I leave my main machine active all the time, as it also works as the server for other computers. Only the monitor is allowed to sleep. I recently upgraded most of its internals, with a modern motherboard, i7-8700K, 32GB memory, 512GB NVMe SSD, AMD RX 580 Nitro 8G graphics card. It has a Corsair 850W power supply, and a 4TB WD drive. I thought it would be interesting to get an idea how much power it uses. This would also give a very rough idea of the adequacy of the power supply (inaccurate because ideally one would know the power on each of the output voltage lines, and power supplies are far from 100% efficient.) So I bought a cheap power meter from China. You plug an appliance into it, plug it into a power socket, and a digital display tells you how many Watts are being used. Here are the results. The monitor is not included, it has its own power lead. Idle: 70W Prime95 (drives CPU and memory hard, 100% CPU): 200W FurMark (drives GPU hard): 300W dropping to 260W Prime95+FurMark: 440W dropping to 380W I think the reason the power drops is that the GPU hits 85 degrees and the AMD software then reduces the GPU performance to avoid overheating. I am pleased to see that when idle it uses so little power. The maximum of 440W shows that I should be well within the limits of the power supply, even as it ages.