If you already have the data from the Energy going into a field named
electricity then you re 90% there. As Tom said, if your WeeWX field (ie
electricity) contains the number of kWh consumed in an archive period (I
assume this is five minutes) then using the tag $month.electricity.sum in a
WeeWX report template will display the month-to-date electricity usage. If
the electricity field holds a cumulative kWh value (ie the electricity used
in a five minute archive period is the difference between successive
values) then the $month.electricity.diff tag will display the month-to-date
electricity usage. These tags will actually return a formatted string, if
you want to do some maths on the month-to-date usage value then owe need
to do things a little differently. There are a couple of different ways you
could do this but the easiest approach for some simple maths is to include
some in-line python code in a WeeWX report template. Let's say the cost of
electricity is 20 cents per kWh, the electricity field contains the archive
period electricity usage and you want to display something like:
Usage this month: 283 kWh
Cost this month: $ 56.60
In this case you would add the following lines of code to your template
(untested):
#set $mtd_cost = round($month.electricity.sum.raw * 0.20, 2)
Usage this month: $month.electricity.sum
Cost this month: $ $mtd_cost
The first line of code obtains the month-to-date electricity usage (ie the
sum) as a number (.raw gives us a number instead of a string) which we
multiply by 0.2 (the cost of 1kWh) and then round the result to two decimal
places. This value is assigned to the variable mtd_cost. The second line
displays the month-to-date usage in kWh, I expect that rather than
displaying 283 kWh it probably displays something like 283.134356. No
problems, we just need to let WeeWX know that the field electricity
contains values in kWh - we will come back to that later. The third line
displays the month-to-date cost in dollars using the value we calculated in
the first line. WeeWX has no knowledge of currency so we have to manually
format the cost ourselves through use of the round() function in the first
line and the dollar sign literal (the first dollar sign) in the third line
(note the space between the dollar signs on the third line, this is
important).
This code has a couple of limitations. As I mentioned, unless we let WeeWX
know that the electricity field contains values in kWh the automatic
formatting of $month.electricty.sum won't work properly. Secondly, if your
Efergy ever has a hiccup, or for some reason there is no data in field
electricity for the month, the tag $month.electricity.sum.raw will return
the python value None and the calculation in the first line of code will
return an error and the template will abort.
To tell WeeWX that field electricity contains values in kWh add the
following code to the bottom of /home/weewx/bin/user/extensions.py or
/usr/share/weewx/user/extensions.py (depending on how you installed WeeWX):
# override the default units for group_energy and set to kWh
weewx.units.USUnits['group_energy'] = 'kilo_watt_hour'
weewx.units.MetricUnits['group_energy'] = 'kilo_watt_hour'
weewx.units.MetricWXUnits['group_energy'] = 'kilo_watt_hour'
# set default format and label for kilowatt hours
weewx.units.default_unit_format_dict['kilo_watt_hour'] = '%.1f'
weewx.units.default_unit_label_dict['kilo_watt_hour'] = ' kWh'
# define conversion functions for energy
weewx.units.conversionDict['watt_hour'] = {'kilo_watt_hour': lambda x: x /
1000.0}
weewx.units.conversionDict['kilo_watt_hour'] = {'watt_hour': lambda x: x *
1000.0}
# assign database field electricity to group_energy
weewx.units.obs_group_dict['electricity'] = 'group_energy'
The above code:
(1) tells WeeWX to override the units used for energy from the default Wh
to kWh
(2) sets the default formatting and unit label for fields in kWh to one
decimal place and 'kWh' respectively
(3) defines conversion functions allowing conversion between Wh and kWH and
vice versa (not strictly required in your case but handy to have since we
are in here)
(4) tells WeeWX that the field electricity belongs to group_energy (which
we have already set to use kWh by default). Refer to the section Assigning
a unit group <http://weewx.com/docs/customizing.htm#Assigning_a_unit_group>
in the Customisation Guide for a little more background.
To handle the condition where $month.electricity.sum.raw is None we need to
change our in-line python code. Change the first line:
#set $mtd_cost = round($month.electricity.sum.raw * 0.20, 2)
to something like:
#if $month.electricity.sum.raw is not None
#set $mtd_cost = round($month.electricity.sum.raw * 0.20, 2)
#else
#set $mtd_cost = '---'
#end if
Now if $month.electricity.sum.raw returns the value None we simply display
--- as the month-to-date cost otherwise we calculate it as before.
That is probably a lot to take in, especially if you are not familiar with
python and WeeWX. See how you go and post back here if you have any issues
or further questions.
Gary
On Wednesday, 7 September 2022 at 13:01:53 UTC+10 [email protected] wrote:
> yes it is kilowatt-hours (kw) the kit is made by efergy.
> we have added electricity column to the database and the sensor data in
> (kw) is logged to database every 5 minutes and it is in agreement to what
> the kit display is showing in (kw).
> the display shows the consumption (kw) per day , week, month ,year but we
> can not adjust the tariff for our need and we believe it is hardcoded in
> the firmware.
> in order to get the cost per month we need to have the kw consumed during
> the month but we do not know how to do it within weewx.
>
> On Wednesday, September 7, 2022 at 4:29:45 AM UTC+3 [email protected]
> wrote:
>
>> The unit "Kilowatt per hour" doesn't make a lot of sense (perhaps you
>> mean kilowatt-hours?), but putting that aside, usually you record (in the
>> database) either the amount of energy used during the archive period
>> (typically 5 minutes), or you record an "accumulated energy" since the last
>> reset of the monitor.
>>
>> If the former, you end up with tags such as $month.*delta_energy*.sum,
>> if the latter, $month.*accumulated_energy*.diff.
>>
>> Either way, the units are energy, typically watt-seconds, watt-hours, or
>> kilowatt-hours.
>>
>> We'd need more information to get more specific. In particular, you
>> didn't say who built the monitor.
>>
>> -tk
>>
>>
>>
>>
>> On Tue, Sep 6, 2022 at 6:07 PM Mks Mk <[email protected]> wrote:
>>
>>> we want to expand the use of weewx to include energy consumption and
>>> cost calculation but we are not sure how to do that.
>>> our setup consists of:
>>> 1-weewx on raspberry pi 4
>>> 2-SDR dongle
>>> 3-energy monitor device kit with RF transmitter and display
>>>
>>> we are capturing the signal of acurite weather station and the energy
>>> transmitter and weewx reading is matching what the energy display reading
>>> in kilowatt per hour and the reading gets updated every 20 seconds.
>>>
>>> we need weewx to calculate the consumption of energy during 24 hours and
>>> the total consumption for the month (30 days) but we are sure if weewx can
>>> do this task and we are not sure how to do this.
>>> any thoughts or suggestions to accomplish the task
>>>
>>> thank you
>>>
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