Any of these portable power stations are great options to provide you with power when you need it -- it ultimately comes down to the power output you need, how many and which ports you prefer, and what price you're willing to spend. 

Even less expensive power stations are still an investment, both in money and in the physical space they take up, so you need to be sure that you're buying something that works for you. This means juggling a number of factors.

• Weight: Bigger isn't always better here. Is the portable power station going to be wheeled from room to room are you going to be moving it from your vehicle to your camp? Do you want something that you cold carry in a backpack for a day? 
• Battery capacity: If you plan of powering a home from your power station then you want as much battery capacity as you can afford, but for off-grid adventures it's important to bear in mind that there's a penalty here that comes in the form of weight.
• Cost: Some of units cost several thousand dollars, while others are a couple of hundred. 
• Charging: How do you plan on charging your power station? Are you mostly going to be using AC power from an outlet or do you want the independence of solar?
• Battery Chemistry: Lithium-ion (Li-ion) is the traditional battery technology, but the newer lithium iron phosphate batteries (LiFePO4) are safer and have a much longer lifespan.
• Warranty: Portable power stations are expensive, so I want manufactures to back their products with multi-year warranties. 
• Safety: Every unit I've tested has been subjected to numerous tests, from running for extended periods to check thermal management, to overloading them to see how they handle loads that are too much for them. 

At the core of this list is a lot of extensive testing of dozens of power stations. I regularly undertake trips that see me off-grid, either for camping or to carry out photography, videography, and drone work, and at these times, I rely on having access to a reliable power source. This is a great opportunity to test power stations under real-world conditions.

I also test them at home, both using them to run household appliances, and carry out testing on battery capacity, charge and discharge times, and how they handle overloading.

Finally, every unit is safety tested to make sure that it is safe for prolonged, heavy use.

Finding a balance between affordability and quality in power stations can be challenging, especially with some models priced significantly above$500. However, setting a budget around the$500 mark is a reasonable starting point for those looking to invest in a portable power station without stretching their finances too thin.

Some of these power stations are brought down below that$500 mark thanks to deals -- but be aware that these deals come and go, so if you're interested in a particular power station, grab it sooner rather than later.

Manufacturers typically offer different runtimes for things like lamps, refrigerators, CPAP machines and so on, but if you want to work this out for yourself you can need two figures. 

First, you need the power rating of the device you plan on running, which can usually be found on a label on the device, and is measured in Watts (W). You also need to know the capacity of the power station, measured in Watt hours (Wh), which should be printed somewhere on the device. 

Let's say you have a device that consumes 300W and a power station that has a capacity of 768Wh, you can get a ballpark runtime for the device using the following equation:

(768 x 0.85)/300 = 2.2 hours

Note that the capacity of the power station is multiplied by 0.85 to account for efficiency losses.

Four main things separate portable power stations and power banks:

• Capacity: While power banks are perfect for topping up a smartphone or tablet, a power station can be used to charge up devices multiple times because of the vastly bigger battery capacity.
• Size and weight: Power banks are something you can normally slip into a pocket, while power stations are things you lug about or wheel about from room to room.
• Outlets: While power banks feature USB ports, most power stations also have AC outlets for powering powered devices.
• Charging: While power banks are normally charged using a USB charger, power stations can be charged from a number of sources, such as main power, solar, and vehicle 12V outlets.  

The sub-$500 power station market is quite small, but there are some good deals out there, and along with the main list above, I've got a few alternatives that are worth considering.