The Q Premier Boiler combines a 132,000-Btu heating-only boiler and a 24-gallon charged indirect hot-water tank in one compact unit with roughly half the footprint of a conventional boiler and water heater. One potential problem with a combination boiler/hot-water heater is a mismatch between the heating and DHW loads, but Rinnai claims that this isn’t an issue with the Q Premier: You can size for the heating load yet still get 243 gallons of 107°F water during the first hour after a full charge, thanks to temperature stratification (heating the top of the tank first) and domestic priority (in which DHW takes precedence over heating). The boiler costs $8,475.

Rinnai, 800/621-9419,