You are assessing your power needs for keeping the lights on during a power outage. You haven’t fully decided on a solar generator, power station, or some smart combo. Like a boss, you read our beginning guides so you know how to size up your power station (in case you missed it, here’s the link).

Armed with the knowledge that your first step is to add up the watts of all the critical devices you wish to power, you pull your freezer back from the wall (why the heck is the label always at an awkward place in the back?), swish through the dust bunnies, and finally end up on your hands and knees to read the label.

Guess what. There is no watt rating. You scrub the grime off the label with your thumb (how do the backs of freezers get so dirty?). The information you see is 127 V and 1.4 A. You unfold yourself and stand upright, swiping at the dust on your clothes while muttering to yourself because instead of the info you sought, you only found a mouse hole in the baseboard.

So off you go to Home Depot to get steel wool (to plug the hole), masonry lath (to cut and staple over the hole), and a new attitude (unfortunately, those are out of stock but looking at a new grill does the trick).

Formula for Volts and Amps

How do you figure out the watts if the label of your appliance doesn’t list it?

It’s actually fairly easy once you know how. I’ll give you the formula and then explain it later, but I fully expect you to not finish reading once you get it. Unlike most recipe websites, we care about your time so here it is:

Watts = Volts × Amps

Yeah, it’s that easy. So in this case, you take 127 volts × 1.4 amps, giving you 178 W.
Using that formula lets you know that you need 178 Wh to keep that freezer running for an hour. However, freezers typically run only about a third of the hour (and that's a generous estimate), which equals around 59 W average.

You decide to play it safe and round up to 60 W. Now multiply 60 W times the number of hours you want your power station to run it.

Formula for Kilowatt-Hours

But what if the label only lists kilowatt-hours per year?

This is a common boasting point on many energy-efficient appliances nowadays. How do you determine wattage from that?

Let’s say we are shopping for a freezer and see a tag that says this freezer uses 227 kWh per year. Here are the steps to determine average wattage:

• Divide 227 kWh by 365 days = 0.622 kWh/day
  
• Take your daily 0.622 × 1000 to convert to watt-hours (good ol' metric system) = 622 watt-hours/day
  
• Finally, divide 622 watt-hours per day by 24 hours and your wattage is 25.9 W on average

Now, again, to determine the size needed for your power station, multiply the 25.9 W by the number of hours you want it to run. Because we determined the average watts per hour, you don’t need to factor in the off/run time anymore. If you want to power it for 4 hours, you would need a power station that has at least 125 Wh.

Conclusion

Now that you have this knowledge, you can determine the wattage and watt hours of pretty much any device or appliance you want to power. 

Again, repetition breeds mastery so lets list the formulas again.

Watts = Volts × Amps
Watts = (kWh × 1000) ÷ Hours

If you have questions or need a bit of guidance when choosing your power station, feel free to hit that chat button or shoot us an email. We would love to chat with you and help empower your power station search.