Many people mistaken the term "free energy" as energy that you can get for free. Well, that is wrong.
At least you need to buy the device that provide you with "free energy".
Then you may need to maintenance it or prepare budget to make it work continuously.
Then some of "free energy" device hide fact that they consume or get consumed. This is especially true for "run on water" solution. Not just it need expensive kind of water, it also has short runtime because the device electrode is consumed.
The durability is something the inventor rarely tell you. This also hide the actual cost of the energy when you need to replace it.
Even solar cell is not cheap. Just calculate the investment you need to get electricity for your house for two years and then compare it how many you currently spent. Why two years? this considering the fact that your may be clueless and may end up with short life cheapskate solution.
This is the same with hydro.
But the bottom line is, you can not get energy for free. Either you have to spent money to get it or at least to spent a lot of time to prevent being scammed.