I'm a landlord and my property is in Northern San Diego County. We have received 7 bids from HVAC contractors for replacing the furnace and the ac (they're 30+ years old), and some recommend a 70 KBTU furnace and some recommend 90 KBTU. One contractor told me that either one is adequate (San Diego does not get very cold) but the 90K has the same size and cost as the 70K so he says I should go with the 90 because it will heat the house faster,.
Problem is, this page says that too many furnace BTUs causes energy loss and more wear and tear from excessive cycling on and off.
Also, my (admittedly non-professional) ****** research, along with one contractor telling me that our insulation is excellent, strongly indicates that 70K will be enough.
My question for the professionals is this: Assuming the contractor is correct, and either 70 or 90 will work, is it really better to go with the 70K furnace as the web page indicates, or is the difference really no big deal?
Thanks in advance for any help you can give.