I'm getting quotes to install a new furnace and one brand that I like does not have a unit that meets the 95% efficiency to take advantage of the tax credit. The contractor has suggested to install a larger unit (90,000 btu's rather than the 75,000 btu unit) to get higher efficiency and meet the IRS rules for the tax credit. I questioned him about this since I'ver heard to not oversize. He did, to his credit, note that it is not good to oversize but with multi-stage units it is not as critical with single stage units. His rational is as follows: since the unit is a multi-stage furnace, it would start at the low setting (70% of max output) and run until the house heats up. In other words, the two units would operate the same the majority of the time. When the demand is higher it would start at max output and heat the house more quickly than the lower efficiency unit. This makes sense to me but I'm still not totally convinced this is the correct thing to do. I save some money with the tax credit (it more than offsets the cost of the higher efficincy furnance) and I save a few dollars on my heating bill. Any comments????