Looking to run a backup server for pfsense

Right now I am running an pfsense router on a custom build CPU which is running perfect, but the problem is there are frequent power outages , I have an UPS but it does not last for more time. So , I am thinking to make an backup server on an thin client which uses less power and can come in action if anything goes wrong with the main router.

So is there any way I can make a backup router for my main router??

You might find a BIOS setting that allows the previous state to be recovered.

You need to have the same hardware and you could set HA - High Availability | pfSense Documentation (netgate.com)

Another option, for any reason the pfsense does not start have the PFSense iso image available and a good backup to reinstall.