How to Size a Kohler Generator: The Quick Answer

For most homes under 2,500 sq ft, a Kohler 20RESCL (20 kW) is the right choice. Homes between 2,500–4,000 sq ft typically need the Kohler 26RCL (26 kW). Homes over 4,000 sq ft or with central air conditioning above 5 tons should consider the Kohler 38RCL (38 kW) or higher. The exact size depends on your critical loads — the appliances and systems you need running during an outage.

Step 1: Identify Your Critical Loads

The first step in sizing any standby generator is identifying which systems you need to power during an outage. Kohler divides these into three tiers:

Load Tier	Typical Appliances	Estimated Watts
Essential	Lights, refrigerator, sump pump, phone charging	3,000–5,000W
Comfort	Essential + HVAC, water heater, microwave	8,000–14,000W
Whole Home	Comfort + electric range, dryer, EV charger	18,000–30,000W+

Most homeowners choose the "Comfort" tier — they want their HVAC running but don't need to power every appliance simultaneously. This typically points to a 20–26 kW Kohler generator.

Step 2: Calculate Your Starting Wattage

The most common sizing mistake is forgetting about starting watts vs. running watts. Motors (like those in air conditioners, well pumps, and refrigerators) require 2–3x their running wattage to start. Kohler generators are rated at their continuous output, so you need to account for these surge demands.

Here's how to calculate your starting wattage requirement:

1. List all appliances you want to run simultaneously
2. Note the running watts for each (found on the nameplate or owner's manual)
3. Identify the appliance with the highest starting surge (usually your central AC)
4. Add: (sum of all running watts) + (starting surge of largest motor) = minimum generator size

Example for a 2,200 sq ft home:

Appliance	Running Watts	Starting Watts
Central AC (3 ton)	3,500W	8,750W
Refrigerator	150W	600W
Furnace blower	800W	2,400W
Lights + outlets	1,500W	1,500W
Well pump (1 HP)	750W	2,250W
Total	6,700W running	+8,750W AC surge

Minimum generator size: 6,700W + 8,750W surge = ~15,450W peak demand. A Kohler 20RESCL (20 kW) handles this with 4,550W of headroom — the right choice for this home.

Step 3: Match to the Right Kohler Model

Kohler's residential standby lineup covers 14 kW to 150 kW. For most homes, these are the relevant models:

Model	Output	Best For	Price Range (Installed)
Kohler 14RESAL	14 kW	Small homes, essential loads only	$7,500–$11,000
Kohler 20RESCL	20 kW	Most homes under 2,500 sq ft	$9,500–$14,000
Kohler 26RCL	26 kW	Homes 2,500–4,000 sq ft	$11,500–$17,000
Kohler 38RCL	38 kW	Large homes, multiple AC units	$15,000–$22,000
Kohler 48RCL	48 kW	Luxury homes, home offices, EV charging	$18,000–$28,000

Step 4: Consider Your Fuel Type

Kohler standby generators run on natural gas or liquid propane (LP). The fuel type affects both the available output and the installation cost:

• Natural gas: Convenient (no tank), lower fuel cost, but output is typically 5–10% lower than LP rating. Requires proximity to a gas main.
• Liquid propane: Full rated output, works anywhere, but requires a propane tank (250–500 gallon recommended). Tank rental adds $50–$150/year.

Kohler's 20RESCL, for example, produces 20 kW on LP and 18 kW on natural gas at standard conditions. For most homeowners, natural gas is the preferred choice for its convenience and lower ongoing cost.

Step 5: Account for Future Load Growth

One of the most common regrets among generator buyers is undersizing. Consider these future additions when sizing:

• EV charging: A Level 2 charger draws 7,200W (30A). If you plan to own an EV, add this to your load calculation.
• Home additions: Adding a room or finishing a basement increases your HVAC load.
• Hot tub or pool equipment: These draw 3,000–6,000W continuously.

Kohler's general recommendation is to size up by 20% beyond your calculated peak demand to ensure the generator runs at 80% capacity or less — this extends engine life and reduces fuel consumption.

Kohler 20kW vs 26kW: Which Should You Choose?

This is the most common decision point for homeowners. Here's a direct comparison:

Factor	Kohler 20RESCL	Kohler 26RCL
Output	20 kW (LP) / 18 kW (NG)	26 kW (LP) / 24 kW (NG)
Home size	Up to 2,500 sq ft	2,500–4,000 sq ft
AC capacity	Up to 4 tons	Up to 5 tons
Noise level	67 dB	67 dB
Price difference	—	+$2,000–$3,500 installed
Fuel consumption	2.1 gal/hr (LP at full load)	2.7 gal/hr (LP at full load)

Choose the 20RESCL if: Your home is under 2,500 sq ft, you have a single-zone HVAC system under 4 tons, and you don't plan to add significant electrical loads in the next 10 years.

Choose the 26RCL if: Your home is 2,500–4,000 sq ft, you have a 4–5 ton AC system, or you want extra headroom for future loads. The $2,000–$3,500 premium is worth it for peace of mind.

Get a Professional Load Calculation

While this guide gives you a strong foundation, the most accurate sizing comes from a professional load calculation performed by a Kohler-certified installer. They will use Kohler's proprietary sizing software to account for your specific electrical panel, local utility voltage, and climate conditions.

Most Kohler dealers offer free in-home consultations and load calculations. Use our tool below to get matched with certified Kohler installers in your area who can provide an accurate sizing recommendation and a no-obligation quote.

For more context on how Kohler compares to Generac at each size tier, see our Kohler vs Generac full comparison. To get a rough cost estimate before speaking with an installer, try our home generator cost calculator.