# Virtual heat meter / Software heat meter

**URL:** <https://community.openenergymonitor.org/t/virtual-heat-meter-software-heat-meter/26535>\
**Category:** Heatpump\
**Created:** [10 August 2024 05:56 UTC](https://community.openenergymonitor.org/t/virtual-heat-meter-software-heat-meter/26535 "2024-08-10T05:56:10Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Alex9](https://community.openenergymonitor.org/user_avatar/community.openenergymonitor.org/alex9/32/29516_2.png) [@Alex9](https://community.openenergymonitor.org/u/Alex9)\
**Post date:** [10 August 2024 05:56 UTC](https://community.openenergymonitor.org/t/virtual-heat-meter-software-heat-meter/26535/1 "2024-08-10T05:56:11Z")

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I’m looking for a algorithm to calculate thermal output KW/h.

My heat pump have a DC water pump.

Over Modbus/ mqtt is possible read follow l/min and flow and return temperature.

The issue is first minute data and when is defrosting.

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**Author:** ![glyn.hudson](https://community.openenergymonitor.org/user_avatar/community.openenergymonitor.org/glyn.hudson/32/35003_2.png) [@glyn.hudson](https://community.openenergymonitor.org/u/glyn.hudson)\
**Post date:** [11 August 2024 00:22 UTC](https://community.openenergymonitor.org/t/virtual-heat-meter-software-heat-meter/26535/2 "2024-08-11T00:22:47Z")

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You’ll need to do a mass flow rate calculation, see: [https://docs.openenergymonitor.org/heatpumps/basics.html#mass-flow-rate-heat-transfer](https://docs.openenergymonitor.org/heatpumps/basics.html#mass-flow-rate-heat-transfer), you can do this in Emoncms input processing.

You want to include minus data for defrost in the calculation since this is heat being subtracted from the house, but it’s a very small amount.