FEMA pays an hourly rate for the time your equipment is actually operating on eligible work, including permanently mounted generators. Vehicles can be paid by documented mileage if that costs less. If you had to buy equipment to respond, FEMA can fund the purchase plus either the hourly rate or actual fuel and maintenance.
Source: PAPPG Table 12.
Log equipment hours daily alongside the operator’s timesheet. Reconstructing logs later is the most common gap.