and small-appliance circuits
- Conductor ampacity tables and correction/adjustment factors
- Multiwire branch circuits and required disconnecting means
Together, Domains 2 and 4 make up 30 of the 80 scored questions - more than a third of the exam. Candidates researching overall exam difficulty in How Hard Is the TX-RW Exam? consistently flag calculation-heavy domains like these as the biggest time pressure on test day.
Domain 5: Electrical Wiring Methods and Electrical Materials
Electrical Wiring Methods and Electrical Materials - 10 Questions
This domain covers the physical installation rules for cables, raceways, and boxes typically found in residential construction.
- Nonmetallic-sheathed cable (NM), armored cable, and conduit installation rules
- Box and enclosure fill calculations
- Support, securing, and protection requirements for wiring methods run through framing
Domain 6: Electrical Equipment and Devices
Electrical Equipment and Devices - 12 Questions
The third-largest domain tests your knowledge of receptacles, switches, luminaires, and other equipment installed in dwelling units.
- GFCI and AFCI protection requirements by room and circuit type
- Receptacle spacing and placement rules for kitchens, bathrooms, and outdoor areas
- Luminaire and ceiling fan support and outlet box requirements
Domains 7 & 8: Motors, Generators, Control Devices, and Disconnects
These two domains are the lightest on the exam, each worth only 2 scored questions, but they still require accurate recall since every point matters against the 70% passing threshold.
Domain 7: Motors and Generators - 2 Questions
Expect a small number of questions on residential-scale motor circuits (such as HVAC or well pump motors) and portable or standby generator connections.
- Motor overload and branch-circuit protection basics
- Generator disconnecting means and interconnection rules
Domain 8: Electrical Control Devices and Disconnecting Means - 2 Questions
This domain covers switches, contactors, and required disconnects for equipment such as HVAC condensers or water heaters.
- Disconnect location and accessibility requirements
- Control device ratings appropriate to residential equipment
Because these domains carry so few points, most candidates cover them quickly during review rather than dedicating full study sessions - a pacing decision detailed further in the TX-RW Study Guide 2026.
Domain 9: Special Occupancies, Equipment, and Conditions
Special Occupancies, Equipment, and Conditions - 7 Questions
This domain addresses locations and equipment that carry extra NEC requirements beyond typical living spaces.
- Wet, damp, and hazardous location wiring adjustments relevant to residential settings
- Swimming pool, spa, and outdoor equipment bonding and clearance rules
- Garage, basement, and accessory structure wiring conditions
Domain 10: Renewable Energy Technologies
Renewable Energy Technologies - 2 Questions
The smallest domain on the exam, covering basic residential renewable energy installations such as solar photovoltaic systems.
- PV system disconnects and labeling requirements
- Interconnection basics for residential renewable systems
Even at only 2 questions, don't skip this domain entirely - with a 70% passing threshold, every scored question contributes to the margin discussed in TX-RW Passing Score 2026.
Working With Your NEC 2026 on Test Day
All 10 domains are graded against the current code edition referenced in the PSI bulletin, and the bulletin updated July 9, 2026 shifts examination references to NEC 2026, effective September 1, 2026. That means every domain above - from service sizing in Domain 2 to PV disconnects in Domain 10 - will be tested against the newer code text once that date passes.
- Bring a softbound NEC; you may add notes, highlighting, or underlining completed before the exam.
- Permanent index tabs must be manufactured or provided by the NEC publisher - no homemade, third-party, or movable tabs, no added sheets, no NEC Handbook, and no loose-leaf, spiral-bound, or ring-bound books.
- You cannot mark the book during the exam itself; PSI issues an electronic notepad for calculations and notes.
- Unless a question explicitly directs otherwise, use copper conductors and standard calculation methods - don't assume exceptions or optional methods apply.
A Domain-Based Study Order That Matches the Weighting
Rather than studying the 10 domains in the order TDLR lists them, most candidates get more value from tackling the heaviest domains first while their study time is freshest, then circling back to the lighter domains for quick review passes.
Domains 2 and 4
- Service and separately derived system sizing (16 questions)
- Branch circuit calculations and conductor sizing (14 questions)
Domain 6 and Domain 5
- Equipment and device rules - GFCI/AFCI, receptacle placement (12 questions)
- Wiring methods and materials - cable, conduit, box fill (10 questions)
Domain 1, Domain 3, and Domain 9
- Definitions, calculations, and plan reading (8 questions)
- Feeder sizing and protection (7 questions)
- Special occupancies and equipment conditions (7 questions)
Domains 7, 8, and 10
- Motors and generators, control devices and disconnects, renewable energy (2 questions each)
- Full-length practice runs using open-book NEC lookups under timed conditions
This sequencing mirrors the weighting shown in the table above, so the domains worth the most points get the most repetition. For a condensed reference once you've studied each domain, the TX-RW Cheat Sheet 2026 summarizes must-know facts by topic.
Who These Domains Matter To
The TX-RW license scope covers single-family and multifamily dwellings not exceeding four stories, which is exactly why the domain weighting leans so heavily toward services, branch circuits, and equipment common in residential construction rather than industrial or commercial motor control. Qualifying requires 4,000 documented on-the-job hours supervised by a Texas-licensed Master Electrician or Residential Wireman, or completion of a TDLR-approved career and technology education program, with separate signed experience verification from each supervisor. If you're still confirming you meet the prerequisites before registering, review TX-RW Requirements 2026: Eligibility, Prerequisites & How to Qualify.
Once your TDLR application is approved and you're within your one-year eligibility window, you can schedule your attempt for $64 per exam attempt (plus the separate $20 initial license application fee) and, if needed, retake it during that same eligibility period. Scheduling logistics and deadlines are covered in TX-RW Exam Dates 2026: Testing Windows, Deadlines & Scheduling, and the full cost picture - including the $20 annual renewal with four CE hours in NEC, Texas electrician law, and NFPA 70E - is broken down in TX-RW Certification Cost 2026: Complete Pricing Breakdown.
You can build familiarity with each domain's question style using structured practice questions on our TX-RW practice test platform before committing to a scheduled exam date.
Frequently Asked Questions
Domain 2, Electrical Services, Service Equipment, and Separately Derived Systems, carries 16 of the 80 scored questions - the largest single domain on the exam.
No domain should be skipped entirely, but Motors and Generators, Electrical Control Devices and Disconnecting Means, and Renewable Energy Technologies each carry only 2 scored questions, so they warrant lighter review time than Domains 2, 4, and 6.
The 10 domain names and question counts stay the same, but the underlying code citations within each domain shift to NEC 2026 once the September 1, 2026 effective date from the July 9, 2026 PSI bulletin update takes hold.
Yes, the exam is open book across all 10 domains. You may bring a softbound NEC with notes and highlighting completed beforehand, but only permanent, publisher-made index tabs are allowed - no homemade tabs, added sheets, or the NEC Handbook.
You need roughly 70% of the 80 scored questions correct overall; the domain weighting tells you where those points are concentrated so you can prioritize study time toward Domains 2, 4, and 6 first.