PC power(W) consumption calculation using multimeter?

Question

I have cut spare PC power cord and hooked up my multimeter to measure AC Amperes. It ranges depending on load from 0.9A to 1.5A (that's + LCD monitor). Voltage coming out of the mains is 240v. According to my "Success in electronics" book (and other materials online) to calculate power(W) you have to multiply current(A) and voltage(V). Result I'm getting is that my PC consumes 264watt every second at drain of 1.10A. To calculate drain every hour I multiplied this by 3600, result 950400watt/hour. It seems too much, what am I doing wrong?

Answer 1

You're getting power and energy confused there. You don't need to multiply by 3600. If something is drawing 264 watts, it will use 264 watt hours, or 0.264 units (KWh) of electricity, per hour. The watt is the equivalent of joules per second - your calculation gives you joules per hour.