# Understanding Unit Hour Utilization

Unit Hour Utilization (UHU) is one of the most widely used and misunderstood measurement metric used in the vast majority of EMS Agencies today. The metric has gained notoriety thanks to Jack Stout’s System Status Management solution for ambulance deployment. It has become the universal EMS measuring metric for agencies to gauge performance regardless of agency type or primary goal.

## How To Calculate UHU

There are actually a couple of different ways to calculate UHU but the simplest way (what we will call Simple UHU) is calculated by dividing the number of hours a unit works into the number of assignments it handles. For example, a unit that works 10 hours and handles 5 assignments would have a simplified UHU of a .5. Generally the higher the number is the more effective and efficient the system is considered to be.

There are a few other ways to calculate UHU that you may need to understand.

Payroll UHU – For the budgetary minded system there is the Payroll UHU. To determine this UHU you take the total number of hours worked by your field providers, divide that by 2, then take that number of hours and divide it into the number of reimbursable assignments handled. This type of UHU is generally used for specific garage locations

For example: You have a total of 20 Medics who worked 10 hours for a total of 200 hours and have completed 50 reimbursable assignments. We divide 200 by 2 for 100 Unit Hours (it takes two to make an ambulance crew) and then divide that into 50 to get a Payroll UHU of .5. If we took the same numbers and did a Simple UHU, we would have 10 units working 10 hours (100 hours) and completing 50 assignments for a Simple UHU of .5 as well.

Suppose that out of those 50 assignments there were only 45 reimbursable assignments (for argument’s sake there were 5 Refusals) then we would be dividing 100 into 45 for a .45 Payroll UHU.

Now let’s say that 1 of those 20 Medics didn’t come to shift due to an upset stomach. Instead of sending him home you used his partner for the 10 hours in Logistics fixing regulators and stocking trucks. If we calculated the Payroll UHU, we would divide 190 (because one person of 10 hours is out) by 2 for 95 Unit Hours divided into the 50 assignments to get a Payroll UHU of .53 (it’s 0.52631579 rounded up to the nearest one hundredth). If only 45 of the assignments were reimbursable then the Payroll UHU becomes .47 (it’s .47368421 rounded down). If we calculated a Simple UHU, we would have 9 units working 10 hours (90 hours) and completing 50 assignments for a Simple UHU of .55.

Notice the difference? When you start adding the variables of a unit not being out there but still paying for half a crew and having assignments that are not reimbursable, the UHU starts to get worse and worse.

In Service UHU – For the performance minded system there is the In Service UHU. Unlike the other UHUs, some systems do not consider a higher number as being better. To determine this UHU you take the total number of hours your units are in service and divide it into the number of assignments handled. This type of UHU is generally used for system-wide assessments.

For example: You have a total of 10 units scheduled to work 10 hours each and they handle 50 assignments. This would give you 100 unit hours divided into 50 for a Simple UHU of .5. It takes each unit 15 minutes to check out their ambulance and come in service with the dispatcher, so that is 2.5 hours (150 minutes) of time where they are technically out of service. That means that your In Service UHU is actually 97.5 unit hours divided into 50 for an In Service UHU of .51. If one of your units breaks down for 2.5 hours, your In Service UHU becomes .53 because now you only have 95 hours of in service time.

## Which UHU Is Right For You?

The type of agency and the goals of the service will direct you towards which UHU is best to use in order to measure your agency. Many managers misunderstand UHU as the be all end all of efficiency and that simply is not true. UHU provides the metric to measure and compare efficiency when planning to meet the needs of your system and is only one tool that the successful EMS Manager and EMS Leader needs in their toolbox.