Amps, volts, and watts decide whether your actuator system gets enough power or cooks the wiring. Voltage is electrical pressure. Amps are current flow. Watts are power. For DC actuator systems, the first sizing check is simple: watts = volts × amps.
"The mistake I see most often is sizing a power supply from the free-running current on a spec sheet. The actuator only pulls that current with no load on it. Once you add real load, friction, and the startup spike, the supply has to deliver well above that number — or it shuts down mid-stroke." — Robbie Dickson, FIRGELLI Automations founder and former Rolls-Royce, BMW, and Ford engineer
What are amps, volts, and watts?
<<Volts push current through the circuit. Amps measure how much current flows. Watts measure electrical power.
What is the simple explanation?
A 12V actuator pulling 10A uses 120W while it runs. If the load increases and current rises, power rises too.
Use the formula below to calculate actuator power.
Watts = volts × amps
What should the calculator inputs be?
Use this as a first-pass sizing tool. Then confirm the final choice against the actual FIRGELLI product page, the wiring diagram, and your real mounting geometry.
How do you use this calculator?
- Enter the real project values, not guesses from a different mechanism.
- Use measured current, load, stroke, voltage, or signal values where you can.
- Add margin for real brackets, wiring, friction, and installation conditions.
- Click Calculate to see your result.
How should you size actuator power?
Match voltage first. A 12V actuator needs a 12V DC supply. Then size current for the highest current the system may see, especially if multiple actuators run together.
Do not size the power supply from free-running current only. A loaded actuator pulls more current, and startup current can jump above normal running current.
What is a simple example?
2 actuators each pull 8A on a 12V system. Total current = 8 × 2 = 16A.
Watts = 12 × 16 = 192W. With 1.25x margin, power supply target = 20A, or 240W.
Recommended FIRGELLI setup
Which FIRGELLI products fit this job?
Choose power supplies from voltage, total current, margin, and installation environment.
AC to DC Power Supply 12V 30A
Use this when the project plugs into wall power and needs a 12V DC supply with high current capacity.
View 12V 30A Power Supply
Water Resistant 12V 30A Power Supply
Use this when the power supply location needs a water-resistant 12V 30A option.
View Water Resistant Supply
DC Power Adaptor 12V
Use this for smaller 12V actuator projects where the current demand fits the adaptor rating.
View DC Power AdaptorFor controls, match the current rating of the switches, relays, or motor driver to the actuator system.
What are common mistakes when using this calculator?
- Using free-running current instead of loaded current. The current on a spec sheet with no load is the lowest the actuator will ever pull. Use the loaded current, or measured current from your real mechanism.
- Ignoring startup current. Actuators draw a brief spike well above running current at startup. A supply sized exactly to running current can trip or shut down on that spike.
- Forgetting simultaneous actuators. If two or more actuators may run together, add their currents. A supply sized for one actuator will brown out when both move.
- Ignoring voltage drop on long wire runs. The supply may deliver 12V at its terminals but the actuator sees less under load. The calculator does not include wire losses — size wire separately.
- Skipping the margin. Sizing the supply at exactly running current leaves no room for friction, temperature, or load variation. 1.25x to 1.5x is the practical starting point.
How can you verify the calculator output is reasonable?
- Cross-check against the actuator product page. The current on the product page under rated load should match or exceed the value you entered. If you entered a lower number, recalculate.
- Measure current under real load. Put a clamp meter on the supply lead while the actuator drives the actual mechanism. If measured current exceeds your input value, resize.
- Check voltage at the actuator terminals under load. If the actuator terminals read significantly below the supply voltage during travel, voltage drop is real — use heavier wire or a shorter run.
- Confirm the supply does not overheat or shut down during repeated cycles. A supply at its limit will get hot or trip. If that happens, the calculator output was undersized.
- Run a full-stroke test under worst-case load. The end of travel and the start of travel are where current peaks. If the supply holds voltage at those points, the sizing is real.
