@bikepedantic This sounds like a job for a heat pump.
@Will Agree, and we're planning to get them, but this boiler/tankless water heater are only 4 years old, we were just anticipating supplementing. And we're mid-project on trying to upgrade panels (there's a national panel/meter shortage)
@bikepedantic Time to install the Florida-style outdoor shower and enjoy the brisk contrast between near boiling water and single digit outdoor temps. Invigorate your morning routine.