Looking for some HVAC advice for a new furnace to heat 1500 sf of our house. Received four quotes from well-rated and regarded companies (Oasis, Shavitz, Elite, My Guy) and I'm confused how many BTUs I need for a new furnace. Two quoted me at 60,000 and one at 80,000 and haven't received the last quote. No one did a manual j load calculation. If I do a simple calculation of 1500 sf x 45 BTU (zone 3 climate), that's 67,500 BTU but two companies are quoting 60,000 with 95 or 96% efficiency. Does anyone have any advice here with how many BTU to go with and any recommendations for a HVAC company? Thanks!