# Power Calculations

**URL:** <https://community.homey.app/t/power-calculations/25430>\
**Category:** Questions & Help\
**Created:** [February 3, 2020, 3:14pm UTC](https://community.homey.app/t/power-calculations/25430 "2020-02-03T15:14:54Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![Par\_Norberg](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/par_norberg/32/17840_2.png) [@Par\_Norberg](https://community.homey.app/u/Par_Norberg)\
**Post date:** [February 3, 2020, 3:14pm UTC](https://community.homey.app/t/power-calculations/25430/1 "2020-02-03T15:14:54Z")

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Hi, I have a Power Meter (NorthQ Power Meter) that calculates my whole house energy consumption by counting the led pulses in my analog power meter.

However the return is just the number of pulses (Watts) so in order to get the consumption I need to calculate the pulses between a certain interval (say 1 minute). And then multiply by 60 to get the watt hour:

_Time Watt Wh_  
10:00 123456789  
10:01 123456799 (123456799-123456789)x60

The value of the Wh i want to store someware to show in a graph later on. So questions:

How do I set a variable every minute?  
I guess I need to set two variables to be able to subtract them?  
How do I store the third variable (Wh) so I keep the history?  
And how do I mark it so Homey recognise it as power consumption.

Thanks!  
Pär

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**Author:** ![Igy](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/igy/32/22144_2.png) [@Igy](https://community.homey.app/u/Igy)\
**Post date:** [February 3, 2020, 3:24pm UTC](https://community.homey.app/t/power-calculations/25430/2 "2020-02-03T15:24:48Z")

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Create VD and assign calculated value to it every minute. In my case I do calculate and assign negative power from one clamp to VD so the overall consumption is correct.  
[https://homey.app/f/ILCFb0](https://homey.app/f/ILCFb0)

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**Author:** ![David\_K](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/david_k/32/10319_2.png) [@David\_K](https://community.homey.app/u/David_K)\
**Post date:** [February 3, 2020, 4:13pm UTC](https://community.homey.app/t/power-calculations/25430/3 "2020-02-03T16:13:34Z")

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There was an app that had some math functions. Check better logic app. Idi not use it but maybe it can help you.

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**Author:** ![JPe4619](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/jpe4619/32/9017_2.png) [@JPe4619](https://community.homey.app/u/JPe4619)\
**Post date:** [February 3, 2020, 4:18pm UTC](https://community.homey.app/t/power-calculations/25430/4 "2020-02-03T16:18:10Z")

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> [@David\_K](#):
>
> math functions

With Logic you can do Math. no app needed.  
 ![image](https://us1.discourse-cdn.com/flex025/uploads/athom/original/3X/e/5/e58a6e33fd599cfa1741d2fda2fc35291eab6246.png)

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**Author:** ![Christer\_Dahlberg](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/christer_dahlberg/32/17209_2.png) [@Christer\_Dahlberg](https://community.homey.app/u/Christer_Dahlberg)\
**Post date:** [February 4, 2020, 8:56am UTC](https://community.homey.app/t/power-calculations/25430/5 "2020-02-04T08:56:35Z")

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Hi. Which app did you use to add NorthQ’s Power Meter into your Homey?

Regards Christer

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**Author:** ![Par\_Norberg](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/par_norberg/32/17840_2.png) [@Par\_Norberg](https://community.homey.app/u/Par_Norberg)\
**Post date:** [February 4, 2020, 9:18am UTC](https://community.homey.app/t/power-calculations/25430/6 "2020-02-04T09:18:47Z")

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Hi, I use abeggled/com.northq on GitHub.

br  
Pär