Why Getting Generator Size Right Matters
Northwest Arkansas homeowners who invest in standby generators do so because they want their home to keep functioning during outages, whether from an ice storm in February or a severe thunderstorm in July. But the generator’s usefulness depends entirely on whether it is sized correctly for the home.
A generator that is undersized will overload when you run your HVAC alongside your refrigerator and a few lights. It may run but deliver unstable voltage that damages appliances. One that is dramatically oversized wastes money upfront and runs less efficiently under light load.
The sizing conversation should happen with a licensed electrician before you purchase the unit, not after it arrives.
How Generator Capacity Is Measured
Standby generators are rated in kilowatts. One kilowatt equals 1,000 watts. The generator’s rated kilowattage is the maximum continuous output it can deliver. Manufacturers also list a surge or peak rating, which is the maximum output for short bursts. Sizing should be based on continuous rated output, not surge capacity.
Your home’s electrical load is also measured in watts or kilowatts. A load calculation adds up the wattage of everything you want to run simultaneously, including the startup surge of motors in HVAC systems and appliances.
What Size Generator Does an NWA Home Need?
10 to 14 kW: Small Homes and Essential Circuits
A 10 to 14 kW standby generator handles a small home under 1,500 square feet with a single HVAC system. It powers lights, outlets, the refrigerator, and the HVAC system but may struggle if multiple large loads run simultaneously. This size is adequate for modest homes where the priority is keeping the essentials running, not full home coverage.
16 to 20 kW: The Most Common Size for NWA Residential
This is the range we install most often in Northwest Arkansas. A 16 to 20 kW generator comfortably covers a medium to large home with central HVAC, kitchen appliances, lights, outlets, and most everyday electrical loads running simultaneously. It has enough headroom to handle motor startup surges without strain.
For most single-family homes in Springdale, Fayetteville, Rogers, and Bentonville, a 20 kW generator provides excellent coverage with room to spare.
22 to 26 kW: Larger Homes and Higher Loads
Homes over 3,000 square feet, homes with multiple HVAC zones, or homes with high-draw specialty equipment like a well pump, EV charger, or large pool pump may need 22 to 26 kW. This size handles larger electrical loads without stress.
Above 26 kW: Very Large Homes or Multiple Structures
Generators above 26 kW are typically paired with 400-amp service or used for homes with accessory dwelling units, large shops, or commercial-scale equipment. These are less common in residential applications but are available when needed.
The Load Calculation: How Your Electrician Figures Out the Right Size
A load calculation is a formal process that adds up every electrical load in your home. Your electrician lists every circuit, identifies the wattage of equipment on each circuit, identifies which loads are continuous versus startup-only, and calculates total demand.
Key inputs that affect the calculation:
- HVAC system tonnage and startup draw (the biggest variable in most NWA homes)
- Electric water heater or other large 240-volt loads
- Well pump if present (significant startup surge)
- EV charger capacity
- Number of circuits and typical simultaneous usage
The result of the load calculation is a specific kilowatt recommendation, not a general range. That specific number is what you bring to the generator purchase.
Natural Gas vs Propane for Standby Generators in NWA
Most homes in Springdale, Fayetteville, Rogers, and Bentonville have natural gas service, making it the most convenient fuel for a standby generator. Natural gas connects directly to your home’s existing line. The generator runs indefinitely without refueling as long as the gas supply is active.
For rural NWA properties without natural gas, propane is the right choice. A correctly sized propane tank keeps the generator running for days during extended outages. Your propane supplier and electrician coordinate on tank sizing based on the generator’s consumption rate at expected load.
Ready to size and install a standby generator for your NWA home? Call NWA C&S Electric and we will do a load calculation and walk you through your options.
Frequently Asked Questions
What size generator do I need to run central air conditioning?
Central AC is the highest-draw load in most NWA homes. A 3-ton central AC unit draws about 3,500 to 4,000 watts running and may surge to 7,000 watts at startup. A generator sized for whole-home coverage with central AC needs to be at least 16 to 20 kW for average-sized homes.
Can a standby generator power an electric vehicle charger?
A Level 2 EV charger draws 40 to 50 amps continuously, which is a significant load. During an outage, most homeowners prioritize HVAC and home essentials over EV charging. If you want the option to charge during a generator outage, factor this into the load calculation and size up accordingly.
How long can a standby generator run continuously?
On natural gas, indefinitely as long as the gas supply is active. On propane, runtime depends on tank size and generator load. A 500-gallon propane tank at moderate load typically runs a standby generator for three to five days.
Does the generator size affect the installation cost?
Yes. Larger generators require larger gas lines, larger transfer switches, and more robust electrical connections. A 20 kW installation typically costs more than a 14 kW installation, but the difference is less significant than the generator unit price difference itself.
What if I buy a generator and it turns out to be undersized?
An undersized generator will overload under full home usage, causing voltage drops and potential damage to sensitive electronics. In severe cases, the generator itself can be damaged. The right approach is the load calculation before purchase, not discovering the issue during the first outage.
Size It Right and You Will Never Think About It During an Outage
A correctly sized standby generator runs quietly in the background during an outage and delivers everything your home needs without you having to make choices about what to turn off. That is the goal.
NWA C&S Electric handles standby generator sizing, installation, and transfer switch work across Springdale, Fayetteville, Rogers, Bentonville, Bella Vista, and the surrounding Northwest Arkansas area.
Call NWA C&S Electric: (479) 391-8655 | Schedule online at nwacselectric.com
