If you have a photovoltaic (PV) system connected to APS and do not have other monitoring of the PV system such as that provided by most inverter manufacturers, it is not easy to determine the solar production that corresponds with the monthly electric bill. APS requires a solar production meter and this data is recorded and made available to the customer, but with a little difficulty. The following example is based on the now grandfathered 'Net Metering' (rate rider EPR-6) wherein any excess PV production, measured in kilowatt-hours (kWh) is used to offset energy delivered by APS. This method has been replaced by a system APS calls RCP, utility speak called 'Resource Comparison Proxy' (note that the APS website was developed by utility personnel using their view of the situation, not the customer view). The Solar Center intends to repeat the following procedure later with examples based on RCP.
Look at the recent example of an APS electric bill and see if you can determine the solar production:
The APS bills show only that 186 kWh in this case was net metered. The bill does not show the solar production that was directly used, to determine this one has to have an APS web account (free) and has to go online to learn more. There is a lot of data available. Note the 'Meter reading' dates above, this will be used later to calculate the solar production. Using a browser such as you are using to view this article, go to https://www.aps.com/
There is presently a Capcha screen to prove that a person and not an automated computer is accessing the website. Enter the requested data.
Enter your APS username/password then click login. If you do not already have a username and password, click on 'register'. The following is typical.
Next select 'daily and hourly usage'. Solar production is a subset of usage for some APS reason.
There are four types of data available and a calendar to select the dates to view. See the red instructions in the examples below. In APS jargon 'received usage' is solar production. This screen shows the solar production graphically, good for seeing relative production that depends on the sunshine and to a lesser extent the air temperature. Clicking on the 'Day' tab will expand that day, otherwise a month (or the current month to date) is displayed.
This view shows the pattern of the energy drawn from APS. Actual total usage at a specific time will be higher since PV system production will be used directly if there is enough usage at the specific instant.
Note that on each of the above examples, there is a down arrow next to the 'for service at' section and that clicking on this down arrow shows a second service, the PV production Meter with an '*'. The address is blurred in this example. Select the line with the *.
The production data is displayed in two formats, a bar graph for the month, and a graphical format for the week.
In order to get values for calculations, the monthly summary data needs to be downloaded as Excel files, usually for the two months that include the date range of the electric bill. With the 'daily energy useage' tab selected, select the first month of the range (click on any date), then click on the 'download meter data' text link over the calendar. This will download a file named 'Excel.xlsx' ( or Excel(y).xlsx where 'y' is a digit, added by your computer when 'Excel.xlsx' already exists). A spreadsheet program is needed to open and view these files, Excel for example. Select the 'daily energy usage' and 'delivered useage' tabs. The Excel data will look like this:
The values for the billing date range, July 25 to August 23 in this example, need to be added. This can be done with the spreadsheet program or manually. In this example the sum is 711.5 kWh. This is not straight forward since the values shown are actually text and Excel can not directly add them. Use the =value(cell) function in another column to convert the text to actual values. Now that the actual solar production is known, the below chart shows the relationship of these values.
The calculation of Home useage is (Solar Production) + (Purchased from APS) - (Sold or net metered to APS).