Approximately how much electricity per hour does a Macbook Pro 7.1 plugged into the wall use with a dead battery? It's a 60W MagSafe Power Adaptor. I mostly surf the internet and read on the kindle ap and play mp3's.

reebeerocks17,

the worst case with a 60 W adapter — if it were continuously consuming the maximum possible electricity all day, every day, for three months straight — would be 60 W × 24 hours/day × 91 days (three months) = 131,040 W·h = 131.04 kW·h. Multiply that by the cost of electricity per kW·h to arrive at the absolute maximum cost; for example, if your boyfriend’s mom’s electricity costs 15.3¢ per kW·h, then the absolute maximum cost would be

131.04 kW·h × 15.3¢/kW·h = 131.04 × $0.153 = $20.05.

Again, this is presuming a particular cost per kilowatt·hour, and that it was using the maximum possible electricity for 24 hours/day, 7 days/week, 13 weeks/three months. Adjust the total according to the actual cost of her electricity and to the actual usage of your MacBook Pro during those three months.

I cannot find info for your model but there is this for a retina 15 inch MacBook Pro.

Energy consumption is shown for various configurations.

http://images.apple.com/environment/reports/docs/15inch_macbookpro_retina_per_fe b2013.pdf

Items to consider, how long the system is powered by the AC Adapter, do you leave the computer in standby or charging when not in use.

The best way is to use a power monitor, this is a UK model but there must be one for your country.

http://www.amazon.co.uk/Plug-In-Power-and-Energy-Monitor/dp/B000Q7PJGW

At $150 you could have bought a new battery, she may well be right, I don't know how expensive your power is.

reebeerocks17,

no, I’m just someone who knows multiplication; I’m sure that you do, too. I hope that your boyfriend’s mom will be able to find a more effective way to reduce her electricity bill.