GREAT PRODUCT. GREAT PEOPLE. SAVED OVER $2,000 ON HEATING THE FIRST YEAR, We hired Tankless Concepts to replace our oil-fired heating boiler and gas-fired tank-style hot water heater with a gas-fired NAVIEN combination boiler and tankless hot water heater, after meeting with four contractors and reviewing three proposals. We saved over $2,000 on our heating costs the first year. The old system used four zones to unevenly heat our 80-year old; 2,300 square foot; 4-bedroom; 3-1/2 baths; house. The new two-zone system, developed from a room-by-room heating analysis of our existing radiators and cast iron baseboards, heats the house evenly. The hot water is endless. As a retired engineer, I was impressed by their detailed technical and product knowledge. They understood and answered all my questions. They developed innovative low-impact cost-effective boiler venting solutions for this old brick colonial. The installation started, proceeded, and completed on the planned schedule and at the agreed cost. There were no surprises. We are reaping substantial savings. With the old equipment, our monthly non-electric energy costs were about $230 a month ($2,760 a year) for the oil-fired boiler and about $25 a month ($300 a year) for gas-fired hot water, cooking, and clothes drying. With the new equipment, we heated the house through the entire 2019-20 heating season for about $600.