Can unit still start if we lose electricity- back up battery start?

Yes, it looks like you can use this in case if power outage. Please see page 9 of the Installation Manual which states: "*NOTICE: This heater is intended for use as supplemental heat. Use this heater along with your primary heating system. Do not install this heater as your primary heat source. Do not run ceiling fan while heater is running. In the event of a power outage, you can use this heater as your primary heat source." Please also see the manual for any other information regarding how this unit works and is to be installed in your home. If you have any further questions, please call us and we will be happy to assist you.