Two more utilities in Arizona and Colorado are moving to accelerate closure of coal plants and replace them with renewable energy backed by batteries, joining a broader push in both states to shift to more cost-effective clean energy options even in the absence of state mandates. 

Tucson Electric Power on Friday released a long-term energy plan that calls for closing its remaining coal plants by 2032, on the way to 70 percent renewables by 2035. Arizona's biggest utility, Arizona Public Service, recently announced its own plan to achieve carbon-free energy by 2050, despite a lack of state mandates requiring such a transition. 

Meanwhile, Colorado Springs Utilities said it would close its remaining coal plants by 2030. Along with accelerated coal closure plans from two other Colorado utilities, this will leave multistate utility Xcel Energy, which has committed to 100 percent carbon-free electricity by 2050, the only one to keep coal plants open past the end of the decade.

Colorado wants to get half of its power from renewable sources by 2030 and 90 percent by 2050.

Arizona’s transition from coal to renewables and batteries

Tucson Electric Power’s 2020 integrated resource plan calls for a steady phase-down of its coal-fired Springerville Generating Station: The plant would start operating on a seasonal basis in 2023, close down one of its 425-megawatt units in 2027 and halt operation of the other remaining unit by 2032. 

At the same time, the plan would see Tucson Electric Power adding 1.7 gigawatts of solar, 850 megawatts of wind and nearly 1.4 gigawatts of energy storage by 2035. Alongside a big boost in its energy efficiency efforts, TEP says the plan would allow it to avoid building any new natural-gas plants. 

TEP, which serves about 430,000 customers, had already exited the Navajo Generating Station coal plant owned by Arizona utility Salt River Project, which closed down last year. It is also planning to exit the San Juan and Four Corners coal plants in New Mexico, owned by utilities Public Service Co. of New Mexico and Arizona Public Service, respectively. Both plants are in the Navajo Nation, which has asked Arizona regulators to require the utility to pay up to $62 million to compensate for resulting economic losses. 

Springerville’s remaining two units are owned by electric cooperative Tri-State Generation and Salt River Project. Tri-State, which serves 43 electric co-op members and more than 1 million people across four Western states, plans to abandon coal and add more than 1 gigawatt of utility-scale renewable generation to its portfolio by 2030.

Arizona Public Service has committed to 100 percent clean power by 2050, including an interim target of 65 percent by 2030. That target will make use of the roughly 25 percent of its capacity provided by the Palo Verde nuclear power plant, as well as 45 percent renewable energy, largely solar power. 

The Arizona Corporation Commission hasn’t imposed any clean-energy or carbon-reduction mandates on the state’s utilities, and it allowed a moratorium on new natural-gas power plant construction to lapse last year. But falling prices for solar power and lithium-ion batteries in the sun-soaked state have made that combination a cost-effective alternative to dispatchable fossil-fired power — although a fire at Arizona Public Service’s McMicken battery facility last year has halted new battery installations until the state concludes an investigation into broader safety issues. 

Colorado utilities moving toward 100 percent clean energy 

Friday’s 7-2 vote by the Colorado Springs Utilities Board approves a plan to close its 208-megawatt Martin Drake coal plant by 2023, 12 years earlier than initially planned, and to shut down its 283-megawatt Ray Dixon coal plant by 2030. 

The plan won approval by beating out alternatives that would have replaced Martin Drake’s coal generators with permanent natural-gas generation, relying instead on temporary natural-gas generators until new transmission lines can be built to replace its capacity. Under its 2020 Electric Resource Plan, the municipal utility serving about 222,000 customers will replace its 416 megawatts of coal-fired power with about 500 megawatts of new wind energy, about 150 megawatts of solar power and more than 400 megawatts of battery storage. 

Colorado Springs’ decision comes on the heels of two other Colorado utilities pledging early retirements of their coal plants. Earlier this month, the Platte River Power Authority decided to shut down its 280-megawatt Rawhide coal-fired plant by 2030, 16 years ahead of its previously targeted closure date. And in January, Tri-State said it would close its remaining units at the Craig coal plant in 2030 as part of its broader decarbonization plans. 

These decisions come as state leaders are considering a push beyond its mandate for 50 percent renewables by 2030 and 90 percent by 2050 signed into law last year. Gov. Jared Polis won the 2018 election on his call for the state to adopt a target of 100 percent renewables by 2040 and continues to press lawmakers for a more aggressive policy. 

Xcel Energy, which owns Public Service Co. of Colorado, the state’s biggest utility with about 1.4 million customers, has pledged to reduce carbon emissions 80 percent by 2030 and 100 percent by 2050; it plans to close its last two coal-fired power plants in Minnesota by 2030

In 2018, Public Service Co. submitted a plan to replace 660 megawatts of coal generation at its Comanche coal-fired power plant with 1,131 megawatts of wind, 707 megawatts of solar PV and 275 megawatts of battery storage, and won record-low price contracts for battery-backed renewables in 2018. But it hasn’t yet altered plans to keep the 750-megawatt Comanche 3 coal plant operating through 2070 or to keep the 552-megawatt Pawnee coal plant running until 2041.