How to create a template to start a timer (helper) if new state (number) is smaller than the previous state

Configuration
1

Hi,
I want to know how much time is remaining of the 15 minutes power peek monitoring of my electricity meter.
the dsmr_parser does not creates any time_stamps for HA, and the time of the electricity meter is slightly off than my HA time.
i am struggling to start the created countdown timer helper for 15 minutes if the new state is smaller then the previous state.
i can not use below or greater than in a automation, it will not alleyways start at 0 after 15 minutes.
I know this is not 100% ( if my solar production is less than my house consumption in these 15 minutes it will trigger this also, after that i will be correct.
So example state = 0.254 kW new state = 0.004 kW → start 15 min timer because new 15 min peek value has started !

2 

alias: decreasing trigger value
description: ""
trigger:
  - platform: state
    entity_id: sensor.example
    not_to:
      - unknown
      - unavailable
    not_from:
      - unknown
      - unavailable
condition:
  - condition: template
    value_template: "{{ trigger.to_state.state|float < trigger.from_state.state|float }}"
action:
3

Great,
works as expected ! thanks !