Understanding your APS Connected Photovoltaic System

Caution- This may be out of date, APS may have changed their website.  APS customers can call APS Customer Service and they can help you with finding your data.

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 effort.  The following example is based on the 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). Under RCP APS purchases all excess PV output at a fixed rate. Some APS customers with older PV systems use 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. For either Net Metering or RCP, the APS bills show only the measurements made by the bi-directional billing meter.  A summary of APS rates is available on our website at: Summary of APS Solar Rate Plans- 2019

Look at the recent example of an APS electric bill and see if you can determine the solar production (not shown):


This APS bill shows that 229 kWh in this case was sold to APS under the RCP rate.  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 matching solar production. Using a browser such as you are using to view this article, go to https://www.aps.com/

The APS website was recently updated.  The top of the page has a Log In.    

APS Web 1

APS Web 3

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.

APS Web 2

Next select the tab 'Billing and Payment', then click on 'View your billing and usage'.  Be patient, this may take a minute or so while the APS website loads your data.

APS Web 4


This is a very useful page. There are really two related pages, 'Energy from APS' and 'Energy to APS'. The above is 'Energy from APS'.  Further detail is available by positioning the cursor over a specific date, this produces a pop-up with details:

APS Web 5 

 In this pop-up: 

Total Produced = PV energy generated

Total Delivered is energy from APS

and the On-peak and Off-peak components

are shown.

Selecting the 'Energy to APS'  tab shows the solar components:

APS Web 6

APS Web 7 

 In this pop-up: 

Total Produced = PV energy generated

Total received is the daily excess energy sold to APS (if RCP) or net Metered to APS.


Each of these pages has a 'Create Report' button. 

APS Web 8

There are 3 options:

Download graph data: This will provide daily values

Billing and usage data:

Peak usage data: 

The 'Download graph data' option downloads a file named downloadGraphView (y).xls wherein the 'y' is used if there are subsequent downloads.  These files have a header and 35 days of data.  If prior data is needed, simply select an earlier month. Typically the data will look like this (two months illustrated):

(Note: Windows 10 identifies these files "The file format and extension of 'downloadGraphView (2).xls' don't match. The file could be corrupted or unsafe. Unless you trust its source, don't open it. Do you want to open it anyway?".  Seems that the actual format is not .xls, but Excel loads the files.

APS Web 9


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.

Cald 11

The calculation of Home useage is (Solar Production) + (Purchased from APS) - (Sold or net metered to APS).


Japan’s largest floating PV plant catches fire

This is not Arizona, but it is a lesson on how high winds can damage a PV system and produce a serious fire. Kyocera’s 13.7 MW floating project at the Yamakura Dam was damaged by 120mph winds the typhoon brought to the coastal city of Chiba. It appears that the wind caused some of the floating array to break loose and pile up such that there was a short circuit in the wiring that produced a fire.

Watch the video at the link below.


Full story at:


 The basic product used in this project seems to be:


Update 2-22-2020

02021 typhoon damage optJapan’s Ministry of Economy, Trade and Industry (METI) has opened a formal investigation into the exact failure mode behind the destruction at the Yamakura Dam floating PV installation. In the end, the ministry seeks to draw up a plan to revamp not just the dam, but also the arrays that are still intact. This is a learning exercise that should be closely followed, as floating PV is enjoying growing popularity.

This is not an isolated incident, only two weeks later, typhoon No. 17 hit the Kyushu region at an average wind speed of 40 m/s, destroying the 2.4 MW Shintaku Tameike floating PV installation, among other damage.

There is a good technocal report at:



Phoenix Solar Requirements- 2019

The City of Phoenix as adopted an Citywide Interpretation concerning New Solar PV Live Loads on Existing Building Roof Structures.

The sub-title is: Adding a new solar Photovoltaic (PV) panel system to an existing building's roof structure where the existing building is not undergoing a change of occupancy.

Basically an interpretation of the 2018 IEBC 303, 502.4, 503.3, 806.2 code. Designers of PV systems ahould review the Interpretation at:


There is also Interpretation covering Solar Panel Connections:


Walmart Says Tesla’s Solar Panels Caught Fire On Multiple Store Roofs

The retail giant is suing Tesla alleging breach of contract after fires on the roofs of at least seven stores.

Walmart has claimed in a lawsuit that Tesla-supplied solar panels on the roofs at several of its stores caught fire because of the tech company’s “widespread, systemic negligence” and its “failure to live up to industry standards.”

The retail giant is suing Tesla alleging breach of contract after fires on the roofs of at least seven Walmart stores with solar panels installed by Tesla’s solar business. These fires, which occurred at stores in several states from 2012 to 2018, cost Walmart hundreds of thousands of dollars, said the lawsuit, filed Tuesday in a New York court.

To state the obvious, properly designed, installed, inspected, and maintained solar systems do not spontaneously combust, and the occurrence of multiple fires involving Tesla’s solar systems is but one unmistakable sign of negligence by Tesla,” the complaint said, according to CNN Business.

Walmart is seeking damages from Tesla and is demanding the company remove all of its solar panels from its stores. The retailer said that Tesla has installed panels on the roofs of more than 200 of its outlets.

Tesla has not responded to HuffPost’s after-hours request for comment.

The lawsuit comes just days after Tesla founder Elon Musk announced the relaunch of its solar rental business. The move, according to TechCrunch, appears to be an attempt by Tesla to revive the “flagging fortunes” of its renewable energy business, which has steadily been losing market share in recent years.

As Reuters noted, the Walmart lawsuit isn’t the only fire-related problem currently affecting Tesla.

The company is also being probed by the National Transportation Safety Board following several deadly accidents involving Tesla Model X and Model S cars that burst into flames.

From CNN

In recent years, Walmart (WMT) installed solar panels from Tesla Energy Operations on the more than 240 stores across the country. The two companies agreed that Walmart would lease or license its roof space to Tesla (TSLA) for the solar panels in exchange for lower energy costs, and Tesla would retain ownership of the panels and handle their maintenance, the filing states. It details fires at seven stores across the country, which Walmart contends all originated in Tesla solar panels and cost the retailer millions in repairs.

 Elon Musk sets bold goals. But has he delivered?

"To state the obvious, properly designed, installed, inspected, and maintained solar systems do not spontaneously combust, and the occurrence of multiple fires involving Tesla's solar systems is but one unmistakable sign of negligence by Tesla," the complaint states.

Walmart alleges that as of November 2018, seven stores had experienced fires as a result of the solar panels, with the first occurring in 2012 in Long Beach, California.

One fire, in March 2018 at a store in Beavercreek, Ohio, caused a large amount of black smoke, forcing employees and customers in the Walmart and in nearby stores to evacuate, the filing states. Walmart said the fire destroyed "significant amounts" of store merchandise, requiring thousands of dollars in replacements as well as building repairs, and the store had to close for eight days.

Walmart says two other, similar fires occurred during that month, after which point it asked Tesla to disconnect the solar panels out of fear "for the safety of its customers, its employees and the general public."

Tesla complied, but another fire occurred even after the panels were disconnected, Walmart claims. The complaint also states that Tesla's own inspections of the solar panel systems installed on Walmart roofs identified some "unsafe or potentially unsafe" conditions."

Walmart said no one was seriously injured in any of the fires.


legal doc

87. Many of the Tesla solar panels inspected by Walmart were suffering from
hotspots, resulting in cracking of the back sheets on solar modules and compromising electrical
insulation. This condition compounded the danger and substantially heightened the risk of fire:
the hotspots reflected an excessive build-up of heat in the solar modules, which in turn wore
down the insulation that was designed to keep electrical currents flowing within their proper
paths and to separate electric conductors from their surrounding materials. These conditions can
readily lead to electrical fires capable of spreading across an entire rooftop.


On Friday, Amazon.com Inc. said a June 2018 blaze on the roof of one of its warehouses in Redlands, California, involved a solar panel system that Tesla's SolarCity division had installed. The Seattle-based retail giant said by email that it has since taken steps to protect its facilities and has no plans to install more Tesla systems. Tesla didn't immediately respond to a request for comment, but said earlier on Friday that it had discovered flaws in a part that the company had used in some of its systems. The part known as a "connector," manufactured by Amphenol Corp., led to "failures and disconnections at a higher rate than our standards allow," Tesla said in an emailed statement. The company has worked to replace it. 11 Amazon sites are generating energy and are monitored and maintained.


also a home problem





Walmart has dropped a lawsuit that accused Tesla of breach of contract and gross negligence after rooftop solar panel systems on seven of the retailer's stores allegedly caught fire. TechCrunch reports:
A settlement has been reached and stipulation of dismissal has been filed with the court, a Walmart spokesperson said in an email. It is unclear what the settlement entails. TechCrunch has requested more information and will update the article if new details emerge. The two companies issued a joint release Tuesday announcing that the issues raised by Walmart have been resolved. "Safety is a top priority for each company and with the concerns being addressed, we both look forward to a safe re-energization of our sustainable energy systems," the emailed statement reads.

Walmart said it sued Tesla after years of gross negligence and failure to live up to industry standards by Tesla, according to court documents. Walmart asked Tesla to remove solar panels from all 240 locations where they have been installed, as well as pay for damages related to fires that the retailer alleges stem from the panels. The lawsuit points to several fires on the retailer's rooftops that allegedly stem from Tesla solar panels.