<select multiple="multiple" name="price[]" id="sel_1">
    <option value="0"></option>
    <option value="10">2015</option>
    <option value="15">2016</option>
</select>
<span id="usertotal"> </span>

var $total = $('#usertotal');
$('input,select').change(function () {
    var tot = 0;
    $('input:checkbox:checked, select > option:selected').each(function () {
        var per_op = $(this).attr('value');
        if (per_op) {
            tot += Number(per_op);
        }
    });
    var final_result = tot.toFixed(2);
    $total.html(final_result)
});