i did think of wired as it has the option but couldnt get a cable up too much hassle. my siren has the leds activated so that will have a little drain but not too much. they should have added a small solar pannel like the old responce sirens had to keep the battery charged. but then again they wouldnt sell many replacement batterys.It depends how many times it goes off but 2 years would be my advice. I've got wired bells on mine so they are lit up at night.