Mainly solar thermal. Looks like the Dover house stored heat in tanks of melted salt. They leaked and after three years the salt and water stratified and refused to remix so it stopped working... Clever attempt though.
https://www.technologyreview.com/s/419445/the-house-of-the-d... When you hear that 30% of Pasadena houses had solar water heaters by 1900 it often seems as if we are just recreating the same stuff repeatedly. Hobbyists today seem to be doing much the same as people in the 70's oil shock. Only big change seems to be vacuum tubes (and PV I guess).