Electrical bills for running a computer? It's the monitor that eats the power, not the processing. What is it to be used for (echoing earlier question)?
My suggestion, supplier close to me so shop around for similar closer to home: PC with no operating system. Less than £200. Add a monitor and all the bits, OK, around £300 total, assuming youare VAT registered. Take a look at
CCL Online's offering, the second one down in the list with the AMD CPU. Intel have some extremely serious security questions to address before I'll see them as viable again.
Put Ubuntu on it. Support is everywhere. Get in touch if you can't find any locally and we'll point you at it. Comes with full internet capabillities including browsing and email, full office suite, graphics manipulation and design software and much more, all free.
Now, tell your staff to press the power switch on the monitor, the switch they can see and reach so it's easy, at the beginning and end of each session. No having to boot up and down again, just turns the power-hungry screen on and off.