Measuring P and Q of house appliances
Measuring AC power requires specialized equipment, unless the load is purely resistive.  Not only do you have to measure the voltage and current, but you must also measure the phase difference between the two.  Standard multimeters cannot do this.

Here is a short introduction to AC power measurement.

I would recommend using the "Kill-A-Watt"-style product:



It is easy and inexpensive (less than $20 USD).  It can tell you how much real power is being used, the instantaneous voltage and current, what the power factor is, and so on.  It will even keep a running total for you so you can see average power usage over a long period of time.

Here's the Kill-A-Watt on Amazon.com.  It is only good for 120VAC mains.

If you have 230VAC mains, the Prodigit 2000MU-UK (pdf) looks like a decent option.