[dhs12345]

Passive energy doesn’t generate electricity. It uses the heat energy to heat the house and provide hot water.

[Yosemitest]

I had a friend at Plattsburgh AFB NY that supplemented his home with 55 gallon steel barrels filled with water and painted black, that absorbed heat on his enclosed southern porch.
He'd open the front door into his house at night and let the heat flow through the house assisted by ceiling fans.
It helped a little, but made his enclosed porch unbearable to walk through.

[Prophet2520]

“My dad claims that it never paid for itself but I skeptical. All of their hot water needs were covered “

NO, NO, NO. That is not passive solar. That is solar hot water. It is expensive. It is theoretically possible to make a completely passive solar hot water set up, but it is seldom done because the heat exchange is so poor.

There are do it yourself ways to do solar hot water which can be more cost effective, but they tend to be “red-neck” :-) or less professional.