Barndominium Electrical Service Size: How Many Amps Do You Need?

This barndominium electrical service size calculator is for Tyler and East Texas owners who are choosing between a 100, 150, 200 or 400 amp service, or who have an electrical quote and want to know if the size is in the right range. It gives a planning figure in amps, with no prices. Who connects the wire and what the utility decides is in our electric service guide.

En español: calculadora de tamaño del servicio eléctrico para barndominium

Example: 2,000 sq ft, 4-ton A/C, 10 kW electric heat, electric range, dryer and water heater, dishwasher and a 1 hp well pump, no EV charger or shop load. The range is 10% below to 10% above the central figure, rounded to 5 A.

How the estimate is worked out

1. Add the general loads.

   Floor area at 3 VA per sq ft, plus 1,500 VA for each of two small-appliance circuits and 1,500 VA for the laundry circuit (4,500 VA together), plus the label ratings of the fixed appliances you ticked and any other fixed loads.

2. Apply the demand step.

   The first 10,000 VA counts in full and the rest at 40%. For the example: 35,040 VA of general load becomes 20,016 VA.

3. Add heating or cooling, whichever is larger.

   Air conditioning counts at 100% of its label. Electric heat strips count at 65% when there are fewer than four separately controlled units. Only the larger is added, because they do not run together. Example: 7,500 VA.

4. Convert to amps.

   Total VA divided by 240 volts. For the example, 27,516 VA is 114.7 A. The shown range is 10% below to 10% above, since typical labels are not your labels, and the service size is the smallest standard size at or above the top of it.

What moves the answer most

Same example (4-ton A/C, 10 kW electric heat, all-electric kitchen and laundry, 1 hp well pump). Only the floor area changes.

Floor area moves the answer less than most people expect, because only 3 VA per sq ft is counted and most of it at 40%. Adding 1,000 sq ft adds about 5 amps.

Now the 2,000 sq ft example, changing one thing at a time:

Service size is not panel size

The code sets a floor of 100 amps for a one-family dwelling service. Beyond that, the choice is yours and the electrician's. Common main breaker sizes run 100, 125, 150, 200 and 400 amps.

The shop and outbuildings are a separate question

• Is the shop on the same meter? If so, its welder, air compressor, heaters and lift need to be added, and they are not covered by the dwelling method. Enter what you know in the optional field above and ask the electrician for the full calculation. See shop planning.
• A second meter or a feeder? A separate shop service or a feeder to a subpanel changes what each part needs. Ask the utility and the building official what they allow.
• Well pump and septic? A rural lot often adds a pump motor and sometimes an aerobic septic compressor. See the septic and well guide.
• Will anything be added later? A second charger, a pool or a bigger shop are easier to plan now than to add later.

Questions to ask the electrician

• Which calculation did you use for the service size? Ask for the worksheet, and whether it was the optional dwelling method or the standard one.
• Which loads did you count? They should match your plans: A/C tonnage, electric heat, range, dryer, water heater, EV charger and well pump.
• Does the quote include the shop? If it does, the size should be well above this tool's dwelling figure. Ask which loads were counted.
• How many spare breaker slots will the panel have? Ask for room to add circuits without a new panel.
• Who pulls the permit and arranges the utility inspection? See the Smith County permit guide.
• Is the contractor licensed? Check the electrician's license number with the Texas Department of Licensing and Regulation (TDLR) before signing.

Next step: get a written quote

This tool estimates size, not the price or the job. We are a referral service, not an electrician or a builder; we connect visitors with independent local providers. Use the form below to ask independent barndominium builders near Tyler for a written quote that names the service size and the loads it was based on, and read how to choose a barndominium builder first. To compare quotes side by side, use the bid comparison calculator, or see every line in the budget guide.

Sources

• Single family dwelling calculation, optional method, Jade Learning: the NEC 220.82 steps (3 VA per sq ft, small-appliance and laundry circuits, first 10 kVA at 100% and the rest at 40%). Its worked example uses the 2014 NEC.
• Optional method for dwelling unit service load calculations, Ecuip Engineering: heating at 65% for fewer than four separately controlled units, the larger of heating or cooling, and the 100 amp minimum.
• Electricians compliance guide, Texas Department of Licensing and Regulation: Texas adopts the National Electrical Code by edition, and city permit rules can add to it.
• The typical nameplate values for the A/C, appliances and chargers, and the 10% range, are our planning assumptions, not published values. Well pump currents are the motor full-load figures at 230 volts from the NEC motor tables.