After the first 20 minutes, the water temperature seemed to increase at a fairly constant rate of 0.0006 degrees Celsius per second. This increase in temperature means there is an increase in thermal energy, which we can calculate as:

Here m is the mass of the stuff (in this case, water), and C is the specific heat capacity—the amount of heat energy required to raise the temperature of that substance by 1 degree Celsius. for water, C is 4.186 joules per gram per degree Celsius. So, with 1000ml of water and my rate of temperature change, I get that the water requires a power of 2.51 joules every second (or 2.51 watts).

Oh look at that. Even with this rudimentary measurement system, it’s pretty close to the power going into the Raspberry Pi. The difference is probably due to imperfect insulation. So you can see that the cryptocurrency power is just thermal energy. Honestly, I’m surprised it worked so well.

Show me the money!

While it’s possible to run a crypto miner as a way to heat your house, that’s probably not why people do it. What is the payout? Well, let’s do some quick calculations. I ran my Raspberry Pi miner for 12 hours. How much money did it make? Wait for it… 0.00000006 XMR. To convert it to US dollars, it is 0.0012 cents (not dollars). Yes, it will be a slow way to amass a fortune. If I ran it for 12,000 hours, I still couldn’t buy a piece of gum. Probably not even using gum.

And that’s not even accounting for the cost. I mean, mining isn’t free—you have to pay for the electricity. The average cost of electricity in the US is 16.94 cents per kilowatt hour. If I run my miner at 3 watts for 12 hours, that would be 24 watt-hours, or 0.024 KWh. Using the price of electricity, it would cost 0.41 cents. Let me just do some quick math here. Yes, 0.41 cents is more than the money I created. I’m no financial expert, but that seems like a bad business model.

Of course, no one but a physicist would mine crypto on a Raspberry Pi. There are fancy mining machines (costing thousands of dollars) that allow you to mine coins faster and with less energy. The other thing to consider is the future price of a cryptocurrency. Even if the cost exceeds the reward today, it may one day be worth much more. Finally, a crypto miner can be in a location with cheaper electricity. It is even possible to run a miner on solar power.

However, don’t forget that for every joule of energy you put into a miner, you’re going to produce 1 joule of thermal energy. You need to get rid of that heat or it will cause problems for your computers. But cooling systems use more energy, and this can make it difficult to produce profitable currency.

But it must work because there is quite a bit of mining in the US. In 2024, it was estimated that 2.3 percent of electrical energy went into cryptocurrency. It’s quite a bit, and I’m really not sure it’s the best use of our energy supply – especially since crypto is just a made up thing.