That is quite a lot. The table in [1] shows that an average 9V battery has a capacity of about 3.5Wh, meaning you can use this calculator for a little over half an hour on a single battery.<p>[1] <a href="http:&#x2F;&#x2F;www.zbattery.com&#x2F;zbattery&#x2F;batteryinfo.html" rel="nofollow">http:&#x2F;&#x2F;www.zbattery.com&#x2F;zbattery&#x2F;batteryinfo.html</a>