The dwelling load calculation on the Texas journeyman exam, from floor area to amperes

What the calculation produces

The end product is amperes, and everything before the last line is volt-amperes. That final division is where a surprising number of finished calculations fall over, since a candidate who worked eight steps correctly still has to divide by the right voltage.

On a 120/240 volt single phase service the divisor is 240, the voltage between the ungrounded conductors. A dwelling totaling 43,200 volt-amperes lands at 180 amperes. The bank offers 360 amperes for anyone who divided by 120, which is the voltage to the neutral, and 207.7 amperes for anyone reaching for a three phase relationship on a single phase service. Both options exist because both mistakes are common enough to be worth a distractor.

Working in volt-amperes the whole way is deliberate, since it avoids assuming a power factor for equipment nobody has chosen. One bank item puts "multiply by the power factor" in the answer list for that reason. The conversion to amperes is the last thing that happens, and after it nothing else is selected.

The two unit load figures

The 2026 edition split the general lighting figure, and this is the first cycle in which the two numbers differ. A branch circuit count under 120.13 uses 3 volt-amperes per square foot. A feeder and service calculation under 120.41 uses 2. Both sections are scoped to dwelling units, and another occupancy takes its feeder and service lighting load from Table 120.42(A) at its own figures.

Two decisions happen in order, and the bank builds a four option item from them: first the occupancy, then what you are sizing. In the 2023 edition both sections read 3 volt-amperes per square foot, which is why a candidate who learned the subject last year carries one number and meets two.

Which method the item wants

Texas candidates lose marks here for a reason that has everything to do with being good at the job. In the field you reach for the optional method because it is quicker and it is lawful. In the examination room the standard method is the answer unless the item names the other one.

That comes from the candidate information bulletin, which instructs you to leave code exceptions and optional calculation methods alone unless the question specifically directs you to consider them. Our bank carries the same rule as an item in its own right, with "whichever gives the smaller service" among the wrong answers, since no rule anywhere tells you to pick the smaller of two lawful results.

The optional method is genuinely a code method and a genuinely lawful basis for a service, where the dwelling meets its conditions. 120.82 applies to a dwelling unit served by a single set of 120/240 volt or 208Y/120 volt three wire conductors with an ampacity of 100 amperes or greater. A dwelling split across two sets of service conductors falls outside it, and so does one below that ampacity. Check the condition before you start, since the two methods diverge from the first line.

The standard method in order

The standard method runs in separate tracks that meet at the end, and knowing they run in parallel is what stops a load being reduced twice.

1. The lighting group. Floor area at 2 volt-amperes per square foot, plus 1,500 volt-amperes for each two wire small appliance circuit and each two wire laundry circuit installed. Add it all, then apply the demand brackets once to the subtotal.
2. Cooking. The range takes its demand from the cooking appliance table and stays out of the lighting group, since dropping it in there would apply two demand factors to one load.
3. The dryer. 5,000 volt-amperes or the nameplate rating, whichever is larger.
4. Appliances fastened in place. Count them first. Four or more on the same feeder or service, leaving out ranges, dryers, space heating and air conditioning, earns 75 percent under 120.53. Three of them earn nothing, so the fourth appliance can lower a total.
5. Climate. Heating against air conditioning under 120.60, with the larger carried.
6. The total. Add the tracks, divide by 240, and read the amperes.

One bank item asks when the climate choice is made, and the answer is that it happens independently of the lighting brackets, since a climate load never joins that group. The kitchen and laundry allowances are the piece of track one that people most often leave at full value.

Heating against air conditioning

120.60 treats heating and cooling as noncoincident, so the calculation carries the larger and leaves the smaller out. One bank item calls adding them together the most common error on dwelling calculations, and that option appears in every dwelling item mentioning both.

The version that separates candidates puts a blower in the problem. A dwelling has 10,000 volt-amperes of electric space heating, 7,200 of air conditioning and a 600 volt-ampere blower that runs whenever either one operates. The blower runs with the winner, so it belongs in both groups while you compare them: heating with the blower is 10,600 and cooling with it is 7,800. The figure carried is 10,600, and the blower is counted once.

Work a full dwelling and the size of the error shows up. Take a lighting group of 4,785 after demand, a range demand of 8,000, a dryer at 5,000, appliances at 5,100 after their factor, air conditioning at 7,200 and heating at 9,600. Five of those are simply summed and the climate pair produces one figure, giving 32,485 volt-amperes and about 135 amperes. Adding both climate loads gives 165 amperes, and that is a service size chosen for current the dwelling has no way to draw.

What the optional method changes

The two methods reduce different things, so neither is a shortcut to the other. Here is the comparison we would want on one page the night before.

Run the same dwelling both ways and the answer can flip. One that calculates at 135 amperes by the standard method reaches 108 amperes by the optional method. The climate winner changes too, since heating at 9,600 becomes 6,240 at 65 percent with fewer than four separately controlled units, which puts the air conditioning at 7,200 ahead of it. A sparsely equipped dwelling can come out larger under the optional method, since the standard method's lighting cut is steeper.

How the exam tests it

Forty two of our 500 items sit in the load calculation area and the dwelling is the setting for most of them. The published blueprint puts 24 scored items on the journeyman calculations portion across ten subject areas, with services carrying four, branch circuit calculations four and feeders three. Nothing dominates that portion, so a plan aimed only at motors is aimed at the master paper.

The wrong answers are built from named mistakes. In the area item the four options are 2,640, 3,696, 3,960 and 5,544, and each of the last three is one specific slip. In the full dwelling item, 165 amperes comes from adding both climate loads, 125 from dropping the larger heating load and 271 from dividing by 120. None is a random number, and recognizing your own figure in the list is a signal that a step went missing.

The other shape worth knowing is the mixed method. One item puts a 12 kW range into an optional method calculation and offers the cooking table demand as a wrong answer. Borrowing a step from the standard method into the optional one takes two reductions on one load, and the result is defensible under neither.

The floor under a dwelling service

A correct calculation is one input to the service size, with a separate requirement underneath it. 230.79(C) puts the service disconnecting means for a one-family dwelling at 100 amperes, three wire, whatever figure the calculation returns. A small dwelling that lands at 84 amperes still takes a 100 ampere service.

The bank offers "the next standard rating above 84 amperes" as a wrong answer, which is a different question about rounding, and 125 amperes for anyone who raised the floor above what the section sets. Both come from candidates who knew a rule existed and reached for the wrong one.

That section sits in Article 230 while the calculation sits in Article 120, and the exam will ask one after the other. The services page covers the disconnect side, and the feeder page picks the calculated load up where the conductor sizing rules take over, including the 125 percent for continuous loads that the load calculation article leaves to them.

What to do before test day

The calculations portion gives you 110 minutes for 26 items, a little over four minutes each, and a dwelling calculation worked from a blank page takes longer than that at first. Four things shorten it.

• Write the six tracks down and work three dwellings from that list, so the order arrives on its own. The worked arithmetic on each step, with the section beside it, is what the free question sets go through.
• Tab 120.41, 120.52, 120.53, 120.60 and 120.82 together. They are a few pages apart in the 2026 edition and they are the whole of a dwelling item.
• Say the qualifying condition on 120.82 until it is automatic, since it decides whether the optional method is available to the dwelling in front of you.
• Read the stem for the word optional before you write anything. Without it, the standard method is what the bulletin asks you for.

The licensing side has its own clock. Examination results stay valid for the license term plus three years under 16 TAC 60.56, four years for an electrician license, while the application on file gives you one year to finish everything. The application page sets out both, and they reward passing the calculations portion early.

Questions people ask

How many volt-amperes per square foot is a dwelling service calculation?

Two, under 120.41 in the 2026 edition, for the feeder and service general lighting load of a dwelling unit. The branch circuit figure at 120.13 stayed at three, so the two sections now carry different numbers for the first time. Both are scoped to dwelling units, and other occupancies take their feeder and service lighting load from a separate table at their own values. A candidate who studied from 2023 material carries a single figure of three and will oversize the general lighting portion of a service calculation by half if they use it here.

Which areas of a dwelling are left out of the floor area?

120.41 measures from the outside dimensions of the dwelling and excludes open porches, garages, and unused or unfinished spaces that are not adaptable for future living space. So an attached unfinished garage of 22 feet by 24 feet adds nothing, while a basement that could be finished as living space does count. The exclusion turns on what the space could become, which is why the wording asks whether the area is adaptable. Items usually give you the garage dimensions to see whether you will use them.

Can you use the optional method on the Texas exam?

Only where the item tells you to. The candidate information bulletin instructs candidates to leave code exceptions and optional calculation methods out of their answers unless the question specifically directs otherwise, so the standard method is the default in that room. On the job the optional method is a lawful basis for the service where the dwelling qualifies under 120.82, meaning a single set of 120/240 volt or 208Y/120 volt three wire conductors rated 100 amperes or greater. Working electricians lose marks here because the field habit is the faster method.

How are electric heat and air conditioning handled in a dwelling calculation?

120.60 treats them as noncoincident, so the calculation carries the larger of the two and leaves the smaller out. Equipment that runs with either one, such as an air handler blower, belongs in both groups while you compare them and is then counted once with the winner. Adding the two together is called the most common error on dwelling calculations in our bank, and the resulting figure is always in the answer list. Under the optional method the comparison changes, since heating enters at a reduced percentage while air conditioning enters at 100 percent.

What is the smallest service a one-family dwelling can have?

100 amperes, three wire, under 230.79(C), whatever the load calculation produces. That floor sits in Article 230 while the calculation sits in Article 120, so it applies on top of whatever the arithmetic returns. A calculation that lands at 84 amperes is a correct calculation and the service is still 100 amperes. The bank offers the calculated load itself as a wrong answer, along with 125 amperes for candidates who remember a floor exists and raise it above the figure the section actually sets.

How long do you get per calculation item on the Texas journeyman exam?

The calculations portion runs 110 minutes for 26 items, of which 24 are scored, which works out at a little over four minutes each on the paper in front of you. A full dwelling calculation worked from nothing takes longer than that until the order is automatic, which is the argument for drilling the sequence itself. That portion is scored on its own at 70 percent, and TDLR reported a 20.6 percent pass rate on it for fiscal year 2025, the lowest of the four portions the department publishes.