Continuous Load: The 125 Percent Sizing Trigger
A continuous load is a load expected to run at its maximum current for three hours or more, so conductor and overcurrent sizing usually treat that current at 125 percent.
Continuous load is easy to over-apply because the multiplier is memorable. The useful distinction is narrower: use 125 percent when selecting conductors and overcurrent protection for the continuous portion, but do not treat that adjusted number as the measured current for every other check.
What gets multiplied
The continuous part of the load is multiplied by 125 percent for conductor and overcurrent sizing. The non-continuous part is added at 100 percent.
For a 32 A continuous charger and 8 A of non-continuous load, the sizing current is 48 A: 40 A for the charger portion plus 8 A for the other load.
Why voltage drop is different
Voltage drop is based on current through conductor impedance over distance. If the equipment draws 32 A, the drop calculation uses 32 A unless a design choice intentionally uses another current.
That is why a circuit can need a larger breaker from continuous-load sizing and a larger conductor from voltage-drop performance for different reasons.
Where the shortcut fails
The phrase 125 percent does not turn every connected load into a continuous load. Cycled, intermittent or standby loads need their own classification.
When a page or nameplate gives MCA, MOCP or a listed instruction, treat that product information as the starting point rather than rebuilding the rule from memory.
Where the Term Decides Something
Four points in the work where the figure is the answer to a question, not vocabulary.
EV charger branch circuits
A 48 A EVSE output is treated as a 60 A sizing load, which is why a 48 A charger belongs on a 60 A circuit when the equipment is configured that way.
Mixed branch-circuit loads
Only the continuous portion receives the 125 percent multiplier. Non-continuous load is added at 100 percent before the breaker and conductor are checked.
Breaker compatibility checks
The breaker must be at least large enough for the adjusted sizing current, then the selected conductor must still be allowed to be protected by that breaker.
Service load review
Continuous equipment can affect a dwelling or feeder calculation, but the treatment belongs inside the specific load-calculation method in use.
Which Figure to Use
Reading the term correctly in practice.
Separate sizing current from operating current
Use the 125 percent value to size conductors and overcurrent protection. Use actual expected current when estimating voltage drop unless the load really operates at the adjusted value.
Do not multiply the whole panel
Apply the multiplier to continuous portions, not to every load on a panel schedule by habit.
Watch nameplate MCA values
When equipment provides a minimum circuit ampacity, that value may already include required continuous-load treatment. Do not add another 125 percent unless the instructions require it.
Use the adopted edition
The site defaults to NEC 2023, but the AHJ-adopted edition and equipment listing decide how a specific project is documented.
FAQs
What is the three-hour continuous-load rule?
Do I use 125 percent for voltage drop?
How do I handle mixed continuous and non-continuous loads?
Can equipment nameplate values already include the multiplier?
Calculated against the NEC 2023 edition using 210.19(A)(1), 210.20(A), 215.2(A)(1). Confirm the edition adopted by your AHJ, which may differ and may carry local amendments.
Not covered by this tool
- Equipment MCA, MOCP and listing instructions that already include sizing treatment.
- Intermittent, cyclic or standby loads that are not continuous at maximum current.
- Voltage-drop calculations, which use the actual design current selected for the run.
Data last verified