Jedinite24 is correct. Try using a Kill-A-Watt meter. It's very simple to use. I use one at my house. Otherwise, you're just guessing. You enter in the cost of your electric rate and then plug in your devices. It then calculates the daily, monthly, and yearly cost. Leave it on with the equipment running on idle for about an hour and that's all you need. The Kill-A-Watt is designed to go between equipment and then accurately calculate draw. However, since you only want to figure idle time, that's all you need to do is plug it in and leave it. In reality, you will have results in as little as 5-10 minutes.
In your case, plug everything into a power strip and then put the power strip into the Kill-A-Watt and you'll have an accurate idea of the total draw of the entire system.
In your case, plug everything into a power strip and then put the power strip into the Kill-A-Watt and you'll have an accurate idea of the total draw of the entire system.