Auxiliary Power: How to Reduce Fan, Pump & Drive Loss

Auxiliary power typically represents 6 to 10 percent of gross generation in coal and gas-fired plants, though the exact figure depends heavily on fuel type, cooling system design, and plant age. Coal plants with pulverizers, ash handling, and larger draft fan systems tend to sit at the higher end of that range, while combined cycle plants with fewer rotating auxiliaries often sit closer to the lower end. Plants that have never conducted a dedicated auxiliary power audit are frequently surprised to find their actual figure is a full percentage point or two above what their design documentation assumed, simply because equipment has drifted out of its original efficient operating band over years of service. Establishing an accurate current baseline through submetering is the first step in any reduction program, since reduction targets set against outdated design assumptions tend to understate the real opportunity. Book a demo to get a baseline audit for your plant.

A motor replacement swaps an aging or standard-efficiency motor for a newer, more efficient one, but it does not change how that motor is controlled, so a fixed-speed motor still runs at full speed regardless of process demand. A VFD retrofit instead adds a variable frequency drive between the electrical supply and the motor, allowing the motor's rotational speed to vary continuously in response to actual flow or pressure requirements. Because pump and fan power consumption scales roughly with the cube of speed, even a 20 percent reduction in required speed at part load can cut power draw by close to half. The two approaches are complementary rather than competing, and many plants achieve the best return by pairing a VFD retrofit with a premium-efficiency motor replacement during the same outage window to capture both savings mechanisms at once. Contact support to evaluate which assets are the best retrofit candidates.

Boiler feed pumps, forced and induced draft fans, and circulating water pumps are usually the highest priority because they run continuously at high load and account for the largest single share of total auxiliary consumption in most fossil-fired plants. Within that group, equipment that is currently controlled through throttling valves or inlet dampers rather than variable speed drives represents the largest untapped opportunity, since the gap between actual and theoretical minimum power tends to be widest on throttled systems. A structured prioritization exercise ranks candidate assets by their annual savings potential, calculated from baseline power data and duty cycle analysis, rather than simply targeting the largest motors on the site. This ensures capital is directed toward the assets that will pay back fastest rather than the ones that are simply easiest to access during an outage. Book a demo to rank your assets by savings potential.

Yes, most auxiliary power reduction projects can be scheduled around individual equipment tags rather than requiring a full plant outage. Submetering installation, VFD retrofits on non-critical pumps, and continuous monitoring deployment are typically completed during normal maintenance windows or short planned outages for the specific equipment involved. Larger interventions such as fan wheel replacements or major motor swaps on critical path equipment like boiler feed pumps are usually scheduled to align with a planned outage to avoid any risk to unit availability, but even these projects rarely require extending the outage duration since the work can proceed in parallel with other planned outage activities. A phased approach that starts with lower-risk, non-critical equipment also allows plants to validate savings and build internal confidence before tackling equipment on the critical path. Contact support to plan a low-disruption implementation schedule.

Even after a successful VFD retrofit or right-sizing project, auxiliary power consumption can creep back upward over time as bearings wear, couplings drift out of alignment, or impellers foul with scale and debris, each of which forces the motor to draw more current to deliver the same output. Continuous AI-driven monitoring tracks each asset's power draw against its expected baseline for the current operating condition and flags any deviation as soon as it appears, rather than waiting for the next scheduled efficiency test to catch the drift. This turns auxiliary power management from a one-time project into an ongoing discipline, ensuring the savings captured during the initial program are sustained for years rather than eroding back toward the original baseline within eighteen to twenty-four months, which is a common pattern in plants that treat auxiliary power as a one-off initiative. Book a demo to see continuous auxiliary monitoring in action.