There is a nice business, making the kits. Google thermoelectric mains generator Hyundai DHY6000SE Diesel Generator
We only need add a 50x1cm steam plasma tube – filled with steam from a paint stipper – to 4 atmospheres – or vent the steam from a pressure cooker,
The tube will generate 1.2MW of heat. We draw in air, to get hot air at 350oC. We can get higher temperator thermoelectric crystals. But standard one runs up to 350oC.
So we get 60kW of power – enough for our own use, and we sell 52kW to the grid – 136,000 UK pounds every years.
From 5x10-20cc of regular water a year. So we generate all our power, and pass the exit heat to our central heating boiler. Though maybe we would prefer to vent 95% of the heat.
And this is why British Gas is making all the cash it can. As developing a working system will take 2 months. And we sell the kits for 1,500 UK pounds – so sell it with finance. 4 years of 500 UK pounds.