Representative electrical demand
Septic and ejector pumps are intermittent motor loads that may be essential during a prolonged outage. Horsepower and pump type vary widely, so the equipment nameplate should be used for final sizing.
How this load affects generator size
For a dedicated portable-generator calculation, this load may be one of only a few items. For a whole-home standby system, it should be added to the other loads that may run at the same time. Motor-driven equipment also requires attention to startup surge.
Running watts versus starting watts
Resistive heating loads tend to have little startup surge but can consume several kilowatts continuously. Motors and compressors can have a much larger momentary starting requirement than their normal running demand. That difference is why two appliances with similar running watts can affect generator sizing very differently.
Ways to keep the generator smaller
- Prioritize truly essential loads during an outage.
- Use approved load-management controls for discretionary high-wattage circuits.
- Stagger motor starts where the control system allows it.
- Verify whether the appliance has a lower-power operating mode.
Add household loads to the sizing calculator →
Frequently asked questions
Can a portable generator run a septic or sewage ejector pump?
Possibly, if its continuous and surge ratings exceed the appliance demand and the connection is made safely using approved equipment. Never backfeed a home through an outlet.
Does a septic or sewage ejector pump determine whole-house generator size by itself?
Usually not. Whole-home sizing must consider all loads that may operate together, especially HVAC, pumps and large electric heating appliances.
Should I use the watts printed on the appliance?
Yes when available. Equipment nameplate or manufacturer electrical data is more reliable than a generic online estimate.