Home › Comparisons › Kohler vs. Generac on natural gas vs. propane
Home standby generators are sold by their propane (LP) rating, and most make less on natural gas. Among the models below, the loss runs from 0% (Generac 14 kW) to 14.3% (Kohler 14RCA). Generac’s newer NextGen models lose less than the older Guardian models of the same size, and the Kohler 26RCA matches the NextGen 26 kW at 24 kW.
Rated output on propane vs natural gas
| Model | Propane (LP) rating | Natural gas rating | Output lost on NG* |
|---|---|---|---|
| Generac Guardian 14 kW (7223/7224/7225)[1] | 14 kW | 14 kW | 0.0% |
| Generac NextGen 14 kW (7258)[2] | 14 kW | 14 kW | 0.0% |
| KOHLER 14RCA / 14RCAL[3] | 14 kW | 12 kW | 14.3% |
| Generac Guardian 18 kW[1] | 18 kW | 17 kW | 5.6% |
| Generac Guardian 20 kW (7038/7039)[4] | 20 kW | 18 kW | 10.0% |
| KOHLER 20RCA / 20RCAL[5] | 20 kW | 18 kW | 10.0% |
| Generac Guardian 22 kW (7042/7043)[4] | 22 kW | 19.5 kW | 11.4% |
| Generac NextGen 22 kW (7260)[6] | 22 kW | 21 kW | 4.5% |
| Generac Guardian 24 kW[4] | 24 kW | 21 kW | 12.5% |
| Generac NextGen 24 kW[6] | 24 kW | 22.5 kW | 6.2% |
| Generac Guardian 26 kW (7290/7291)[7] | 26 kW | 22.5 kW | 13.5% |
| Generac NextGen 26 kW (7327)[6] | 26 kW | 24 kW | 7.7% |
| KOHLER 26RCA / 26RCAL[8] | 26 kW | 24 kW | 7.7% |
| Generac NextGen 28 kW[6] | 28 kW | 25 kW | 10.7% |
* Calculated by us from each manufacturer’s published LP and natural gas ratings.
Why natural gas output is lower
Natural gas carries less energy per cubic foot than propane, so an engine that runs on both fuels makes less power on natural gas. The ratings also assume the gas arrives at the right pressure. Generac’s 22 kW Guardian needs 3.5–7 in. water column on natural gas and 10–12 in. on propane[4]; Kohler’s 20RCA lists 3.5–11 in. H₂O on natural gas and 7–11 in. on propane[5]. An undersized gas meter or pipe can cut output further.
Altitude and temperature derating
| Generac | KOHLER | |
|---|---|---|
| Per 1,000 ft of elevation | About 3.5%[7] | 4% above 500 ft[8] |
| Per 10 °F above 60 °F | About 1%[7] | 2%[8] |
| High-altitude kit | G007301-0 for use above 2,000 ft (26 kW)[7] | not listed on spec sheet |
Worked example (our calculation): at 5,000 ft, a 24 kW natural gas rating becomes about 19.8 kW using Generac’s 3.5%-per-1,000-ft rule (5 × 3.5% = 17.5%), and about 19.7 kW using Kohler’s 4%-per-1,000-ft-above-500-ft rule (4.5 × 4% = 18%). Confirm the exact derate with your dealer.
Running on propane instead
Propane gives the full rated output, but it comes from a tank on site, so runtime depends on the tank size. Propane use from the spec sheets:
| Model | Propane use at half load | Propane use at full load |
|---|---|---|
| Generac Guardian 22 kW[4] | 2.53 gal/hr (92 ft³/hr) | 3.90 gal/hr (142 ft³/hr) |
| Generac Guardian 26 kW[7] | 2.06 gal/hr (75 ft³/hr) | 3.63 gal/hr (132 ft³/hr) |
| Generac Guardian 14 kW[1] | 1.81 gal/hr (65 ft³/hr) | 3.07 gal/hr (112 ft³/hr) |
| Generac NextGen 14 kW[2] | 1.76 gal/hr (63 ft³/hr) | 2.92 gal/hr (106 ft³/hr) |
| KOHLER 20RCA[5] | 82 ft³/hr | 136 ft³/hr |
| KOHLER 26RCA[8] | 85 ft³/hr | 129 ft³/hr |
| KOHLER 14RCA[3] | 60 ft³/hr | 81 ft³/hr |
Kohler lists propane use only in cubic feet per hour; Generac lists both gallons and cubic feet.
Frequently asked questions
How much power does a generator lose on natural gas?
It depends on the model. Among current Kohler and Generac air-cooled models, the loss ranges from 0% (Generac 14 kW: 14 kW on both fuels) to 14.3% (Kohler 14RCA: 14 kW on propane, 12 kW on natural gas). The Generac Guardian 22 kW loses 11.4% (22 to 19.5 kW).
Which generator makes the most power on natural gas?
Among the models compared here, the Generac NextGen 28 kW, at 25 kW on natural gas. In the 26 kW class, the Kohler 26RCA and Generac NextGen 26 kW are tied at 24 kW.
Does altitude affect generator output?
Yes. Generac says about 3.5% per 1,000 ft; Kohler says 4% per 1,000 ft above 500 ft. Both also derate for temperatures above 60 °F.
Sources
Every figure on this page was taken from the documents below, all opened on October 27, 2026. Manufacturers revise spec sheets and prices; check the linked document before you buy.
- 1. Generac Guardian 10/14/18 kW spec sheet, Part A0000973374 Rev. A (10/22/2020) (accessed October 27, 2026)
- 2. Generac NextGen 14/18 kW spec sheet, Part A0005151081 Rev. B (07/11/2025) (accessed October 27, 2026)
- 3. KOHLER 14RCA/14RCAL spec sheet G4-270 (rev. 4/26j), Discovery Energy, LLC (accessed October 27, 2026)
- 4. Generac Guardian 20/22/24 kW spec sheet, Part A0000937814 Rev. E (03/15/2022) (accessed October 27, 2026)
- 5. KOHLER 20RCA/20RCAL spec sheet G4-272 (rev. 4/26j), Discovery Energy, LLC (accessed October 27, 2026)
- 6. Generac NextGen 22/24/26/28 kW spec sheet, Part A0005151077 Rev. B (07/11/2025). Generac document, copy hosted by retailer Global Industrial (the generac.com link did not resolve on Oct 27, 2026) (accessed October 27, 2026)
- 7. Generac Guardian 26 kW spec sheet, Part A0002026894 Rev. D (09/19/2022) (accessed October 27, 2026)
- 8. KOHLER 26RCA/26RCAL spec sheet G4-315 (rev. 4/26g), Discovery Energy, LLC (accessed October 27, 2026)