Please contact us directly for pricing information on the units not listed with price. Certain brands are only sold within a 50 mile radius of us. Central Vacuum Power Units, factors other than air watts should be considered: Altitude, the amount of hours of daily usage, complexity of plumbing installation, length of furthest inlet, noise level desired, type & size of filtration, construction, materials, and budget. Square footage for all the units we sell are based upon the unit itself without taking the other considerations into account. Air watts = Water lift X CFM divided by 8.5.