Dear Thi4
This is a peculiar problem associated with remote area where you have to depend on DG sets as the grid supply is not available. 2 DG sets are OK but as others pointed out you have to run one and the same DG set whether you require only bulbs-on or motors to operate. My suggestion is, at best you should have smaller DG set say 25 kva or 100 kva and also 100, 580 kva etc as you might require depending load to be connected. For e.g. during off duty you might run only for lighting for which a 25 kva smaller DG set should suffice. Likewise when on duty during which you have to run other equipment, machines etc so the load will increase and hence you have run bigger DG set say 580 kva and so on. To enable this you can have dedicated line for lesser consuming items like lighting, fans etc which can be connected with a smaller set and others via a separate line with a bigger set on. In other words, as you know, you don't use a crane to lift a Desk Top PC but at the same time you deploy bigger crane to lift and move a CNC m/c. Thus it will help you to lessen or optimise diesel consumption. Both can also be connected thru' a common meter to ascertain units consumed vis-a-vis hours of DG run and diesel consumption. One more method is you have to maintain register/folio of every light, appliances & equipment and note down no.of minutes they are on and you can compute the units consumed by every such units by applying rated capacity of those items. Since bulbs, fans and other office eqpt. like PCs/printers etc. consumes comparatively less power it's not likely to answer your high cost of power. Whereas you have to watch dry run of your connected eqpt. and m/cs to have effective control.