Enter values
Power - the rate of energy transfer. In solar systems, this is how much energy your panels produce or your devices consume.
Current - the flow of electrons through a circuit, measured in amps.
Volts result
Enter values to calculate
Enter watts and amps to see the volts result.
Understanding the Relationship
Key formulas
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:
- Understand current — Higher power at the same voltage means more amps
- 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
Verifying Panel Voltage from Specs
A 450W solar panel with an Imp of 11.72A operates at 38.4V Vmp. This confirms the panel's operating voltage from its wattage and current rating.
Determining Battery Bank Voltage
A 2,400W inverter load drawing 50A requires at least 48V on the DC bus — confirming you need a 48V battery bank, not 24V.
Confirming DC Appliance Compatibility
A 100W device drawing 8.33A needs 12V to operate, confirming a 12V battery system can power it directly.
When you'll need this conversion
- Choosing Battery Bank Voltage — If your maximum expected current draw is 60A and total load is 2,880W, you need at least 48V. This prevents excessive current that would require extremely thick cabling.
- Troubleshooting with a Clamp Meter — You measure 9A from a 350W-rated panel. Expected voltage should be about 38.9V. If your voltmeter shows only 28V, something is wrong — possibly shading, a bypass diode issue, or a bad connection.
- Checking Charge Controller Compatibility — If your charge controller needs 5V above battery voltage to begin charging and the panel produces 300W at 10A, the panel voltage is 30V. For a 24V battery, that is sufficient. For 48V, it is not.
Voltage Sag Under Load Is Real: A 48V battery bank may sag to 44V under heavy load. If you designed assuming 48V, your actual current draw will be higher than expected — same watts, lower volts means more amps.
Series Layouts Increase Voltage: Panels in a series layout add their voltages. Two 350W panels (each 37V Vmp) in series produce 74V at the same current, one way to reach a charge controller's input voltage.
Never Exceed Controller Max Input Voltage: MPPT controllers have a maximum voltage rating (often 100V or 150V). Cold temperatures raise Voc significantly — always calculate maximum expected Voc using temperature coefficients.
Solar calculators
Related conversion calculators
Last updated: January 3, 2026
