TAMPA — Tampa Electric Co. is making a substantial commitment to solar energy: the utility on Thursday pledged to build 600 megawatts of solar energy capability — enough to power 100,000 homes — by 2021.

The move piggybacks on a newfound push for solar by all major Florida utilities. Duke Energy Florida announced in August a plan to build 700 megawatts of solar power over the next four years, while Florida Power & Light is in the process of adding 2,100 megawatts by 2023.

"We have long believed in the promise of renewable energy," Gordon Gillette, CEO of Tampa Electric, said in a release. "We believe now is the time to add large utility-scale solar generation."

The utility — whose parent company TECO Energy is owned by Canadian-based Emera Inc. — expects to invest about $850 million in the project. While this will eventually save customers money in fuel costs, it will initially show up as about $1 extra on their monthly bills. But ratepayers won't see the change until the project is nearly complete.

As part of its deal with customers and consumer groups, Tampa Electric also pledged not to raise its base rates for four years. The Public Service Commission will vote on that by the end of the year.

The recent push brings Florida a little closer to living up to its "Sunshine State" nickname. Last year, the Solar Energy Industries Association, a nonprofit headquartered in Washington, D.C., designated Florida as the state with the third-most potential for solar energy. But at 700 megawatts installed, its capability for solar wasn't nearly so high, ranking No. 13.

The ongoing solar projects, and the fact that the state's solar marketplace has doubled within this past year, is poised to change that.

The latest promise for extra capacity means that solar will account for 12 percent of Tampa Electric's generation capacity. It currently has only 27 megawatts of solar capacity.

When it reaches it goal, Tampa Electric says it will have the highest percentage of solar for a Florida utility. For comparison, Duke anticipates solar becoming 8 percent of its generation capacity within four years.

Duke Energy strikes deal to lower customer bills, boost solar

Solar advocates welcomed the news.

"We strongly feel that solar power is good for customers by diversifying the energy portfolio and for the environment by providing low-cost, zero-emissions energy for Florida's families and businesses," said Stephen A. Smith, executive director of nonprofit Southern Alliance for Clean Energy, in a release.

One issue the utilities will need to address is storing the energy the solar arrays generate. Currently, storing solar energy is more difficult than other forms of energy. Duke, when it announced its solar plan, also invested in 50 megawatts of battery storage and research into solar storage.

Part of the impetus for Tampa Electric's new commitment, the company said, is the reduced cost of installing solar energy capabilities, as well as current federal tax credits.

The parties involved in the agreement with the utility include Florida's Office of Public Counsel, the Florida Retail Federation, the Florida Industrial Power User's Group, a consortium of hospitals and the federal government —– representing MacDill Air Force Base in Tampa.

Contact Malena Carollo at mcarollo@tampabay.com or (727) 892-2249. Follow @malenacarollo on Twitter.