Well I used to turn off the monitors and leave it running...And the last month I started actively suspending it, and the bill went down. I'm waiting to setup some sockets with smart power measuring features, and I'll have more reliable data on power consumption...but I'm afraid I might need to wait a few days on these.

Good call. Though, if you use natural gas for heating and water heating and don't own any AC... It'll be a lot less energy in total and you'll notice a new gaming PC. Especially if it coincides with a new game you've been playing nonstop for a few weeks. But I agree, there are a lot of electrical devices in a regular home. And my usage changes with the seasons. For example I watch a lot more TV when it's rainy and cold outside, and the TV is like 100W. And I turn on the lights hours before I'd need them in summer. And it's difficult to tell apart the things in a home just by looking at an electricity bill.

You should have a look at your computer, though. Have you had a look at powertop? And I suppose there is a tool for AMD graphics cards to tell you if it's running at full speed all the time or clocking down as it's supposed to. Or you could get a power meter to plug your PC in to. And do a measurement with GPU and one with the thing ripped out entirely.