Like it or not EU countries and Japan has been at the forefront on high efficiency home heating size units for decades. They also have been building either higher efficiency buildings (EU states) or smaller dwelling units (Japan) Look at the mini split market, its all Japanese developed tech that is now being copied by third world manufacturers. There are several of the Euro brands that make super energy efficient heating that are unknown in the US. US manufactures still build legacy heat pumps to support installations they have sold for decades and there are some geothermal manufacturers nibbling at the air to water market but not a big roll out yet. The problem is in most cases these do not retrofit well into a typical US inefficient ducted system. The temps are lower than standard heat sources and that means more warm air has to move around the house and far less tolerant of leaky duct running through unconditioned spaces. If you look at John Siegnethaler's column's, they almost all are based on low temp radiant emitters or properly designed radiant floor wall or ceiling systems that use very low supply temps. These cost money to install and not easy to retrofit. He uses local air terminal units for cooling, so instead of ducts he is using insulated cold water lines to move the cooling around.
Ideally TACO does the hydronic end of the unit inside the house and the German (or Japanese) equipment supplies it hot or cold water from the outdoor unit. BTW a typical northeastern home will have a 100,000 btu boiler as a base heating unit, the spec sheet shows 17,880 btus at 5 degree F. They have a backup resistive element on the buffer tank but that is not a lot of heat for a typical home in cold weather. IMO better have a backup for an area with consistently lower winter temps. Its good fit for Passive Homes and Zero Net energy that can ride through a cold spell but even in my fairly tight 30 year old home I would need a backup. Someone in in CT or south it may be great fit.
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