The Cummins RS20A reference identifies a specific residential standby configuration. Its model, part number and specification revision matter when comparing rated output or deciding whether transfer equipment is included.
Cummins RS20A questions answered: sizing, cost, fuel and maintenance
Cummins RS20A Specifications (Manufacturer Data)
| Specification | Cummins RS20A | Source |
|---|---|---|
| Models covered | RS20A (C20N6H, generator only); RS20AC (C20N6HC, with 200 A service-entrance ATS); RS20AE / RS20ACE extreme-cold versions | 1 |
| Rated output, natural gas | 18 kW (75 A at 240 V) | 2, 1 |
| Rated output, propane (LP) | 20 kW (83.3 A at 240 V) | 2, 1 |
| Engine | Cummins QSJ999G, naturally aspirated air-cooled V-twin, 999 cc, 3,600 rpm | 1, 2 |
| Dimensions (L × W × H) | 34.1 × 36.0 × 27.3 in (865 × 915 × 694 mm) | 1 |
| Weight | 531 lb (241 kg) RS20A; 596 lb (271 kg) RS20AC package | 1 |
| Sound level | 65 dB(A) at 23 ft (7 m) at normal load (quietest point) | 1 |
| Natural gas use, ½ load / full load | 172 / 268 ft³/hr | 1 |
| Propane use, ½ load / full load | 66 / 112 ft³/hr (LP vapor) | 1 |
| Main circuit breaker | Single 100 A | 1 |
| Transfer switch options | RS20AC includes a 200 A service-entrance ATS; Cummins ATSs are also sold separately in various amperages, service-entrance and non-service-entrance, indoor and outdoor (UL 1008) | 1 |
| Warranty | 5-year / 2,000-hour limited (generator); 2-year on RA automatic transfer switches; extended options available | 1 |
Cummins has published several revisions of this sheet with different weights and fuel figures. The table follows the October 2019 revision hosted on Cummins' own document library and the 2025 Cummins rating card; confirm the revision that matches the part number on your quote.
What the size and fuel figures mean for installation
Cummins lists the series as NFPA 37 compliant for installation 18 inches from a building. Its footprint is squarer than many air-cooled standby units: 34.1 in long by 36.0 in wide. On propane, 66 ft³/hr at half load converts to about 1.81 gal/hr using Cummins' factor of 36.39 ft³ per gallon, or roughly 131 gallons over a 72-hour outage (our arithmetic). See the propane tank sizing guide. (Source: 1.)
Specification sources, checked October 3, 2026:
Why the fuel distinction matters
At the documented 240 V rating, 75 A corresponds to 18 kVA and 83.3 A to approximately 20 kVA. Have the installer confirm the applicable real-power rating and starting performance for the actual set rather than assume the model name means identical output on both fuels.
Use the household sizing guide to organize your loads. Request the current specification sheet with the quote, particularly if the part number differs from the reference above.
Compare packages, not just the RS20 name
Ask whether transfer equipment is included, which loads will be managed and what the site needs for fuel supply. A generator-only offer and a complete installed-system quote are not directly comparable. Use the quote worksheet to separate equipment, electrical work, fuel work and commissioning.
We do not publish an invented current MSRP for this configuration. Obtain a dated equipment quote and keep its installation scope visible.
Compare alternatives and ongoing support
Read Generac vs. Cummins and Kohler vs. Cummins with the exact proposed models in hand. Ask who provides residential service at your address and which warranty work that provider handles.
For maintenance, obtain the matching operator’s manual through Cummins manual support. An older specification sheet is not a service schedule, and RV-generator instructions are not substitutes for this residential unit.
Return to the Cummins brand guide for the wider range. This is document research, not a hands-on test or a claim of superior reliability.
What evidence would resolve a different ordering code?
Ask the Cummins supplier for a specification sheet and package list matching the quoted ordering code, plus the applicable warranty and operator manual. Keep the older RS20A reference as historical context if those documents differ. The Cummins brand guide connects this equipment check to the broader buying decision.