Have a 12vdc battery on standby in case of an ac outage.  My 50 watt 144mc transceiver runs just as good on a battery as it does an ac supply. You are going to be listening most of the time and the receiver drain is small as compared to transmit. If you have a volt meter handy, clip it on the battery terminals and watch the battery voltage. A 50 watt output in transmit will draw 5 to 6 amps during transmit and probably .5 amps receive.  

  If you thinking about getting a dedicated battery for this use, buy a gel cell battery.  No acid, no fumes, hold the charge and no voltage decay from lack of use. Another comment, this solid state equipment likes to see a good DC power source that is well filtered and has very little AC ripple component in the DC output.

  Bob   W8LXJ amateur radio