Yes, but it's important to understand how and when you'd use it for heating/cooling.
Heating and cooling are very energy-intensive: a ~1,500W AC could drain a 3kWh Complete system in about 2 hours, versus an efficient fridge using that same energy supply for 60 hours (!). For reference, an 10,000 BTU air conditioner is going to run between 800-1200 continuous watts. Running AC intermittently on its lowest setting, using a fan to circulate air, or using a small space heater or electric blanket are all ways to help make the most of your energy reserve.
That said, sometimes just a few hours can be critically helpful, and a great way to leverage Time of Use scheduler inside Backup: many utilities charge more during peak hours and less during lower energy demand hours. Running your AC off of Backup during peak demand and recharging at cheaper times can be a way to save on your electricity bill while also helping to take pressure off the grid. You can schedule this behavior directly in the free app and change it at any time. Exact savings are subject to your local utility program and rates.