Bryant and Bosch Buderus gas boilers receive the highest recommendation in reviews from HVAC for Beginners, as of 2015. The Bryant Legacy Line BW1 and BW2 are the best recommended basic boilers, and the Bryant Preferred Series BW3 and Buderus Logamax Plus GB142 are the best recommended premium gas boilers.
The Bryant BW1 and BW2 units are made of cast iron with burners composed of stainless steel and titanium alloy. These units are 81.5 percent energy efficient with heating capacities ranging from 30,000 BTU to 226,000 BTU. The Bryant BW3 is 84.4 percent efficient with heating capacities ranging from 36,000 BTU to 186,000 BTU, and the BW3's heat exchanger carries a 20-year warranty.
The Buderus Logamax Plus GB142 is considered the ultimate boiler, according to HVAC for Beginners. This 95 percent efficient boiler is available in four different sizes with heating capacities ranging from 75,000 BTU to 199,000 BTU. The GB142 features modulating operation, has an aluminum heat exchanger and is compatible with an indirect domestic water heater.