When you need this conversion
Volts to watts conversion is the starting point for sizing almost anything electrical: matching a solar panel's voltage and current to an inverter, checking whether a battery and load are compatible, or verifying an appliance's power draw from its voltage and current rating. It is also how manufacturers derive the wattage figure printed on panel and appliance labels.
The formula explained
Power in watts equals voltage multiplied by current, adjusted by power factor for AC loads:
Watts = Volts × Amps × Power Factor
For DC systems, including solar panels, batteries, and most electronics running off a DC bus, power factor is always 1, so watts is simply volts times amps. For AC loads, power factor accounts for the phase shift between voltage and current; resistive loads like heaters sit at 1, while motors and electronics typically run between 0.8 and 0.95.
Common values at a glance
| Volts | Amps | Watts (PF 1) |
|---|---|---|
| 12 V | 10 A | 120 W |
| 24 V | 10 A | 240 W |
| 120 V | 10 A | 1200 W |
| 230 V | 10 A | 2300 W |
| 48 V | 20 A | 960 W |
Practical tips
- Solar panel datasheets list voltage and current at maximum power (Vmp and Imp); multiply these two figures, not the open-circuit voltage and short-circuit current, to get the panel's true rated wattage.
- Battery bank voltage (12V, 24V, or 48V) combined with your inverter's maximum continuous current tells you the largest wattage the pair can safely deliver.
- For AC loads, use the real power factor whenever it is known; assuming PF equals 1 on a motor-driven appliance will overstate the actual wattage delivered.
- Voltage sags under heavy load, particularly on long DC cable runs, so measure at the load if precision matters rather than relying on the source's nominal voltage alone.