For how long…and how many watts is the heater?
These stations aren’t great with heaters, they are high wattage draw devices and kill battery life.
Unless it’s a small tank with a small heater. That’s ok
Most normal outages are a few hours. Or less than 24. Most “emergency” outages from a major weather event are a few days to a week or more
If your worried about powering the tank for 3+ days on battery then you will want a generator
If you want the tank to survive for roughly 24 hours, automatically, until power is restored, then you only need to focus on one key area - flow.
Lighting, skimmer, roller mat, all those things can be offline for a day and you won’t have any issue.
I would focus on getting an efficient dc return pump (if you have a sump) or a dc wavemaker and just have that one item on backup power.