Load Management and Load Shedding for Standby Generators
Why this matters
Standby generators are sized for the home's electrical load - but a 30 kW home doesn't necessarily need a 30 kW generator. Load management systems (intelligent shedding) allow a smaller, more affordable generator to effectively backup a larger home by automatically dropping non-essential loads when generator capacity is reached. The math saves customers significantly on the generator purchase while still providing reliable backup. This reference covers how the systems work and when to specify them.
The problem load management solves
A typical 2,500 sq ft home may have:
- Central air conditioning: 4-5 kW (compressor + air handler)
- Electric water heater: 4.5 kW
- Electric dryer: 5 kW
- Electric range: 8-12 kW
- Refrigerator + lights + small loads: 2-3 kW
- Other: 1-2 kW
Total nameplate: 24-30+ kW. Backing this up with a 30 kW generator works but costs significantly more than a 20 kW unit.
The reality: customers don't simultaneously run all these loads at once during an outage. The dryer is rarely critical. The range is sometimes critical. The HVAC is usually critical. Load management automates the priority decisions.
How load shedding works
A load management system consists of:
- Generator controller with current sensing
- Smart breaker panels or transfer switch with built-in load management OR external load-management relay modules
- Configurable priorities assigned to each load (1 = always on, lowest priority sheds last)
- Automatic monitoring of generator output vs. capacity
When the generator runs:
- Monitor measures generator output current
- If output approaches capacity:
- Lowest priority load is dropped (relay disengages)
- Output drops; remaining loads continue
- As loads cycle off:
- The dropped load is restored (after a delay to verify capacity)
- Cycle continues throughout the outage
Result: the 20 kW generator effectively handles a 30 kW home by managing what runs when.
Priority categories
A typical priority assignment:
| Priority | Loads |
|---|---|
| 1 (Always on) | Refrigerator, sump pump, well pump, medical equipment |
| 2 (High) | HVAC blower, lights, communications |
| 3 (Medium) | HVAC compressor, water heater |
| 4 (Low) | Dryer, range, hot tub, EV charger |
The customer + technician decide priorities. Critical loads get priority 1; convenience loads get lower priority.
Load management systems by brand
Generac PowerManage Smart Switches:
- Wireless load management modules
- Each module monitors and controls one circuit
- Programmable priorities
- Available for various breaker types
- Integrates with Generac's controller
Kohler Smart Power Management:
- Built-in features on premium Kohler generators
- Configurable through the controller
- Module-based for circuit-specific control
External / third-party load management:
- Eaton MEM (Module-based Energy Management)
- Square D / Schneider Electric load shedding panels
- DSE (Deep Sea Electronics) controllers
- Provide vendor-independent solutions
Soft-start kit for HVAC compressor:
- Reduces the startup current of the AC compressor
- Allows a smaller generator to start the AC without a load management dance
- Often the cheapest path to "I can run the AC on a smaller generator"
When to recommend load management
| Customer situation | Recommendation |
|---|---|
| Home with substantial electrical loads, customer wants whole-home backup | Load management + appropriately sized generator |
| Home with high HVAC demand in heating / cooling season | Load management OR soft-start kit OR larger generator |
| Customer prioritizes "everything runs during outage" | Larger generator without load management (simpler, less to fail) |
| Customer is budget-conscious | Smaller generator + load management for the most critical loads |
| Home with EV charger | Load management essential (EV at 7 kW would dominate any generator) |
| Home with electric heating | Load management + larger generator OR strategic load priorities |
Sizing with load management
Generic example for the 2,500 sq ft home discussed earlier:
Without load management:
- Total nameplate: ~30 kW
- Generator: 30 kW or larger
- Generator carries all loads simultaneously
- Customer doesn't notice the outage
With load management:
- Total nameplate: ~30 kW
- Largest "always-on" load combination: ~12 kW (HVAC + refrigerator + lights + small loads)
- Generator: 20 kW (covers always-on with margin for cycling)
- Customer notices: dryer doesn't run during outage; range may be load-managed during peak HVAC
The load-managed approach reduces generator cost and physical footprint while still providing functional backup.
What the customer notices during operation
When load management is active during an outage:
- The HVAC may cycle differently than normal (load shedding may interrupt long compressor runs)
- The dryer may not run when AC is running
- The water heater may be delayed during peak loads
- Lighting and refrigeration are always on
- Customer may notice slight delays when starting multiple loads
The customer's experience is more "everything works but some things wait their turn" rather than "I'm in the dark for hours."
Load management vs. larger generator
The cost trade-off:
| Aspect | Smaller generator + load management | Larger generator without |
|---|---|---|
| Generator cost | Lower (smaller unit) | Higher (larger unit) |
| Installation cost | Similar | Similar |
| Load management cost | Additional (modules or smart panel) | None |
| Annual fuel use | Lower (more efficient unit at typical load) | Higher (larger engine) |
| Service cost | Lower (smaller engine) | Higher (larger engine) |
| Customer experience | Some loads cycle; functional backup | Seamless full-home operation |
| Risk during heat wave / extended outage | Lower margin for sustained heavy loads | Higher capacity reserve |
The breakdown over 15 years of ownership often favors load management for moderate-sized homes. Larger homes (5,000+ sq ft) typically need the larger generator regardless.
Soft-start kits
A soft-start kit (Hyper Engineering Micro-Air, others) is a specific solution for HVAC:
- Installed on the AC compressor's starting circuit
- Limits the inrush current at startup
- Reduces peak generator load by 50-70 percent during compressor start
- Allows a smaller generator to start the AC
For homes where the AC is the constraint (the generator is sized adequately for everything else, but the AC startup demand requires upsizing), the soft-start kit is often the cheapest answer.
Implementation procedure
For a new install with load management:
References
- NEC 700 / 701 / 702 (Emergency, Legally Required Standby, Optional Standby Systems)
- NFPA 110 (Emergency and Standby Power Systems)
- NFPA 37 (Stationary Combustion Engines)
- Manufacturer documentation (Generac PowerManage, Kohler, Eaton MEM)
- Hyper Engineering Micro-Air soft-start documentation
- Manuall internal: Portable vs. Standby Generator, Generator Sizing, Whole House Generator Install