Enter both values to calculate amps
Volts (V)
Common:
Watts (W)
Amps (A)
Result will appear here
Understanding the Relationship
The relationship between watts, volts, and amps follows the Power Formula:
- Power (P) = Voltage (V) × Current (I)
- Voltage (V) = Power (P) ÷ Current (I)
- Current (I) = Power (P) ÷ Voltage (V)
In Solar Systems
Understanding these relationships helps you:
- Size your wiring - Higher amps need thicker wires
- Choose inverters - Match wattage to your needs
- Configure battery banks - 12V, 24V, or 48V systems affect current flow
- Calculate loads - Know how much power your devices draw
Real-World Solar Examples
350W Panel Operating Current
A 350W solar panel at 37V Vmp produces 9.46A. This current value determines what wire gauge you need from the panel to the combiner box or charge controller.
5,000W Inverter DC Current
A 5,000W inverter on a 48V battery bank draws 104.17A at full load. This requires 2/0 AWG or larger copper cable and a 125A or larger DC breaker.
DC vs AC Current Comparison
A 240W refrigerator on a 120V AC circuit draws 2A. But on the DC side of a 12V system, the same 240W draws 20A — ten times more current.
When You'll Need This Conversion
- Sizing Battery-to-Inverter Cabling — A 3,600W inverter on a 24V system draws 150A. NEC requires 125% oversizing for continuous loads, so cable and breaker must handle 187.5A. This is one of the most critical calculations in any off-grid system.
- Determining String Fuse Ratings — Each 400W panel produces 10.81A at Vmp. The Isc is about 11.5A. NEC 690.8 requires fuse rating at Isc × 1.56 = ~18A. Knowing current per string is essential for overcurrent protection.
- Sizing a Charge Controller — With 1,800W of solar on a 24V battery system, you get 75A of charging current. You would need an 80A or 100A MPPT controller — or split the array across two smaller controllers.
Solar Tips & Common Mistakes
DC-Side Current Is Much Higher Than AC: A 1,500W load is only 12.5A at 120V AC, but 125A at 12V DC. Undersizing DC cables because you are thinking in AC terms is a fire hazard.
Use Isc for Fuse Sizing, Not Calculated Imp: Isc is 5–10% higher than Imp and represents the maximum possible panel current. NEC requires overcurrent protection based on Isc × 1.25 × 1.25 = Isc × 1.56.
MPPT Controllers Change the Current Ratio: An MPPT controller takes high-voltage, low-current input and converts it to low-voltage, high-current output. If your array outputs 10A at 74V, the controller might output ~15A at 48V. Always calculate amps on both sides.
Solar Calculators
Related Conversion Calculators
Last updated: January 3, 2026
