Overview#
The Cummins RS40 is a 40 kW liquid-cooled residential standby generator and the most powerful model in the QuietConnect RS Series 2.4-liter platform. The turbocharged and aftercooled inline 4-cylinder engine delivers 40 kW at 120/240V (166.7 amps on both fuels), making it the top choice for estate homes and large residences that need maximum capacity from a compact residential generator.
The RS40 runs on natural gas or propane vapor (field selectable) at 1,800 rpm. With the Sound Level 2 enclosure it produces just 63 dB(A) at 23 feet; the Sound Level 1 enclosure produces 68 dB(A). The enclosure is wind-rated to 180 mph per ASCE 7-10 and the unit handles cold weather starts down to -40 F with factory-installed coolant heater and crankcase vent heater.
At 1,356 lbs and 94 x 34 x 45.5 inches, the RS40 shares the same footprint as the RS36 but weighs slightly more. Natural gas consumption at full load is 519 CFH. PowerCommand 1.1 controls provide electronic governing, self-diagnostics, and remote monitoring.
Technical Specifications#
| Parameter | Value |
|---|---|
| Standby Rating | 40 kW |
| Voltage (1-phase) | 120/240V |
| Voltage (3-phase) | 120/208V, 277/480V |
| Frequency | 60 Hz |
| Rated Amps (1-phase, both fuels) | 166.7 |
| Engine Displacement | 2.4 L (143.5 in³) |
| Cylinders | 4 (inline) |
| Bore x Stroke | 86.5 mm x 100.0 mm |
| Aspiration | Turbocharged and aftercooled |
| Rated Speed | 1,800 rpm |
| Cooling | Liquid-cooled |
| Controller | PowerCommand 1.1 |
| Sound Level (SL2 / SL1) | 63 / 68 dB(A) at 23 ft |
| Dimensions (L x W x H) | 94.0 x 34.0 x 45.5 in |
| Weight | 1,356 lbs |
| Wind Rating | 180 mph (ASCE 7-10) |
| Cold Weather | -40 F (with factory accessories) |
Fuel consumption at full load:
| Fuel | Consumption |
|---|---|
| Natural Gas | 519 CFH (14.5 m³/hr) |
| LP Vapor | 193.6 CFH (5.4 gal/hr) |
Our Service Experience#
The RS40 is the top of the 2.4L platform line and is popular for luxury homes and small commercial applications that need more than 30 kW but want to avoid the larger and heavier 5.9L engine platform. The turbocharged engine runs at higher boost levels than the RS36, so turbocharger inspection is particularly important at annual service.
Service intervals are identical across the 2.4L range: oil and filter at 500 hours or annually, air filter at 500 hours, spark plugs at 1,000 hours. The coolant heater must stay plugged in at all times. We recommend the Sound Level 2 enclosure upgrade for installations near property lines or in noise-sensitive neighborhoods -- the 5 dB reduction from 68 to 63 dB(A) is noticeable.
For loads that exceed 40 kW, the next step up is the RS50 -- a significantly larger unit with a 5.9L inline 6-cylinder engine weighing 2,403 lbs. This is a major jump in size, weight, and installation cost.
Frequently Asked Questions#
What is the standby rating of the RS40? 40 kW at 120/240V single phase (166.7 amps). Also available in three-phase configurations.
How does the RS40 compare to the RS50? The RS40 uses a 2.4L turbo inline-4 (1,356 lbs); the RS50 steps up to a 5.9L inline-6 (2,403 lbs). The RS50 provides 25% more power but nearly doubles the weight and footprint. Choose the RS40 when 40 kW is sufficient; choose the RS50 when you need more capacity or want the engine to run at a lower percentage of its rated output.
What is the warranty on the RS40? 2-year limited warranty from Cummins. Extended options available up to 10 years.
