While there is a formula for it, thankfully it does not require you to be a mathematician. All you need is a calculator...or your phone because it probably has a calculator on it.
Of course you will also need the item(s) you are wanting to power. For larger items, you will need access to the panel where the electrical information is stored. This is generally on the bottom or the back and you shouldn't have to disassemble anything to get to it (hopefully).
In the example to the right, it tells us the volts "V" and the amps "A" for this particular device.
The formula for finding out the Watts is Volts times the Amps. So our formula and outcome are seen here based on the device pictured above.
Now that we know the Watts, we just need to figure out which unit is right for us. This is simply taking the watts of the unit we are looking to purchase and dividing that wattage by the wattage of our device. Our device has 30 watts.
You can see the chart to the right with the options we have available. Goal Zero power packs are easy to figure out because their wattage is on the product description.
The Sherpa 50 has 50 watts, Escape 150 has 150 watts, etc.
Looking at the chart to the right, we can run our office air purifier for up to 41 hours using the Yeti. Of course, that is assuming that we would only be running our air purifier and nothing else. if you are using multiple devices, you can simply add them together to get the total watt hours.
How to choose solar power kits powered by Goal Zero.