Source: Susquehanna

Cryptocurrency mining isn't what it used to be.

Last year, the "mining" process of earning new cryptocurrencies using high-powered computers, then selling those digital assets, became a profitable side business for savvy entrepreneurs who set up the mining rigs in their basements and dorm rooms.

But that side-hustle is no longer profitable if you're mining for the cryptocurrency ethereum using kits containing GPUs (graphics processing units). The profit per month is down for mining from about $150 last summer, to an estimated $0 for November of this year, according to analysis by Susquehanna.

In mining, machines run 24 hours a day, competing against other computers around the world to solve complex math problems. The first computer, or multiple computers, to solve the problem earns a fixed amount of bitcoin or ethereum.

The "hashrate," or speed at which a computer can complete that operation fell drastically for ethereum this year. A higher hashrate is better for miners and adds to the opportunity of finding the next "block" and therefore getting the reward of new cryptocurrency.

The value of ethereum meanwhile has dropped more than 70 percent this year, trading near $205 Tuesday, according to data from CoinDesk.

The combination of those factors means that mining ethereum using a GPU, Nvidia's flagship graphics card, is "no longer profitable," Susquehanna semiconductor analyst Christopher Rolland said in a note to clients Tuesday.