I tried a calculator and it says I probably use between
231W(It wouldn't let me choose mixed ram so I chose 2x8G),
231W(it let me choose 2 types of ram), and
276W(it didn't let me select 4G & 8G RAM so I chose 16G x1).
On my system I have just the barebones meaning the stuff it came with so it has only the CPU(65w apprently), DVDRW, RAM, and 1TB(5400rpm?) hard drive it came with. Two of them asked how long I use the computer about 8 hrs a day. Some days I don't use it at all and other times I'm only most of the day.(like most people it varies)
The only things I have connected to it are my printer(Pixima) which is off 99% of the time(It's on USB but can go wifi or bluetooth), a tablet drawing pad(I'll probably disconnect as I never use it and it's USB), my keyboard & mouse(basic but USB), and my microsoft headset(USB but not generally in use). I have two powered 45w speakers that plug into the audio jack, a Acer E series 1920x1080p monitor(connected through video card on HDMI/DVI converter cord). I just installed a 1650 video card.(rated for a 300w psu and it's energy consumption is 75w)
I don't know if I need to upgrade. If I do I probably only need a 350w to 450w psu. 450w and 500w are quite affordably priced at between $45 to $70. They seem to come with a 120mm fan. I do have a old 750w thermaltake but it is a bit much for what I need and is over 3 years old. I've been looking at the Coolmax, Enermax, Thermaltake, and EVA. I have more experience using the Thermaltake(750w), an Enermax(can't remember but think it was a 350w). The supply they come with is ok. It's a common supply used with intel products. However years ago my 386 or 486 needed it swapped. My 750w was on a Athlon II X3(2G ram I think).
I'll probably upgrade due to psu warranty, etc but I don't put a heavy load on it. I just basically play wow and surf the net. However I'm about to get a thermal sensor 80mm fan. If it doesn't bring down the temp I might switch the gtx1650(75w) to a GT1030 2G(20w and it seems to have a fan but no listing on how warm it gets).