All this computing power chews up electricity, and that costs money. It's worth looking at your hardware's energy consumption in watts, when making your choice. You want to make sure that you don't end up spending all of your money on electricity to mine coins that won't be worth what you paid.

Use these two factors to work out how many hashes you’re getting for every watt of electricity that you use. To do this, divide the hash count by the number of watts.

For example, if you have a 500 GH/sec device, and it’s taking 400 watts of power, then you’re getting 1.25 GH/sec per watt. You can check your power bill or use an electricity price calculator online to find out how much that means in hard cash.

However, there’s a caveat here. In some cases, you’ll be using your computer to run the mining hardware. Your computer has its own electricity draw on top of the mining hardware, and you’ll need to factor that into your calculation.