I've written several articles about 12-hour shift schedules in 24/7 operations. Here are links to the most popular ones:

1. https://www.shift-schedule-design.com/12-Hour_Shifts
    
2. https://www.shift-schedule-design.com/Blog?m8:post=12-hour-shifts-in-smaller-companies
    
3. https://www.shift-schedule-design.com/Blog?m8:post=matching-12-hour-shifts-to-your-workload-distribution
    
4. https://www.shift-schedule-design.com/Blog?m8:post=covering-absences-on-a-12-hour-shift-schedule
   
   
5. https://www.shift-schedule-design.com/Blog?m8:post=are-12-hour-shifts-too-long
    

I also sell 2 packages with 10 different options: one with only 12-hour fixed shifts and another with only 12-hour rotating shifts. You can read more about this here:  Schedule Examples

Most 12-hour shift schedules for 24/7 coverage use 4 crews. When you divide the hours in a week (168) by 4 crews, you get a average of 42 hours/week. With 12-hour shifts, this will require half the work weeks to be 36 hours (three 12-hour shifts) and half to be 48 hours (four 12-hour shifts). 

In many organizations, especially public agencies, avoiding overtime is a high priority. They view overtime as evil or an unnecessary expense. I have repeatedly tried to argue the fallacy of this belief, yet I continue to get requests for 12-hour schedules with no overtime in them. Here are 2 articles on this topic:

1. http://www.shift-schedule-design.com/Overtime_Issues
2. https://www.shift-schedule-design.com/Blog?m8:post=why-eliminating-overtime-in-24-7-schedules-can-be-costly, 
   

Reducing the hours of work to 40 or less a week will result in gaps in the coverage and will require additional personnel to fill the gaps. In most cases, this is more expensive than simply keeping overtime in the schedule. In addition to higher costs, this will also require other sacrifices as seen in the following four approaches to eliminating overtime in 12-hour schedules for 24/7 coverage. 

Here is a key to the symbols used in the schedules below:

D12 = 12-hour day shift

N12 = 12-hour night shift

d8 = 8-hour day shift

n8 = 8-hour night shift

d4 = 4-hour day shift

a4 = 4-hour afternoon shift

e4 = 4-hour evening shift

n4 = 4-hour night shift

Here is how the schedules work. When the schedule first starts, the crews are assigned to specific weeks in the cycle. Crew A is assigned to start in Week 1, Crew B is assigned to start in Week 2, and so on. At the end of each week, the crews rotate down to the next week in the cycle. Crew A moves to Week 2, Crew B moves to Week 3, etc. When a crew completes the last week, they rotate up to Week 1. 

1. Eliminate the 48-hour work weeks. This sounds simple enough. Just change all the 48-hour work weeks to 36 hours by eliminating one of the shifts. To maintain the same coverage, this will require 5 crews (a 25% increase in headcount), rotating shifts, and a 4-hour pay cut for all employees. (Note that with fixed shifts, this would require 6 crews). There will also be one shift with double coverage (in the example below, it's the Friday day shift). Here's one example of a 5-crew schedule:

2. Include an 8-hour shift. If you devote one day a week to 8-hour shifts and give one of the three 8-hour shifts to employees who are outside the group (e.g., part-time employees), the remaining four crews would average 40 hours a week. You would have to use a 12-hour work pattern in which the 36-hour weeks and 48-hour weeks are staggered and you would have to be able to average the work hours over a 2-week period (most companies can't do this because of overtime laws). In the sample shown below, the 8-hour afternoon shift on Wednesday would have to be given to employees who are not part of the four crews. That uncovered shift is not shown in the table below.

3. Include a 4-hour shift. If you devote one day a week to 4-hour shifts and give two 4-hour shifts (or one 8-hour shift) to employees who are outside the group, the remaining four crews would average 40 hours a week. This does not require the averaging of pay over a 2-week period or a pattern with staggered 36 and 48-hour weeks. In the sample shown below, there is an 8-hour gap in coverage on Wednesday that would have to be given to part-time employees or someone outside the four crews. That uncovered shift is not shown in the table below.

4. Reduce the work days to 11.5 hours. If you include a 30-minute unpaid meal break in the 12-hour shift, you only have to pay employees for 11.5 hours. You would have to adopt a 12-hour shift pattern in which the 48-hour weeks and 36-hour weeks were staggered. This won't completely eliminate the overtime, and you would have to be able to average the work hours over a 2-week period. An example is shown below:

If you are subject to Federal law that requires overtime after 40 hours a week, you won't be able to use Options #2 or #4. These can only be used by organizations such as police departments that are allowed to average the work hours over a 2-week period.

If you don't have enough part-time employees or you don't have employees from another department to cover the 8-hour gap in coverage every week, you'll won't be able to use Options #2 or #3. You'll either need a 5-crew schedule (see Option #1), a schedule with 11.5-hour shifts (see Option #4), or a crewless schedule that is custom-designed around your staff size.

Let's do a quick cost comparison of 4-crew schedules vs. 5-crew schedules:

• 4 crews * 40 hours/week * 1.4 benefit loading cost  +  4 crews * 4 hours of OT pay/week = 240 hours of pay/week
  
• 5 crews * 36-hours/week * 1.4 benefit loading cost = 252 hours of pay/week

If you already have enough staff to create a 5-crew schedule, here's a way to save money. Keep the OT in the schedule and use your extra capacity to build relief coverage into the schedule to cover absences. Similar to Option #1, you would have a 5-week schedule that averages 42 hours a week. The difference is that the 5th week of the schedule would be devoted to relief coverage.

Doing this would shift the OT from outside the schedule to inside the schedule. When the overtime is outside the schedule, it requires volunteers or forced / mandated overtime. When it's inside the schedule, it is shared equally by the entire staff. In many cases, the total overtime is less. You can read more about this here: https://www.shift-schedule-design.com/Blog?m8:post=you-can-t-eliminate-overtime-but-you-might-be-able-to-reduce-it.

We sell packages of 12-hour shifts for $199 apiece. One packages has 10 options with only fixed shifts and the other has 10 options with only rotating shifts. These all average 42 hours a week. You can read more about it here:  https://www.shift-schedule-design.com/Schedule_Examples.

If you need help designing a 12-hour schedule with no overtime (e.g., to match your pay week or to accommodate a few part-time employees), please fill out this form:  https://www.shift-schedule-design.com/21.html