Generac Residential Generators Product Support Brochure Contact Sales Rep A permanently installed Generac home backup generator protects your home automatically. It runs on natural gas or liquid propane (LP) fuel, and sits outside just like a central air conditioning unit. A home backup generator delivers power directly to your home's electrical system, backing up your entire home or just the most essential items. Available from 6kW to 20kW.   All 2 day and overnight orders must be placed no later than 1:00 PM EST. Otherwise, order will be shipped the following business day.