15 kW Generator
A 15 kW standby generator sits at the lower end of whole-home coverage — enough for essential circuits and smaller homes with careful planning, but typically not enough for large central air systems without load management.
Quick Answer
A 15 kW standby generator can typically cover essential circuits — refrigerator, lighting, sump pump, well pump, furnace blower, and some small appliances — in a smaller home. It may support a smaller central AC system with load management, but homes with larger HVAC loads, electric resistance heat, or multiple high-draw appliances generally require 18–22 kW or more for reliable whole-home coverage. A load calculation is required to verify.
Coverage depends on simultaneous demand and starting surges — a load calculation using your actual appliances is required to confirm.
Central air conditioning is typically the largest single load in a home, and its compressor starting surge can be 3–4x the running wattage. A 15 kW generator may support a 2-ton (24,000 BTU) central AC system at moderate load, but a 3-ton or larger system often pushes beyond what a 15 kW unit can handle reliably without a load management module. Mini-split systems tend to have lower starting surges and may be more compatible with a 15 kW unit than conventional central AC compressors.
At 15 kW, natural gas consumption runs approximately 1.6–2.0 cubic feet per kilowatt-hour under load. Propane consumption at 50% load runs roughly 1.0–1.3 gallons per hour — a 250-gallon propane tank provides approximately 4–6 days of runtime at that rate. Verify consumption rates with the manufacturer's documentation for the specific model.
15 kW units are physically smaller than 20+ kW models, which can be an advantage on tight lots with limited clearance space. The pad footprint is smaller, and in some jurisdictions, smaller units may have reduced setback requirements. Transfer switch installation and permitting follow the same general process as larger units — expect 3–8 weeks from contract to final inspection.
A 15 kW generator at 240V draws roughly 62 amps at full output. Most modern 200-amp panels accommodate this without service upgrades. With 100-amp service, the total available capacity is more constrained and a panel assessment is important before choosing any generator size.
Verify sizing with your actual loads
The Generator Size Calculator and Electrical Load Worksheet give you a more accurate result than any size-based rule of thumb.
