How to Determine Watts, Voltage & Amps in Shop Equipment

An appliance nameplate

You'll need to calculate your workshop energy demand when installing or upgrading an electrical subpanel or when choosing a generator for a backup supply source. It's also good to know when estimating the cost of your electricity bill. The most important number you need is the wattage, or total power. Wattage is the product of the voltage, or electrical pressure, multiplied by the amps, or electrical current. Follow the steps below to get the correct numbers.

Things You'll Need

• Calculator

Instructions

1. Find a plate or tag on the back or bottom of your equipment that resembles the one shown in the picture above. This plate lists how many amps and volts your equipment uses, and it may also list the wattage.

2. Consult your owner's manuals if you cannot find a nameplate on your equipment. If you do not have the manuals, consult the manufacturer's website or contact your equipment dealer for the information.

3. Calculate wattage if the figure is not supplied by multiplying the volts by the amps. The volts will always be either 120 or 240.

4. Remember when calculating demand for a generator or a subpanel that you won't be using all your equipment at the same time---you only need enough electricity to supply whatever is running at any given moment. Knowing which tools are your biggest energy users allows you to calculate the maximum amount of energy you could possibly need. For example, you may typically run a heater, some lights and a table saw at the same time---if the heater and table saw are the biggest energy users in your shop, then their energy needs combined with the lighting needs represent the maximum amount of electricity that the shop needs. Multiply that figure by 1.25 to avoid any problems with overloads.

Resources

• Using Watts to Calculate an Electrical Bill