For a typical interior system of 2kW, the electricity usage is approximately 600W, causing an a/c cost of around 20p per hour per indoor device at 28p/kWh. http://Cover.searchlink.org/test.php?a%5b%5d=%3ca+href%3dhttp%3a%2f%2fwww.webwiki.at%2Fpalmersgreenhvac.co.uk%2Fair-conditioning-repair.html