One of the most common and misunderstood issues surrounding schedules is the relationship between staffing, overtime and the schedule itself.
The reality is that a schedule has no impact on the quantity of overtime your site is experiencing.
Overtime is a function of (1) How much work is there to do and (2) How many people do you have to do that work.
Your schedule only tells you “when” the overtime will occur.
If you take a look at all the hours it takes to get a job done, and then look at how many people you have to do the work, you will know how many hours per person will be needed.
If you have 4,200 hours of work to be done next week and 100 employees to do it, then everyone will average 42 hours of work for an overtime rate of 5%. Notice that the schedule played no role in determining this figure.
So where does a schedule come into play?
In most cases, a schedule will tell you “when” the overtime will occur.
For example, if your schedule has short shifts (i.e. 8 hours or less), the overtime is typically worked before or after a regular shift. There are two reasons for this. First, the shift is short enough that you can add hours to it without adversely impacting safety or productivity. Secondly, the shorter the shift, the more days of work your schedule will have. This means you have fewer days off. The fewer days you have off, the more you want to protect them. Therefore, if you have to work overtime, you’d rather do it on a day when you are already at work rather than giving up one of your preciously few days off.
If you have longer shifts (i.e. 10-hour or 12-hour shifts) then overtime is much more likely to occur on a regularly scheduled day off. There are two reasons for this. First, the longer the shift, the fewer hours you can add before the shift become too long and begin to adversely impact alertness, safety and productivity. Secondly, longer shifts have many more days off. More days off has the impact of lessening the value of a day off, (In much the same way that diamonds would be less valuable if they were laying around everywhere.) This means that it is less painful to give up a day off, when you have a lot of them.
There is one condition where the schedule can play a role in the “quantity” of overtime – When you have the wrong schedule to begin with.
The wrong schedule can cause you to take the “perfect” number of people and put them in less than perfect locations. For example, if you have the right number of people but your schedule causes you to be overstaffed during some time periods; you will then be under staffed during other time periods. This will cause overtime. More importantly, they will cause Idle Time when you are overstaffed along with the Overtime for when you are understaffed. Both of these conditions create high avoidable costs that can be eliminated with the right schedule.