• Know Your Rights

    Arizona law protects individual homeowners’ private property rights to solar access by dissolving any local covenant, restriction or condition attached to a property deed that restricts the use of solar energy. This law sustained a legal challenge in 2000. A Maricopa County Superior Court judge ruled in favor of homeowners in a lawsuit filed by their homeowners association seeking to Read more
  • Agua Caliente PV Power Plant Among World’s Largest

    The Agua Caliente solar farm near Yuma features First Solar’s thin-film cadmium-telluride (CdTe) solar modules. Located 65 miles east of the city of Yuma, Arizona, this plant is one of the world’s largest operational PV power plants with 290MW (AC) connected to the electricity grid. Read more
  • Solar Hot Water

    There are two types of solar water heating systems: active, which have circulating pumps and controls, and passive, which don't. The typical solar water heater is comprised of solar collectors and a well-insulated storage tank. The solar collector is a network of pipes that gathers the sun's energy, transforms its radiation into heat, and then transfers that heat to either Read more
  • Federal Residential Renewable Energy Tax Credit

    (Information provided by DSIRE - Last reviewed 02/19/2009) Incentive Type: Personal Tax Credit State: Federal Eligible Renewable/Other Technologies: Solar Water Heat, Photovoltaics, Wind, Fuel Cells, Geothermal Heat Pumps, Other Solar Electric Technologies Applicable Sectors: Residential Amount: 30% Maximum Incentive: Solar-electric systems placed in service before 2009: $2,000Solar-electric systems placed in service after 2008: no maximumSolar water heaters placed in service before Read more
  • Solar Building Design in Arizona

    The idea of using the sun to meet the energy needs in our buildings has been with us since the time of the Greeks, with some of the design manifestations even evident in the prehistoric structures of Arizona and the Southwest. There is a great historic tradition for Arizona buildings that utilize our most abundant resource, and the current increases Read more
  • How Not to- Battery Connections

    Photo shows the situation after a battery discharge test at 300 amps was terminated on a 1530 AH IBE battery string when one post melted. During the discharge test all cell voltages are logged. The sum of the cell voltages was 2.73 volts lower than the 48-volt string voltage. This is an average of 118 mv per inter-cell connection, 5-10 Read more
  • 1 Know Your Rights
  • 2 Agua Caliente PV Power Plant Among World’s Largest
  • 3 Solar Hot Water
  • 4 Federal Residential Renewable Energy Tax Credit
  • 5 Solar Building Design in Arizona
  • 6 How Not to- Battery Connections


  1. Solar Center Blog
  2. Guest Blogs
Geoff Sutton
25 November 2017

In the desert south-west the intense sunshine and long summer days result in uncomfortable and even dangerously high temperatures for about four months.

Jim Arwood
28 December 2016

“A lie gets halfway around the world before the truth has a chance to get its pants on.”  --Winston Churchill

Will add Guest Blog content here
Mon, Dec 18, 2017
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Some things to pay attention to in Arizona


The Arizona Solar Energy Association (ASEA), State Chapter of the American Solar Energy Society ASES), will be holding meetings in a follow-up to the-long awaited updated ASES‚  Chapters handbook and directives.

ASES evolution, in response to some problematic economic and operational conditions, has resulted in a hearty and robust context for the present and the future. ASEA is now responding with an appropriate updating, through local and statewide discussion. 

Interim Chair, Andy Gerl, a past ASEA Chair and Board member, is making arrangements for Arizona solar advocates and supporters, members and non-members, to receive both an update re: ASES adaptation and changes, and to discuss solar in Arizona and the “reboot" of the ASEA  context, goals and objectives, within the context of varied renewable energy groups within the State, such as AriSEIA (the solar trade association); various sustainability groups; Green Building organizations; the recently formed solar hot water businesses non-profit entity; research and development at the universities; and others.

For more information about the ASEA Reboot discussions, contact Andy at andrew@blazingsolar.com  or 602-799-5942

APS Rate Case - Higher rates, solar changes now effective as of September 1st

APS customers had until August 31st to submit complete interconnection applications to APS in order to be grandfathered under earlier solar policy.  Basic rates have increased and net metering was eliminated, replaced by a fixed purchase rate that starts at $0.129 per kwhr and will decrease in the future.  Further details are posted in a link below.

Quick APS Links:

News Release (Aug. 15, 2017)
Summary for Residential Customers
Summary for Business Customers
Solar Grandfathering Fact Sheet (also see the note below for additional information)

The Arizona Solar Center has put together an unofficial summary of the new APS rate schedules for new solar customers, click here.

On August 21st APS emailed the following information to Stakeholders (but it does not seem to be on the APS website):


The Arizona Corporation Commission (ACC) has approved a decision in our rate review, and we are happy to share some details with you affecting our solar customers. We appreciate your support in delivering this message to customers and will be glad to help you with any questions you may have. For your reference, attached are letters that were sent to customers regarding grandfathering. Other resources are available at aps.com/gosolar.


  • Current solar customers that are interconnected to the APS grid will remain grandfathered for 20 years from the date of interconnection.
    • The grandfathering stays with the premise. Systems transferred to a new premise will require a new application, and the customer would no longer be eligible for EPR-6.
    • Over the terms of the grandfathering period, a customer may not increase the capacity of their grandfathered solar system by more than a total of 10% or 1 kW, whichever is greater.
  • Customers who submit a complete application by 11:59 p.m. August 31, 2017 will be eligible for grandfathering. The system would need to be installed and have AHJ approval by February 28, 2018 in order to qualify. A complete application includes all of the following:
    • Customer Application
    • Executed Contract
    • Disclaimer
    • Consumer Acknowledgement
    • Installer Application
    • Three Line Diagram
    • Site Plan

Public Meetings:

Green Building Lecture - Economic Value of Green: Knowledge is EmPOWERing

Scottsdale’s Green Building Lecture season kicks off with a panel of industry leaders on the economic value of green. 
These free programs run from 7 to 8:30 p.m. on the dates listed below at the Granite Reef Senior Center, 1700 N. Granite Reef Road. RSVPs are not needed.

Green Building Lecture Series

Solar Energy and Battery Storage Systems

Date: Thursday, Dec. 7

Time: 7 - 8:30 p.m.

This is an exciting time for renewables and on-site energy storage systems as solar continues to take off in the valley. Just this year, Scottsdale has had a record year with more than 500 residential solar electric installations and a growing number of battery storage system installs.  

ASU Senior Sustainability Scholar Paul Hirt will discuss the solar energy revolution, why solar is coming faster than anyone expected and how it will change our world. His current research includes a history of electric power, transition to renewable energy, and collaborative interdisciplinary research on water use, urban growth and sustainability.

Titan Solar Power Director of Business Development Jack Walker joins Hirt. He’ll discuss residential battery storage options for utility-connected solar photovoltaics systems. Walker is set to address homeowners’ concerns about time of use rates, controlling demand charges and having a backup system in the event of a utility grid failure. For some homeowners it’s about control over time of use rates, for others it may be about controlling demand charges while for others it may be about having a "back up" system in the event of utility grid failure.

For more information see the 'Next Lecture' section of this link: http://www.scottsdaleaz.gov/green-building-program

The  scheduled lecture series includes:

  • Feb. 1, 2018 – Living an Edible Landscape Life
  • April 5, 2018 – Building with earth and Mass in the Desert 
  • June 7, 2018 – Heating and Cooling with Ductless Mini-Splits

Further information on this worthwhile program

General News feed

Caution- News leads open in new windows. Warning- These news links are automatically generated by others such as Google News and are not reviewed by the Arizona Solar Center, Inc. We are not responsible for link content.

Our Twitter Feed

azsolarcenter "A lie gets halfway around the world before the truth has a chance to get its pants on.” --Winston... https://t.co/YZUiXLzsKz
azsolarcenter The Sun Day Blog: The future is not what it used to be. In the aftermath of the 2016 election, the question has... https://t.co/lSR5RFewJm
azsolarcenter Novermber 5, 2016 -- APS, pro-solar group together spend $6 million on Arizona Corporation Commission races: The... https://t.co/5xyq4EsoFm
azsolarcenter November 3, 2016 Solar Battles Playing Out On Arizona Ballot This Election: It may not be at the top of the... https://t.co/uYSRxv97YR
azsolarcenter November 4, 2016: Utility spends $3.5 million to keep Arizona Corporation Commission all-GOP: The state’s largest... https://t.co/imqk6z2sDU
azsolarcenter October 25, 2016: 42 States (and DC) try to screw with solar The 50 States of Solar Policy Report by the NC... https://t.co/JBYTzpf2ui
azsolarcenter October 24, 2016 -- Future of independent solar energy at stake in Corporation Commission raceL The long-term... https://t.co/D6jy4I5Ci0
azsolarcenter October 13, 2016 -- State policy matters: It is very easy to get distracted by the dog-and-pony show of this... https://t.co/MH7mEMg9MC
azsolarcenter October 16, 2016: Arizona Corporation Commission DebateL Five candidates running for three open seats on the... https://t.co/tm0XLl6CqG
azsolarcenter My Sun Day blog is posted to the Arizona Solar Center. https://t.co/vRrxwSSQpw
azsolarcenter There is No Plan(et) B: Climate change is no longer an issue that our politicians can kick down the road for... https://t.co/KHZzajZc9K
azsolarcenter High Noon: Nearly 40 years ago, President Carter proclaimed the dawn of the solar age. If President Carter was... https://t.co/JmZSHlmBUI
azsolarcenter High Noon: Nearly 40 years ago, President Carter proclaimed the dawn of the solar age. If President Carter was... https://t.co/rBgkaWKDs6
azsolarcenter High Noon: Nearly 40 years ago, President Carter proclaimed the dawn of the solar age. If President Carter was... https://t.co/RzXaQACpPR
azsolarcenter High Noon: Nearly 40 years ago, President Carter proclaimed the dawn of the solar age. If President Carter was... https://t.co/t1fKNTPwIB
azsolarcenter High Noon: Nearly 40 years ago, President Carter proclaimed the dawn of the solar age. If President Carter was... https://t.co/dWEKk3QR6H
azsolarcenter High Noon: Nearly 40 years ago, President Carter proclaimed the dawn of the solar age. If President Carter was... https://t.co/y4vhOpjfh1
azsolarcenter September 29, 2016: To cover a utility's fixed costs, are demand charges or time-of-use (TOU) rates superior?... https://t.co/RgneQWNKyM
azsolarcenter September 25, 2016: Arizona Public Service not only rejected an Arizona Corporation commissioner’s request to... https://t.co/iip6RwoOOS
azsolarcenter September 22, 2016: The Salt River Project (SRP) board of directors has agreed to purchase energy produced by... https://t.co/xYegEuiI43
azsolarcenter September 18, 2016: UniSource Energy officials have shelved plans to use of land surroundingMohave Community... https://t.co/eXmHxo03wQ
azsolarcenter September 13, 2016: The city of Sedona spent about 90 minutes at its September 13 council meeting discussing... https://t.co/LHV2QcsvYt
azsolarcenter September 15, 2016: New solar research projects at Arizona State University will receive $3.75 million in funding... https://t.co/N20NYLWxGy
azsolarcenter September 25, 2016: The parable of the frog and boiling water is hundreds of years old. It has been used... https://t.co/O5PYqvxIJg

Thoughts on utility and Solar/Wind issues in Arizona- June 2017

Recent advances in batteries and pending changes in utility policies and rates regarding solar electric (photovoltaic or PV) systems has shown a need for background data.  The Arizona Solar Center has prepared this report. 

Most residential electric utility customers do not understand the challenges that utilities face with adapting and accommodating renewable energy.


Electric utility operations

 The need for electrical power varies by:

  • Time (seasonal, time of day, instantaneously as equipment cycles no and off, etc.) (see Need for Storage later in this document)
  • Location (rural vs. urban)
  • Type of equipment (lights, water pumping, smelting, heating/air conditioning, water heating, vehicle charging, etc.)

 This varying demand for electrical power is always a challenge for utilities, and a direct cost.  Many types of electrical generator cannot vary their output quickly (nuclear and hydro are examples), while others such as gas turbines can be varied and are used to match utility load to generation.  Utilities spend considerable effort predicting loads and managing their resources in order to meet but not exceed the demand. Some generation sources, such as solar and wind will be by their nature intermittent (since the sun does not shine at night) and their absence will have to compensated by use of other resources. The challenge also includes minimizing the cost, the larger power plants that react relatively slowly have the lower cost per kWh (kilo-Watt-hour, the usual measurement of electrical energy).

 The penalty for failure to match demand with generation is severe, outages and brown-outs (lower than normal voltage) can occur.  

 The ideal situation for a utility is constant demand, but that is not likely.  The utilities have few tools available to them to encourage an easier to manage, more constant load.  These include:

  • Rate schedules that offer lower rates during periods of generally lower demand, and higher rates during periods of generally higher demand,
  • Offering customers the availability of rates with a demand charge, but lower energy charges in order to have customers even out their energy usage,
  • Offering incentives to customers to allow the utility to turn off some loads remotely when the utility is experiencing loads in excess of the available generation (water heaters, air conditioning, some commercial processes to name a few),
  • Limiting the generation of power by sources that can more easily be cut back (large scale photovoltaic systems and most wind turbines).

 Over decades the rate schedules in Arizona have been developed in order to somewhat balance the competing demands of the various classes of customers and the related legal situation.  In Arizona the utilities have defined service areas and must service all customers on an equal basis.  Rural customers generally cost more to serve than urban customers.  Small customers cost more to serve than large customers, on a cost per KWH basis.

 Due to many reasons, it is not practical to directly allocate utility costs to customer bills.  Kind of related to the old economic impossibility of calculating the relative costs of steak, tallow, hide, etc. of beef when the costs are related to raising the whole animal.  These economic problems are best solved by letting the market place establish the relative prices based on supply and demand.  While the prices of commodities can vary quickly, few power users would be well served by waiting for a utility to determine actual costs before billing users.   

In a perfect economic situation, a utility customer would be billed for electric services in direct accordance with the cost of providing the services.  The basic services are the energy generation and the transport of the energy to the customer.  The transport involves the requirement for equipment to carry the peak power requirement of the customers and is called “Demand”.  Precise billing is not possible for many reasons because of the interplay of fixed and variable costs and the complex issues involved.  To address this billing need, easy to implement rate schedules have been developed for the many classes of customers and for many reasons.  These rates attempt to match costs with pricing for various classes of customer.  As an example, APS presented the following comparison of Cost structure vs. Revenue Collections for residential customers:

Another way of looking at this:

One consequence of this method of billing is that a utility recovers most of its residential fixed costs on the basis of residential customer energy use.  As a result, when a customer reduces the energy used by installing a PV system or solar hot water system, the customer’s contribution to the fixed costs decreases, but there is not a proportionate decrease in the utility fixed costs.  When DG (Distributed Generation) is a small portion of the utility energy mix, this imbalance is insignificant compared to the costs and problems involved in modifying the overall utility rate structure to better match revenues by customer class with the costs of serving the customers. The above APS illustration (other utilities are similar, but APS has provided a good graphic representation at a metering workshop) illustrates the mismatch.

This is the overall result of literally dozens of rate structures that are available to APS residential customers that range from fixed flat rates (energy not charged for such as street lights) to billing based on energy used and demand by time of use.  While the revenue values are accurate, the allocation of costs between residential and commercial customers is not an exact science, but this is close.  The variable revenue is based on both energy consumed and demand charges that reflect the peak loads imposed on the utility and the amount of equipment required to provide the energy.

 The obvious question is ‘Why do these percentages not have a closer match?’  There are hundreds of reasons ranging from the need to provide universal service to customers within the service territory to a political need to treat some customers differently.  That is beyond this discussion.

 The proportion of fixed and variable (energy and demand) customer charges in a rate is of high interest for DG (Distributed Generation- such as customer PV systems) because DG sources reduce variable charges.  The variable part of a utility rate includes Energy (measured in kilowatt-hours) and peak demand (measured in kilowatts).  Peak demand is reflective of customer “usage” or “burden” on the utility distribution system. 

Impact of DG

As renewables such as solar and wind become more significant in the mix of generation resources in Arizona, they will affect how each utility addresses the operational and revenue issues.  Solar and wind bring both benefits and challenges into the generation and usage related issues in operating a reliable utility system (a legal requirement placed on the utilities).  A customer benefit may be a challenge to the utility.  Society as a whole benefits when the environment is improved, but is this benefit reduced if the utility reliability is reduced? 

DG brings many benefits to the Utility; PV systems help utilities avoid the most expensive power for much of the afternoon, save costs of adding infrastructure (customers make the investment), and reducing loading on transmission lines. 

The overall discussion of the costs of solar vs. benefits of solar are beyond the scope of this report.

The need for Storage

 In commercial-scale electricity generation, the ‘duck’ curve is a graph of power production over the course of a day that shows the timing imbalance between peak demand and renewable energy production.

The dip in this curve, increasing in proportion to installed solar capacity, illustrates the utility problem in meeting demand in the early evening.  Energy storage can be used reduce the ‘head’ by transferring energy from daytime to evening. 

The role of storage 

The concept is simple, but expensive to implement- Store excess energy from periods of low demand relative to energy availability, and use the energy during peak times. The storage can be batteries, pumped water, compressed air, etc.  There is both a value and a cost with using energy storage.  The value of storage in a utility connected situation depends highly on the usage pattern and the selected utility rate schedule.  Taking APS bundled standard residential summer rates (May 2017, subject to change in a few months) as an example: 


On-Peak period

$ per kWh

$ per kW








$ 0.24477

$ 0.06118

No demand charge



$ 0.08867

$ 0.04417

$13.500 per On-Peak kW


Before considering homes with PV systems, the possible effect of storage on energy costs is as follows:

  • Under TIME ADVANTAGE storage can be used to shift Off-peak energy worth $ 0.06118 per kWh to On-peak periods when the energy is worth $ 0.24477 per kWh, a savings of $0.18359 per kWh.
  • Under the COMBINED ADVANTAGE rate, the energy cost savings is only $0.0445 per kWh, but proper usage of storage during On-peak periods can reduce demand charges by $13.500 per On-Peak kW. Savings depend on using the storage when it produces the most savings. 

 Under TIME ADVANTAGE if the lifetime cost of the storage is less than $0.18359 per kWh, then there is a savings.  It is difficult to calculate this lifetime cost because storage (typically batteries) life depends on many variables such as depth of discharge, ambient temperature, cost of the capital involved, etc. (Estimate the cost per kWh shifted by dividing the cost of the battery system by the total number of kWh that will be shifted over the life of the battery) 

Under COMBINED ADVANTAGE it is far more difficult to project savings that will be mostly due to reducing the demand charges.  Most utility customers who select the COMBINED ADVANTAGE rate will take steps to either manually or automatically reduce demand.  Manually includes changes in life style such as limiting high energy use during the peak periods (A/C off, water heater off, no baking, etc.) or automatically with a device called a load controller.  While it is easy to look back and see when peak usage occurred and when storage could have been used, it is very difficult on an instantaneous basis to determine when to commit limited storage to reduce monthly demand when a future period may occur after the battery has been discharged.  Some companies are providing an internet ‘cloud’ service wherein a computer learns usage patterns  and applies services such as weather forecasting and utility rates to determine the most likely period of high demand and when to us any available storage.  The same process is used to recharge the battery with lower cost energy. 

Adding PV to the analysis 

If a home has a PV system, the foregoing analysis is more difficult and depends on the relative sizes, and the utility policy for instantaneous excess local generation (net metering, etc.).  The following discussion assumes net metering and the APS EPR-6 rate (soon to be modified).  Under the current May 2017 net metering policy an APS customer using TIME ADVANTAGE or COMBINED ADVANTAGE rate plans will have essentially two net metering accounts, On-peak and Off-peak.  Any excess generation remaining on either account is credited at $0.02868/kWh (off-peak) or $0.02943/kWh (on-peak) at the end of the year.  Any excess on-peak kWh cannot be used to meet off-peak usage.  If the relative size of the PV system results in excess off-peak energy and a need for on-peak energy, storage may be carefully used to shift some off-peak energy to on-peak periods.  This has to be done carefully as shifting too much may result in an annual surplus in the on-peak account that is worth only $0.02943/kWh. 

Some families have adapted well to TIME ADVANTAGE, such that a PV system that faces South to West and is sized to produce only 65-70% of the annual usage will produce 100% of the on-peak energy.  This means that any increase in PV system size will only serve to produce excess on-peak energy worth only $0.02943/kWh and off-peak energy worth $0.06118/kWh.  It is difficult to justify the cost of storage in such a situation. 

Private storage vs. Utility storage 

In theory, utilities could use high capacity storage to shift vast quantities of energy in order to level the balance between generation and demand.  At present (May 2017) utility scale storage is still in the research mode. Tucson Electric Power (TEP) is testing a 10 MW , 4-hour battery and SRP plans on testing a similar system.  APS has a few feeder storage systems (2 MW).  When and if such storage becomes economically viable, it will be more cost effective than local customer storage. 

Residential solar users considering adding battery storage to their PV system need to consider if the additional cost of a battery system will produce savings that justify the additional investment. Since future utility rates (On-Peak, Off-peak, excess, demand as per the earlier discussion) are not well defined, the exact savings cannot be calculated. 

Cutting the cord?

 Some advocate having a home PV system with storage that is large enough to disconnect from the utility.  For most families, this is simply not economically practical.  Residential energy needs have a summer and a winter peak (low spring and fall usage).  The winter peak corresponds with lower levels of sunshine (and longer periods of cloudy weather).  A careful analysis of expected worst case PV system output on a monthly or even daily basis vs. the expected energy needs will determine the required system component sizes and the costs.  This also means that any excess PV output that exceeds storage will have to be controlled by regulating equipment (simply disconnected) as seasonal energy storage is not likely to be practical. A reliable standalone PV system may cost more than the residence, if it can be installed on the property.

Renewable Energy: An Overview - The Greenhouse Effect

Ninety-three million miles away, the sun blazes energy toward Earth. When this energy reaches Earth, the energy transmitted in short wave-lengths (visible light, ultraviolet, etc.) penetrates our atmosphere and strikes the Earth's surface. Energy in long wavelengths (such as infrared, thermal radiation or heat) is absorbed by carbon dioxide and other gases in the atmosphere. When penetrating short wavelengths strike Earth, they are converted into long wavelengths (in the form of heat radiation) and reflected back toward space. Some thermal radiation escapes, but most of it remains trapped inside our atmosphere. These long waves build up and keep Earth warm. This phenomenon, known as the greenhouse effect, enables life to flourish on Earth.


Its future effects are also the subject of much discussion.As carbon dioxide and certain other gases increase in the atmosphere, more and more of the heat that should escape and radiate into space remains trapped. This trapped heat is the subject of debate within the scientific community. Scientists, lined up on each side of the issue disagree as to whether this heat may cause a rise in global temperatures.

According to the late Carl Sagan, a world-renowned environmental author, the typical global temperature difference between an ice age and an interglacial period is three to six degrees Celsius (5 degrees to 11 degree Fahrenheit). Sagan theorized that if global temperatures were to rise three to six degrees C, water would become warmer and expand, melt polar ice caps and raise sea levels. Under these conditions, many islands would disappear and the oceans would flood such coastal cities as New York, Los Angles and Tokyo. Just a three-foot rise in sea level would triple the size of San Francisco Bay.

Global warming may change precipitation patterns as well. Rainfall could decrease in some areas, causing water shortages and failing crops, while increasing in other areas with attendant flooding and soil erosion. Plants and animals that do not adapt quickly to the changing environment could become endangered species.

Some scientists, however, believe that an increase in global temperature could result in increased crop yields. Higher carbon dioxide levels associated with global warming could be beneficial for plants. If carbon dioxide levels doubled, it is theorized that plants could improve productivity by as much as one-third. Some evidence shows that a rise in carbon dioxide could increase a plant's optimal temperature and allow plants to thrive in warmer temperatures.

Those that subscribe to the greenhouse theory and global warming believe the primary cause of global warming is high emissions of carbon dioxide from industrial processes and the burning of fossil fuels. The U.S. is the world's largest carbon dioxide emitter. The greatest amount of carbon dioxide emitted comes from burning oil, coal and natural gas to produce the electricity that maintains the American standard of living. Transportation is the second largest contributor to the problem. Each car in the United State emits more carbon dioxide per year than the weight of the car.

Some models used by scientists support the theory that an increase in atmospheric carbon dioxide produces global warming. Scientists have been making attempts to measure any difference in global temperature. Researchers at NASA as well as other scientists believe there has been a 0.5 degree C (0.9 degree F) increase in the average global temperature over the last 100 years. Other scientists remain unconvinced. Researchers using the TIROS-N weather satellite to measure the temperature of the lower portions of the atmosphere during the 1980s did not find any detectable warming.

Despite the controversy over whether the global temperature is rising, the greenhouse effect is a well-established theory in atmospheric science. For example, Venus has a dense carbon dioxide atmosphere that could account for its surface temperatures of 426 degrees C (800 degrees F). Mars, with a thin carbon dioxide atmosphere, has an average temperature of -53 degrees C (-63 degrees F). This temperature difference, however, may also be partially explained by the distance of these planets from the sun.



APS STAR Center redeployed
(December 2011, text provided by APS)

For the last 25 years, the Solar Test and Research (STAR) Center is where Arizona Public Service has worked with manufacturers, universities and government labs to propel technological advancements in converting solar energy into electricity. The goal? To find technologies that would allow solar energy to become a viable resource option for customers.

Success on that front means the STAR Center takes on a new role.

Personnel and focus have transitioned from technology research to solar operations and maintenance. The chief focus is to provide cost-effective support to ensure optimal system production and research the long-term reliability of our solar investments.

Today, more than 21,500 megawatts of solar have been developed globally, with APS having more than 500 megawatts either online or in development. Manufacturers the world over produce roof-integrated tiles; mono- or poly-crystalline photovoltaic panels; solar box ovens; evacuated tube collectors and glazed flat plate collectors; hybrid solar-thermal systems; hybrid solar lighting systems; solar pumps, fans, and switchable windows; mirrors and tracking systems used in trough/parabolic mirror concentrators; and thermal storage systems. And while listing innovations, I’d be remiss not to mention the increasing deployment of passive solar design – well-known to historians and architects, but never studied on site.

This technological cornucopia has overflowed since the STAR Center opened in 1985, and innovation will doubtless continue.

Now, APS is looking to find solutions to the next set of challenges associated with renewable energy. Namely, how the intermittency from solar and wind resources affects APS’s ability to provide reliable and affordable electricity to customers.

So, while the STAR Center will no longer be open to testing and research of new solar technologies, the solar installations currently in place will remain in operation. A majority of the solar panels at STAR will continue to operate and provide clean energy to customers on the APS grid. Those panels that were removed were re-deployed to other solar projects or returned to the manufacturers.

Further, the STAR Center is now also serving as a working laboratory for those learning to install solar electric systems – or for installation companies who are pursuing continuing education opportunities. Though its mission has changed, APS STAR Center will enjoy a long future of service to APS customers and the solar industry.

Contributed by Renee Guillory, DE Partnership Manager, Arizona Public Service



Past and Present Research


High-concentration PV

PV Test Rig

80 kW PV Power Plant

Inverter Testing



  • Welcome to the Arizona Solar Center

     This is your source for solar and renewable energy information in Arizona. Explore various technologies, including photovoltaics, solar water heating, solar architecture, solar cooking and wind power. Keep up to date on the latest industry news. Follow relevant lectures, expositions and tours. Whether you are a homeowner looking to become more energy efficient, a student learning the science behind the technologies or an industry professional, you will find valuable information here.
  • About The Arizona Solar Center

    Arizona Solar Center Mission- The mission of the Arizona Solar Center is to enhance the utilization of renewable energy, educate Arizona's residents on solar technology developments, support commerce and industry in the development of solar and other sustainable technologies and coordinate these efforts throughout the state of Arizona. About the Arizona Solar Center- The Arizona Solar Center (AzSC) provides a broad-based understanding of solar energy, especially as it pertains to Arizona. Registered Read More
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