300 days of sunshine

With more than 300 days of sunshine every year, Arizona is a natural for solar power. In fact, the state was recently ranked No. 2 for total solar energy capacity. Some of the benefits of solar energy are clear. This clean, renewable energy source has no carbon emissions and uses no water.

Solar power is an important resource helping to power our customers’ lives, however, we must make sure we are getting the most bang for our buck. Grid-scale solar (large solar farms that typically contain solar panels that track the sun across the sky), in a direct comparison, produces more, costs less and helps the environment far more than private residential rooftop. In addition, grid-scale solar means all APS customers are solar customers, not just the ones who can put panels on their roof.

For the past five years, Arizona Public Service (APS) has been hard at work overseeing the construction, maintenance and delivery of solar energy from nine solar plants around the state that are part of our AZ Sun Program. All but one of these plants has hundreds of thousands of panels that rotate to face the sun, enabling them to capture the power of the sun far more hours of the day than rooftop, including late afternoons when our customers need the most energy.

That’s why, for an equal hypothetical $20 million investment, grid-scale solar in Arizona could generate 28,500 megawatt-hours (MWh) in a year, compared to residential rooftop at just 12,400 MWh. Using the same example, when it comes to environmental impact, grid-scale solar avoids a whopping 25.6 million pounds of carbon emissions in a year, while residential rooftop avoids just 11.1 million pounds.

Water savings from grid-scale solar are 8.9 million gallons per year, while residential rooftop saves just 3.9 million gallons. And as we desert-dwellers know, maximizing water savings is critical to our future.

The overwhelming, evidence-based consensus, according to recent reports from MIT, Harvard and the Brattle Group, confirms that grid-scale solar power generation is more cost-effective than rooftop. Put another way, both grid-scale solar and rooftop solar could achieve the same environmental benefits, but the cost to do so with grid-scale solar would be much lower.

Why does grid-scale solar cost less and operate more efficiently? Three reasons. Perhaps the most obvious has to do with the economies of scale gained by building a plant with thousands of panels, as opposed to the average residential rooftop. These large scale solar plants can be optimally situated in areas of peak sunshine, not wherever a home happens to have been built. As mentioned earlier, the technologies used at grid-scale solar plants incorporate optimized panel placement and sophisticated tracking mechanisms so panels move to face the sun throughout the day.

At APS, we understand how important solar is to our customers and to our state. We also understand the importance of the environmental benefits solar power brings. Our question is: Why pay more for the same sun?

— Tammy McLeod is vice president of resource management at Arizona Public Service.

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