In Texas, an outage can begin during a triple-digit afternoon, a severe thunderstorm, or a hard winter freeze. When the air conditioner stops and the refrigerator begins warming, a standby generator can make the disruption far easier to manage.



Choosing the right whole-home generator size is not as simple as matching a unit to your square footage. The generator must support the appliances you plan to use, motor-starting surges, your fuel source, and your electrical system. In North Central Texas, ERCOT reported a preliminary peak demand record of 91,089 megawatts on July 22, 2026.

Why Whole-Home Generator Size Matters

Generator sizing follows a “Goldilocks” rule: not too small and not unnecessarily large.



An undersized generator may bog down when several loads start together. Breakers can trip, voltage may drop, overload alarms may appear, or the unit may shut down. Repeated overloading also stresses the equipment.

An oversized unit can add avoidable equipment, installation, and fuel costs. The goal is enough capacity for planned loads plus sensible reserve.

Understanding Running Watts vs. Starting Watts

Generator output is measured in kilowatts, or kW. One kilowatt equals 1,000 watts.

Running watts are the power an appliance uses while operating. Starting watts, or surge watts, are the brief burst needed to start a motor or compressor.



This matters most with central air conditioning. Generac notes that motor-driven equipment such as AC systems may need three to four times its running wattage at startup. A generator can therefore appear large enough on paper but still struggle when the compressor starts.

A standby generator for a Texas home must be sized with this cooling demand in mind. Other major loads include electric water heaters, ranges, dryers, heat-pump backup strips, well pumps, pool equipment, and EV chargers.

A generator wattage calculator can provide a rough estimate, but final sizing should use actual equipment data and account for loads that may run together.

Essential Circuits vs. Whole-House Coverage

Before asking, “What size generator do I need?” decide what you expect to use during an outage.

An essential-circuit system keeps selected necessities operating, such as refrigeration, basic lighting, outlets, internet equipment, security devices, and possibly one HVAC system when capacity allows.

A whole-house system supports most or all household circuits. That does not always mean every large appliance can run at once. Load-management controls can temporarily delay a pool pump, dryer, or other lower-priority load while the air conditioner starts.

This can deliver comfortable backup without oversizing.

Average Generator Sizes for Texas Homes

These ranges are useful for planning, but they are not a substitute for a professional load calculation.

Generator Size and General Planning Range

10–14 kW

Essential circuits, refrigeration, lights, outlets, and possibly a managed HVAC load

18–24 kW

Many average homes with one central AC system and selected 240-volt appliances

26–30+ kW

Larger homes, multiple AC systems, pumps, or several high-demand electric appliances

Square footage alone can mislead. A larger home with gas heat, cooking, and water heating may require less capacity than a smaller all-electric home.

Fuel matters, too. One current 24 kW standby model is rated for 24 kW on propane but 22.5 kW on natural gas. Always use the rating for the fuel that will serve the home.

A project may also require panel or electrical service changes.

Why Professional Generator Sizing Is Critical

Whole-house generator installation involves more than placing a unit outdoors.



A licensed electrical contractor should evaluate the electrical service, panel, AC startup load, fuel supply, installation site, automatic transfer switch, grounding, bonding, and load-management controls. The transfer switch safely changes the home from utility power to generator power and prevents the two sources from being connected together.

Texas requires non-exempt residential backup-system electrical work to follow the National Electrical Code and be completed through a licensed electrical contractor using licensed electricians. A Texas electrical contractor must employ a licensed master electrician of record.

For local homeowners, choosing a Weatherford electrician familiar with North Texas homes, utilities, and climate conditions helps remove guesswork from the process. Professional sizing helps ensure reliable performance during a real outage.

Signs It Is Time to Call Purefoy Electric

Request a professional load calculation when your home has multiple AC units, electric heat, a well or pool pump, an EV charger, an older panel, or several large 240-volt appliances. Get help if you are unsure which circuits need priority.



It is also smart to schedule a consultation when:

• You want central air conditioning during an outage.
• Your home has an all-electric water heater, range, or heating system.
• You are deciding between essential-circuit and whole-house coverage.
• An online calculator recommends several different generator sizes.
• You may need panel or service upgrades before installation.

Flexible payment options may be available through Purefoy Electric’s financing options.

Choose Backup Power With Confidence

The correct whole-home generator size depends on how your family uses electricity, not just the size of the house.

Since 1999, Purefoy Electric, LLC has served homeowners across Weatherford, Fort Worth, Aledo, Arlington, Granbury, Frisco, Keller, and North Central Texas. Contact the team for a professional consultation, load calculation, and installation before the next heatwave, storm, or freeze.



Purefoy Electric also provides 24/7 electrical service with a commitment to family, faith, and integrity.

Frequently Asked Questions