Can I Run This On That? - Electrical Load Checker
Compare an entered appliance load with breaker capacity and local conductor-table screening data. Verify the adopted electrical rules and actual installation separately.
Compare entered appliance loads with breaker capacity and local conductor-table rows. The local NEC data is a source-gap screen. Green results still require nameplate, listing, installation-condition, adopted-code and AHJ verification; they do not approve an installation.
Need to size the wire for a new dedicated circuit? This pairs directly with your load check
Wire Sizing →Planning a generator? Screen running and starting watts, then verify the setup
Generator Planning →Run a full panel load study to see how much total capacity you have left
Panel Load Study →Check conduit fill if you are pulling new conductors to add the dedicated circuit
Conduit Fill →How It Works
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Enter Circuit Breaker Size
Check your electrical panel and enter the amp rating of the breaker feeding the circuit you want to use. Common residential sizes are 15A (lighting), 20A (receptacles), 30A (dryers), and 50A (ranges).
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Select Wire Gauge
If you know the wire gauge, enter it. If you do not, the calculator uses the standard gauge for your breaker size: 14 AWG for 15A, 12 AWG for 20A, 10 AWG for 30A. The wire gauge determines the maximum safe ampacity.
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Enter Your Load
Enter the wattage or amperage of the appliance, tool, or equipment you want to plug in. Check the nameplate label on the device for exact ratings. For multiple items on the same circuit, enter the total combined load.
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Review the Load Screen
Compare the appliance load with breaker capacity and conductor ampacity, then review the load ratios. The result does not replace an electrician's check of the actual installation.
Built For
- Homeowners checking if a 1,500W space heater is safe on an existing circuit
- Workshop owners adding a table saw or air compressor to an existing garage circuit
- Tenants checking if a window AC unit can run on an apartment bedroom circuit
- EV charger feasibility checks before hiring an electrician for a dedicated circuit
- Kitchen appliance planning: can the existing 20A circuit handle a new countertop oven?
- Home office setups with multiple monitors, computers, and laser printers on one circuit
- Checking if an existing circuit is already overloaded before adding anything new
Features & Capabilities
NEC 80% Continuous Load Rule
Applies the NEC requirement that continuous loads (those running 3+ hours) must not exceed 80% of the circuit breaker rating. A 15A breaker can handle 15A for brief periods but only 12A continuously. This is the rule most people do not know about and the one that matters most for heaters, AC units, and grow lights.
Wire Gauge Ampacity Check
Compares the entered gauge with local ampacity rows. It cannot verify the installed conductor, listing, terminations or installation conditions.
Voltage Selection
Supports 120V, 208V, 240V, and other common voltages. Automatically converts between watts and amps based on the voltage you select so you can enter whichever unit is shown on the appliance nameplate.
Load Ratios and Review Notes
Shows the entered load as a percentage of the selected capacity and gives review notes. Treat the result as a screen before qualified installation review.
Conservative Screening Bias
The app applies a conservative bias to local screening data. That bias does not verify code compliance or determine whether an installation is safe.
Multi-Load Support
Enter total combined wattage when you want to check multiple appliances on the same circuit. Helps identify circuits that are safe for each individual load but dangerously overloaded when everything runs at the same time.
Comparison
| Circuit Breaker | Wire Gauge (Min.) | 80% Continuous Max | Typical Loads |
|---|---|---|---|
| 15A / 120V | 14 AWG | 12A (1,440W) | Lighting, small appliances |
| 20A / 120V | 12 AWG | 16A (1,920W) | Kitchen countertop, bathroom, general receptacles |
| 20A / 240V | 12 AWG | 16A (3,840W) | Window AC, small shop tools |
| 30A / 240V | 10 AWG | 24A (5,760W) | Clothes dryer, water heater |
| 40A / 240V | 8 AWG | 32A (7,680W) | Electric range, large cooktop |
| 50A / 240V | 6 AWG | 40A (9,600W) | Electric range, EV charger, sub-panel |
| 60A / 240V | 6 AWG | 48A (11,520W) | Sub-panel feeder, large equipment |
Assumptions
- Circuit breaker rating assumed to be the nameplate ampere value with no derating for ambient temperature
- Wire ampacity based on NEC Table 310.16, 75°C column for standard terminations
- Load assumed to be either continuous (3+ hours, requiring 125% sizing) or non-continuous based on user selection
- Existing circuit load assumed at zero unless user specifies current draw from other devices on the circuit
- Single-phase 120V or 240V circuits - does not evaluate three-phase or high-leg delta configurations
- Standard residential wiring assumed (copper conductors, NM-B cable in walls, THWN in conduit)
Limitations
- Does not verify actual wire gauge installed in the wall - user must confirm existing wire size
- Cannot detect shared neutrals, multi-wire branch circuits, or other wiring configurations that affect capacity
- Does not account for voltage drop on long runs which may reduce effective capacity
- Motor loads require special consideration (NEC Article 430) beyond simple ampacity comparison
- Does not evaluate panel bus rating, main breaker capacity, or service entrance limitations
- Existing circuit breaker condition and age are not factored into the assessment
References
- NEC (NFPA 70) Article 210 - Branch Circuits
- NEC Article 220 - Branch-Circuit, Feeder, and Service Load Calculations
- NEC Table 310.16 - Conductor Ampacities (75°C column)
- NEC 210.20(A) - Continuous and Noncontinuous Loads (125% rule)
- NEC 240.4 - Protection of Conductors (overcurrent protection requirements)
- UL 489 - Standard for Molded-Case Circuit Breakers