I have just talked to a couple of companies regarding whole house generators and was told by both that to install a natural gas generator (that will run everything, except the AC) would cost around $5500. And to install a natural gas generator (that will run EVERYTHING) would cost approx. $8500.
But in the mean time, I'm running all hydrosponges in the tanks and recently just switched over to a ventless N.G. 30,000btu heater. So if I loose power, the heater ignition is battery powered and it keeps running like normal and I'm using a linear piston pump to supply air to everything. All I have to do is run an extension cord into my basement for the air pump and to my well and I'm still in business.