localStorage.power_status = document.getElementById('power_status').checked;

var pwr_s = localStorage.power_status;

    chrome.storage.sync.set({'power_s':pwr_s}, function() {
        console.log('Option power set: ' + pwr_s);
    });

chrome.storage.sync.get('power_s', function(r) {
    console.log('Status: ' + r['power_s']);
});