An undersized generator will overload and shut down. An oversized generator wastes fuel and money. Here is exactly how DFW electricians size standby generators — from load calculations to real installation costs by kilowatt rating.
The most expensive mistake you can make when buying a standby generator is guessing the size. An undersized generator will overload during the first summer heat wave, shut itself down, and potentially damage your air conditioner. An oversized generator burns more fuel than necessary, cycles on and off excessively, and costs thousands more upfront for capacity you will never use. At Clements Electric, we perform a formal load calculation on every home before recommending a generator size. Here is exactly how that process works and what size generator your Dallas–Fort Worth home actually needs.
Why Generator Size Matters More Than Brand
Homeowners love to debate Generac vs Kohler vs Cummins. But brand debates are irrelevant if your generator is the wrong size. A properly sized 20kW Generac will outperform an undersized 22kW Kohler every single time. Sizing determines whether your generator runs at 50% load (ideal) or 95% load (stressful and short-lived). It also determines whether you need load-shedding modules, how large your gas line must be, and whether your existing electrical panel can handle the transfer switch integration without additional upgrades.
How to Calculate Your Home's Electrical Load
We use two methods to size generators: the full load method and the essential load method. Here is what each looks like in practice:
Full Load Method
The full load method assumes you want to power everything in your home simultaneously — every AC unit, every light, every appliance, every outlet. We add up the wattage of all your major appliances, add a 25% safety margin for motor starting surge, and select a generator that covers the total. For a typical 2,500 sq ft DFW home with two AC units, this usually lands between 22kW and 26kW.
Essential Load Method
The essential load method is more practical for most budgets. We identify the circuits you absolutely need during an outage: refrigerator, freezer, one AC unit, critical lighting, medical devices, security systems, and internet. We calculate the wattage for those circuits only and size the generator accordingly. This often drops the requirement to 14kW – 18kW, saving thousands on both the generator and the installation.
Common Generator Sizes for DFW Homes
Here are the sizes we install most often and the home profiles they match:
- 10kW – 14kW: Small homes under 1,500 sq ft, condos, townhomes, or essential-circuit-only setups. Powers refrigerator, lights, internet, and one small AC unit with load management.
- 16kW – 20kW: Medium homes 1,500 – 2,500 sq ft with one central AC. Full-home coverage possible if you have gas heat, gas water heater, and gas cooktop.
- 22kW – 26kW: Large homes 2,500 – 4,000 sq ft with two AC units. This is the sweet spot for most DFW suburbs. Can handle full-home loads with smart load management.
- 30kW – 48kW: Estate homes 4,000+ sq ft with three AC units, pools, guest houses, and high-demand workshops. Requires liquid-cooled unit and upgraded gas service.
- 50kW+: Commercial properties, multi-family buildings, and estates with multiple structures. Requires site-specific engineering and gas line upgrades.
What Happens If Your Generator Is Undersized?
An undersized generator tries to supply more power than it can generate. The voltage drops. Motors on your AC compressor and refrigerator strain, overheat, and burn out. The generator's overload protection shuts it down repeatedly. In extreme cases, the generator itself is damaged. We see this most often when homeowners buy a 14kW unit for a 3,500 sq ft home with two AC units because the online calculator told them it was enough. Online calculators do not account for Texas heat, multi-stage compressors, or well pumps.
What Happens If Your Generator Is Oversized?
Oversizing is less dangerous but still wasteful. A generator running at 20% load builds carbon deposits in the engine, wastes fuel, and experiences wet stacking — a condition where unburned fuel accumulates in the exhaust. It also costs more upfront, requires a larger gas meter and regulator, and takes up more space in your yard. The ideal load range is 50-80% of the generator's rated capacity.
Installation Costs by Generator Size in Texas (2025)
These are complete installed prices including the generator, automatic transfer switch, gas line coordination, electrical connection, permitting, and startup testing:
- 10kW – 14kW air-cooled: $4,500 – $7,000 installed
- 16kW – 20kW air-cooled: $5,500 – $8,500 installed
- 22kW – 26kW air-cooled: $6,500 – $11,000 installed
- 30kW – 38kW liquid-cooled: $12,000 – $18,000 installed
- 45kW – 60kW liquid-cooled: $18,000 – $28,000 installed
The price variation depends on your home's distance from the gas meter, whether your electrical panel needs upgrading, and whether concrete pad preparation is needed. Homes in newer developments often have gas meters within 10 feet of the desired generator location, which keeps costs lower. Older homes in Dallas or Fort Worth may require 30+ feet of gas line trenching.
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Schedule a Free Generator Sizing ConsultationFrequently Asked Questions
Yes, if your home is under 3,500 sq ft with two AC units or less. A 22kW generator produces enough power for most essential loads plus one AC unit simultaneously. With a smart load management module, it can prioritize circuits and run both AC units on a staggered basis — one starts, then the other. For homes with pool pumps, electric water heaters, or workshops, you may need 26kW or larger.
Yes. Larger generators consume more fuel per hour. A 22kW Generac on natural gas burns about 2.8 – 3.5 therms per hour at full load. A 45kW liquid-cooled unit burns 6+ therms per hour. During a multi-day outage, that adds up. However, the difference between a properly sized 22kW and an oversized 30kW running the same house is meaningful — you are paying for unused capacity every hour the generator runs.
Not easily. The generator, transfer switch, and gas line are all sized together. Upgrading from 22kW to 30kW usually requires replacing the transfer switch, upgrading the gas line, and sometimes upgrading the electrical panel. It is almost as expensive as a new installation. That is why we always recommend sizing for your 10-year needs, not just your current load.