Each meter has a “Start” and “End” date. You simply need to make sure the Start and End dates are updated for each meter, and Portfolio Manager will take care of the rest. Your property must always be covered by at least one meter (you can’t have a break with no active meters, even for 1 day).
For example, say you install a new central meter on Jan 15, 2016, and take your 3 current meters offline on Jan 30, 2016. You would add the new meter, starting Jan 15, 2016. And update the 3 older meters to show they became inactive on Jan 30, 2016.