Here’s where I ended up… I hope this helps others.
I have a sensor that detects the rate of water flow (out of a pump for my pool) in gallons per minute. Here’s what its past 24 hours looked like changing rates throughout the day:

I then needed to create an “integration sensor” to sum up the integral (the area under the GPM line) which will give me the quantity of gallons pumped:
- platform: integration
name: pool_cycle_flow_integral
source: sensor.pool_pump_flow_rate
unit_time: min
unit: "Gallons"
round: 0

That number seemingly never resets (maybe on restarts?), so i needed a sensor that summed up the difference from midnight to now. Possibly could have done this with a combination of Statistics sensors and template sensors … but the Utility Meter did exactly what i needed:
pool_cycle_gallons_today:
source: sensor.pool_cycle_flow_integral
cycle: daily
The last thing I added was a “turn overs today” sensor which is just a simple template sensor with some algebra, but it’s based on top of all of these other sensors… so i thought i’d include it here:
- platform: template
sensors:
pool_cycle_turnovers:
value_template: "{{ ((states.sensor.pool_cycle_gallons_today.state)|int / 13000)|int }}"

