During the time I’ve been involved in the North American hydronics industry, there have been significant improvements in the thermal efficiency of hydronic heat sources. The 1960s vintage ranch house that I grew up in is a good example.
When built, it was fitted with a baseboard heating system supplied by an oil-fired steel fire tube boiler. The boiler was equipped with a tankless coil for domestic water heating. A Honeywell round thermostat controlled the entire 1,500-square-foot house as a single zone.