How to Choose a Home Generator: Complete Buyer's Guide 2026

Step 1: Decide What You Want to Power

The first question is not "which generator should I buy?" — it is "what do I need to power during an outage?" The answer determines the kilowatt size you need, which in turn drives most other decisions.

There are three common approaches to generator sizing:

Essential circuits only: Power the refrigerator, a few lights, the HVAC, and the well pump. This requires 10–14 kW and is the most affordable approach. It is appropriate for homeowners who want basic comfort and food preservation during short outages.

Whole-home coverage: Power everything in the house simultaneously — all HVAC zones, electric range, water heater, all lights, and all appliances. This requires 18–26 kW depending on home size and is the right choice for extended outages or homeowners who do not want to think about load management.

Whole-home with smart load management: Use a smart transfer switch to power everything but cycle non-critical loads when the generator approaches capacity. This allows a 18–20 kW generator to effectively cover a home that would otherwise need 24–26 kW. It is the best value approach for larger homes.

Step 2: Calculate the Right Kilowatt Size

Use this simple formula to estimate your generator size requirement: add up the wattage of everything you want to run simultaneously, then add 20% for startup surge capacity (motors like AC compressors draw 2–3x their running wattage at startup).

Appliance	Running Watts	Startup Surge
Central AC (3-ton)	3,500W	7,000–9,000W
Electric furnace	10,000W	12,000W
Well pump (1 HP)	750W	2,000W
Refrigerator	150W	600W
Electric range	2,000–5,000W	2,000–5,000W
Water heater (electric)	4,500W	4,500W
Lighting (whole home)	500–1,500W	500–1,500W
Sump pump	800W	1,300W

For most 2,000 square foot homes with central AC, a well pump, and standard appliances, the total running load is approximately 15,000–18,000 watts. Adding 20% for surge gives a requirement of 18,000–21,600 watts — which points to an 18–22 kW generator. Use our free sizing calculator for a more precise estimate based on your specific home.

Step 3: Choose Your Fuel Type

Natural gas is the preferred fuel for most standby generators. It is delivered via underground pipeline, so there is no tank to fill or run out of. Natural gas generators can run indefinitely during an extended outage as long as the gas supply is maintained. The main limitation is that natural gas is not available in all areas, particularly rural locations.

Propane (LP) is the alternative for homes without natural gas service. Propane generators require a dedicated tank (typically 250–500 gallons for a whole-home unit) and must be refilled periodically. A 500-gallon tank provides approximately 5–7 days of whole-home coverage. The advantage of propane is that it can be stored on-site, making it independent of utility infrastructure.

Dual-fuel generators can run on either natural gas or propane. They are useful for homeowners who have natural gas service but want propane as a backup, or who want flexibility. Dual-fuel units cost slightly more but provide maximum fuel security.

Step 4: Choose a Brand

For most homeowners, the choice comes down to Generac or Kohler. Generac has approximately 70% of the US residential market and the widest installer network. Kohler is the premium alternative — quieter, more refined, and slightly more expensive. Both offer 5-year warranties and strong track records.

Other brands worth considering include Cummins (commercial heritage, strong propane performance), Briggs & Stratton (budget-friendly, shorter warranty), and Honeywell (Generac-built units sold under the Honeywell brand). See our detailed brand comparison for a full side-by-side analysis.

Step 5: Select the Right Transfer Switch

For a standby generator, you need an automatic transfer switch (ATS) — it detects outages and switches power automatically. The standard for whole-home coverage is a 200-amp ATS, which is typically included in the generator package price. If you have a larger home or want smart load management, consider upgrading to a smart transfer switch.

For portable generators, a manual transfer switch is a safer and code-compliant alternative to extension cords. A 6–10 circuit manual transfer switch costs $400–$1,100 installed and connects your most critical circuits to the generator.

Step 6: Find and Vet an Installer

Generator installation requires licensed electricians and gas fitters. Always verify that your installer is licensed in your state, carries liability insurance, and is a certified dealer for the brand you are purchasing. Manufacturer certification matters because it affects warranty coverage — most brands require dealer-performed installation to maintain the full warranty.

Get at least three quotes. Installation prices for the same generator can vary by $2,000–$4,000 between contractors in the same market. Ask each contractor for an itemized quote showing the generator unit cost, transfer switch, labor, permits, and any additional materials separately.

Step 7: Plan for Maintenance

A standby generator requires annual maintenance to remain reliable: oil change, air filter replacement, spark plug inspection, battery check, and a full-load test. Most manufacturers require annual dealer-performed maintenance to maintain warranty coverage. Budget $150–$300 per year for maintenance costs.

Your generator will also run a weekly self-test (typically 5–10 minutes) to verify it starts and operates correctly. This is normal and expected — do not be alarmed when you hear it running on a quiet Tuesday morning.

Ready to Get Started?

Use our free sizing calculator to get a personalized kilowatt recommendation for your home, then use our free quote tool to get matched with certified installers in your area. You can also explore our brand comparison page for a detailed Generac vs Kohler analysis, or browse our local cost guides for state-specific pricing data.