The best power option for a smoke detector is a hard wired or AC powered dual sensor that has a battery backup. These models can be expensive to purchase and install so if you can’t afford a smoke detector like this you’ll have to compromise.
AC or hard wired smoke detectors can be powered by the existing electrical current in your home. They don’t need batteries to function but will be limited if there is a power failure. They also can be wired collectively so every alarm goes off at the same time if there is a fire.
Battery powered versions are relatively cheap and provide excellent protection. If the batteries are running low they will emit an audible chirp to let you know. Be sure to choose a brand that has been tested by an independent laboratory with batteries that can easily be changed.