Electricity bill

Check what you're earning vs. what you're earning. In a lot of countries where electricity is not so cheap, such as certain parts of the U.S. you'll come close to earning a profit, or just barely earning one.

Just run a test, for a day or two and see exactly how much you earn, and if you can, use an online calculator with the wattage of your PC (total of Motherboard, CPU, Power Supply, and most importantly GPU's), and see how much electricity you've been used.
Once you've got that, find out how much it costs, but taking the wattage use and multiplying it by the cost.
Subtract that from what you earned, and if you're in the positive, then you'll make money if things continue as they are right now (because Crypto is unpredictable really). If you're in the negative, stop doing what you're doing and look for currencies that use less power (yes, the difference in algorithms can mean a difference in power usage), try underclocking (if you can), and if all that fails.... Then you won't be able to mine.