NEC Continuous Load 125% Rule Lookup
The continuous-load rule is the field checkpoint that prevents a long-running load from being sized as if it were a short-duration load. Use it before trusting a breaker size, conductor ampacity, feeder result, or EV charger circuit recommendation.
| Field Item | NEC Reference | Field Meaning |
|---|---|---|
| Continuous load definition | NEC Article 100 | A load expected to run at maximum current for three hours or more is treated differently from a short-duration load. |
| Branch-circuit conductors | NEC 210.19(A)(1) | Branch-circuit conductor sizing must account for the noncontinuous load plus 125% of the continuous load, subject to applicable equipment and code conditions. |
| Branch-circuit overcurrent protection | NEC 210.20(A) | The breaker or fuse rating is checked against the noncontinuous load plus 125% of the continuous load unless a listed 100%-rated assembly condition applies. |
| Feeder conductors | NEC 215.2(A)(1) | Feeder conductor sizing uses the same continuous-load concept before final ampacity, terminal, and installation checks. |
| Feeder overcurrent protection | NEC 215.3 | Feeder OCPD sizing must account for continuous and noncontinuous portions of the load, not only the nameplate or calculated total. |
| EV charging load | NEC 625.42, NEC 210.19(A)(1), NEC 210.20(A) | EV charging equipment is commonly reviewed as a continuous load. A 48A EVSE load, for example, screens at 60A before final conductor and equipment checks. |
| 100%-rated equipment exception | NEC 210.20(A), NEC 215.3 | The 125% sizing step may be handled differently only where the assembly and overcurrent devices are listed for operation at 100% of rating. |
Field Example
Applying the 125% Continuous-Load Rule
Use the continuous-load rule before selecting the branch-circuit or feeder rating. The field math is:
Continuous-load sizing basis = continuous load × 125%
Field example: a 40A continuous load is sized on a 50A basis before the overcurrent device and conductor ampacity are checked. For EVSE circuits, the same idea often turns a 32A charging output into a 40A circuit basis or a 48A charging output into a 60A circuit basis. Use the Breaker Size Calculator for general breaker screening and the EV Charger Circuit Sizing tool when the load is EVSE-specific.
Field Workflow
Continuous Load Workflow
Avoid treating the rule as a loose “80% breaker” shortcut. The NEC sizing path starts with the load type, separates continuous from noncontinuous portions, then checks conductors and overcurrent protection against the calculated basis.
Classify the load. Decide whether the load is expected to run at maximum current for three hours or more.
Separate load portions. Keep continuous and noncontinuous load portions separate instead of applying 125% to every amp automatically.
Apply the sizing basis. Use noncontinuous load plus 125% of continuous load for the conductor and OCPD checks where required.
Verify final limits. Check ampacity, terminal temperature, standard OCPD sizes, equipment markings, and listed 100%-rated conditions before relying on the result.
Sizing Logic
Sizing Basis
A continuous load is not just a larger number on the panel schedule. It changes the sizing basis because the circuit is expected to carry that current for an extended period. That is why a load that appears to fit a breaker at 100% may still require the next circuit size after the continuous-load calculation is applied.
The field sequence should stay clear: identify the actual load, classify continuous and noncontinuous portions, calculate the required sizing basis, then check conductor ampacity, terminal temperature limits, equipment instructions, and overcurrent protection rules.
Screening Formula
Required basis = noncontinuous load + (continuous load × 125%)
Final use still has to respect standard OCPD sizes, conductor ampacity, terminal temperature limits, equipment markings, and local requirements.
EV Charging Check
EV Charging Check
EV charging equipment is commonly evaluated as a continuous load. That is why a 32A EVSE commonly screens to a 40A circuit basis, and a 48A EVSE commonly screens to a 60A circuit basis before final field checks.
Circuit size is not the only approval point. After the continuous-load step, the installation still needs conductor ampacity, terminal temperature, wiring method, GFCI, disconnect, manufacturer instructions, panel capacity, and AHJ review where applicable.
Use the EV-specific reference when the load is EVSE. Review NEC 625 EV Charger Circuit Sizing before relying on the continuous-load result by itself.
Calculator Use
TradeHub Calculator Application
TradeHub calculators treat the continuous-load rule as a load-basis step before breaker, conductor, terminal, and EVSE equipment checks are trusted.
Related TradeHub Calculators
Field Checks
Common Field Misses
Using an 80% shortcut without checking the actual rule. The sizing path is noncontinuous load plus 125% of continuous load, with specific listed-equipment exceptions.
Applying 125% to the wrong load portion. Mixed loads need continuous and noncontinuous portions separated before the calculation is trusted.
Sizing the breaker but not rechecking the conductor. Continuous-load logic can change both the OCPD basis and the conductor ampacity review.
Forgetting terminal temperature limits after the load calculation. A circuit can pass the 125% load basis and still fail a 60°C or 75°C terminal ampacity check.
Assuming every installation qualifies for 100% rated operation. The exception depends on listed equipment and assembly conditions, not a preference to use the breaker at full nameplate load.
Related References
Related NEC Field References
Source Scope
Source Alignment and Use Scope
This field reference is based on NEC Article 100, 210.19(A)(1), 210.20(A), 215.2(A)(1), 215.3, 625.42, and related TradeHub source alignment records. It is for screening and planning only and does not replace the adopted NEC, local amendments, equipment markings, manufacturer instructions, listed 100%-rated equipment conditions, engineered design documents, or AHJ review. Review the TradeHub Code Citation & Source Log for source alignment records and the TradeHub Methodology page for how field references are scoped.
Field FAQ
Continuous Load FAQ
What makes a load continuous under the NEC?
A continuous load is generally one where the maximum current is expected to continue for three hours or more. That classification changes how the circuit load is counted for conductor and overcurrent sizing checks.
Does the 125% rule mean I always use an 80% breaker limit?
No. The field shortcut may describe the result for many standard breakers, but the NEC calculation is based on the noncontinuous load plus 125% of the continuous load, with specific exceptions for listed 100%-rated assemblies.
Why does a 48 amp EV charger often use a 60 amp circuit?
EV charging equipment is commonly treated as a continuous load. Multiplying 48 amperes by 125% gives 60 amperes before final conductor, terminal, equipment marking, and local-code review.