WireGaugeCalc Free calculator · NEC cited · works offline
NEC Solar DC Wire
NEC solar dc wire is quick to size with WireGaugeCalc, which sizes PV string conductors from the array current.
You enter the short-circuit current, voltage, and run length, so the tool applies the PV factors and returns the conductor and voltage drop.
That helps you set the DC home run from the modules to the inverter without guesswork.
Open the calculatorEnter any two values and read the rest.
Ohm’s law: V = I × R and P = V × I. Field aid only, verify against the current NEC and your local authority having jurisdiction.
How The PV Source Circuit Current Is Built Up
NEC 690.8 has you take the module short-circuit current, multiply by 125 percent for continuous duty, and then by another 125 percent for the maximum-current rule.
That combined factor of 156 percent sets the conductor ampacity floor, so DC solar wire is usually larger than the bare module current suggests.
On long DC home runs the voltage drop matters too, so the calculator checks both the ampacity floor and the drop across the run.
What The Solar DC Wire Sizing Uses
Enter the array details and the tool sizes the run:
- Module short-circuit current, Isc
- The 156 percent combined PV factor from NEC 690.8
- DC system voltage of the string
- One-way run length for the home run
- Conductor size and voltage drop across the DC run
One app for every NEC calculation
WireGaugeCalc keeps the calculations you reach for most in one place:
- Voltage drop and wire sizing for any run
- Conduit fill for EMT, PVC, and RMC
- Box fill and junction box sizing
- Ampacity and temperature derating
- Motor circuit and load calculations
- Conduit bend offsets and saddles
Built for the field, works offline
The whole app runs on your phone, so it keeps working in a basement, an attic, or a job site with no signal.
There is no account to create and nothing to load. Open it, run the number, and get back to work.
- No signup and no signal needed
- Answers in a tap, not a spreadsheet
- Same tool on phone, tablet, and desktop
Every result cites the NEC article
Each answer shows the table or formula it came from, so you can check the method and learn the code as you go.
That makes the app useful on the job and during exam prep, since the reasoning is right next to the number.
Switch the code year your job runs on
Jurisdictions adopt the NEC at different times, so you can match the calculation to the code in force:
- NEC 2017, 2020, and 2023 tables
- Copper and aluminum conductors
- 60, 75, and 90 degree C terminations
- Single-phase and three-phase systems
Run the number, then get back to work
Stop flipping through a paper book or hopping between calculator sites. Enter your values, read the code-cited answer, and move on. Free to use, no signup.
Open the calculatorFrequently asked questions
Why is solar DC wire sized at 156 percent of the module current?
NEC 690.8 applies a 125 percent continuous factor and a 125 percent maximum-current factor, which multiply to about 156 percent of the short-circuit current. The conductor ampacity must meet that value.
Do I need to worry about voltage drop on DC home runs?
Yes, long DC runs from the array to the inverter can lose voltage and harvest, so many installers hold the DC drop near 2 percent. Verify the result against the current NEC and your local authority having jurisdiction.
Is WireGaugeCalc free to use?
Yes. Every calculator is free to run with no signup. A paid tier adds saved projects, PDF reports, and extra code years, but the core math stays free.
Does it work without internet?
Yes. The app runs on your device, so it keeps working with no signal on a job site, in a basement, or in an attic.
Are the results code accurate?
Results follow published NEC tables and standard formulas, and each answer shows the article it came from. It is a field aid, not a stamp of approval, so verify against the current code and your local authority before you wire anything.
Which NEC code year does it use?
You can switch between NEC 2017, 2020, and 2023, since jurisdictions adopt the code at different times. Pick the year your job runs on.