It can make sense to combine stoves used for heating with peltier elements. When the heat is used at lower temperature than the combustion, you can get electric

It can make sense to combine stoves used for heating with peltier elements. When the heat is used at lower temperature than the combustion, you can get electricity on the exchange. So you run your boiler at 105% normal capacity and extract 5% electricity. This generates electricity at the price of gas. Of course, your boiler must have the extra capacity, and the additional components are an investment.