Maine entered the year with dozens of solar power projects at different stages of development, large and small, all across the state – good news for local economies, and a necessary step toward meeting the state’s aggressive goals for lowering carbon emissions.

Just a few weeks in, however, the future of many of those projects is now in question, after Central Maine Power, out of the blue, said it would require from developers costly upgrades far exceeding what the parties had agreed to, as reported last week in the Portland Press Herald.

Gov. Mills, who has asked the Public Utilities Commission to investigate the matter, is right to demand answers. Why are the additional costs just coming out now, after contracts have been signed and developers have moved forward in good faith?

And if adding solar projects now puts so much stress on the grid, how will it handle the electrified economy that is a critical component of the fight against climate change?

To meet its climate goals, Maine will have to shift away from the use of oil and gas, including for heating and transportation. With more of our lives running on electricity, we’ll need to generate a greater share of power from renewable sources – a much greater share.

Solar power is a big part of that effort, and new state laws and policies encouraging solar development are working, with projects totaling hundreds of thousands of panels planned for the next several years.

Each of those projects has to connect to the grid at some point. Before a project starts, the utility determines whether the substation and local distribution network can handle the new load. If upgrades are needed, they are the responsibility of the developer – if the costs are too high, the project may not be feasible.

But if the numbers work out, the developer and the utility sign an interconnection agreement, and the developer can move forward knowing their business plan is solid.

CMP, however, is now telling developers that the upgrades will cost much more than their contract states. The cost of upgrades for one project in Oakland rose from $250,000 – agreed to in December as part of the interconnection deal – to $9 million, the Press Herald reported. Another jumped from roughly $618,000 to $8.4 million.

A Maine Renewable Energy Association survey found more than 100 solar projects in 74 Maine communities have received revised cost estimates totaling millions of dollars.

The unexpected costs have made a mess of solar development in Maine. They put in danger millions of dollars in investment. Some projects may be canceled. Businesses and municipalities counting on the power produced by them may be out of luck.

More than that, they raise questions about whether the grid will be ready to handle all the new generation that must come our way. Experts say it’s alarming that these projects, some of them very small, would require such costly upgrades.

In her letter to the PUC, Mills asked commissioners to look not only at why CMP’s revised cost estimates are so high, but also whether the state’s utilities are up to the task of growing renewable-power generation.

The PUC should move quickly to find the answers, and to help put solar development in Maine back on track.