The 3, 5, and 7 kW capacity SunPumps are considered a home’s primary source of heat when right-sized, and come with full electric hybrid back up booster in the storage tank. You will require an Auxiliary heat source for the 10 and 14 kW sized SunPumps because the 6 kW booster will not cover the full load of these larger heat pumps. In new construction, consider having an alternate fuel source like a propane or wood fireplace for backup during cold snaps. Older homes can often keep the original boiler or furnace as the backup, rather than removing the old system. Customers tell us they love having the backup even if it is rarely used, it is better to have it.