What Size Generator Do I Need for My Texas Home?

Generator sizing is the single most important decision in a standby generator project — and it's where most mistakes happen. Undersize it and your generator shuts down on the hottest day of the year, exactly when you need it. Oversize it and you've paid for capacity you'll never use, plus higher fuel consumption every time it runs.

Here's how generator sizing actually works, why Texas homes are different, and how to figure out what your home needs.

Running Watts vs. Starting Watts — The Number That Trips People Up

Generator sizing is based on two numbers: running watts and starting watts. Running watts is the power an appliance uses during normal operation. Starting watts is the surge of power needed to start the appliance — motors (like your AC compressor) can require 2 to 3 times their running wattage to start.

This is why undersized generators fail during Texas summers. If your 14 kW generator is already running your AC, refrigerator, and lights, it may not have enough headroom to start the washing machine or a second HVAC zone — and it will shut down trying.

Appliance	Typical Running Watts	Typical Starting Watts
Central AC (3-ton)	3,500	8,000–10,000
Well pump (1 HP)	1,000	2,000–3,000
Refrigerator	200	1,200
Electric water heater	4,500	4,500
Washing machine	1,200	2,300
Lights & outlets (whole home)	1,000–2,000	—

Add up what you want running simultaneously, account for the largest starting surge on top of that, and you have your minimum generator size. That's the math a load calculation formalizes.

Why Texas Homes Need Bigger Generators Than the Guides Say

Most generator sizing guides are written for northern climates where heating is the main concern. In Texas, air conditioning is the dominant electrical load — and AC units have extremely high starting wattages. A generator sized "just right" for a northern home is often undersized for a Texas home running AC in 100°F+ summer heat.

Generator Sizing by Coverage Level

Sizing by Home Size — A Starting Point

Square footage alone doesn't determine generator size — your electrical loads do. But as a starting point for Texas homes:

• Under 1,500 sq ft: 10–16 kW typically covers essentials through full coverage, depending on HVAC size.
• 1,500–2,000 sq ft: A 16–22 kW generator powers essential systems including HVAC, refrigerator, lights, outlets, and a well pump. A 22 kW unit provides comfortable whole-home coverage for most homes this size.
• 2,000–3,500 sq ft: 22 kW is sufficient for most Texas homes in this range with a single HVAC system. It will power your air conditioning, refrigerator, lights, outlets, and most appliances simultaneously.
• 3,500+ sq ft or multiple HVAC systems: 24 kW or larger, often with load management to prioritize circuits.

Do You Need a Panel Upgrade First?

Not always — but often yes. If your home has a 100A panel, upgrading to 200A before installing a generator is strongly recommended. A 22 kW generator feeding power into a 100A panel is like running a fire hose through a garden hose. We assess your panel during the free generator consultation and include panel upgrade recommendations in the quote if needed. Many homeowners combine both projects for maximum efficiency and savings.

Fuel Type Matters Too

Natural gas generators can run indefinitely as long as gas supply is available — the right choice for homes with existing gas service. Propane generators run until the tank is empty; a 500-gallon tank typically provides 5–7 days of continuous power at 50% load. For rural Hill Country properties without natural gas service, propane is the standard. Rural properties should also factor well pumps into sizing — losing power means losing water.