The U.S. Supreme Court recently took the unprecedented step of issuing a stay of President Obama's massive Clean Power Plan. The court ruled that states should not be compelled to assume the exorbitant costs imposed by the plan until a federal court determines its legality.

The ruling produced a huge sigh of relief from the 27 states currently suing to halt a large-scale transformation of their energy grid through one of the most far-reaching regulations ever imposed by the Environmental Protection Agency. Essentially, states no longer need to scramble to reduce power-sector carbon dioxide emissions by 32 percent as of 2030. Because the power plan had set interim targets in 2022, however, many states were already bracing for the costs of building new power-sector infrastructure.

Thankfully, states have been granted a reprieve. But Pennsylvania, for some reason, has chosen to move forward with the task of rebuilding its entire power-generation sector. This means the commonwealth will still undertake the construction of new grid infrastructure, including the many new transmission lines and towers needed to carry electricity from planned wind and solar assemblies.

Ironically, wind and solar technology have yet to be proven as reliable sources of power generation. Such "renewable" sources of energy are intermittent - the sun doesn't always shine, the wind doesn't always blow - and require backup power generation by coal or gas plants. So even as Pennsylvania - a state that currently derives 40 percent of its power from coal - begins to shutter its coal-fired power plants, it will need to build new coal or gas systems to backstop its projected wind and solar plants.

The question is why Pennsylvania would bear this cost when it is under no legal obligation to do so. The stay by the Supreme Court means that all compliance deadlines are now suspended, and the stay will remain in effect until the court has a chance to review the case following action by the U.S. Court of Appeals for the District of Columbia. In fact, the earliest decision from the court on the merits of the case would likely come in mid- to late 2017.

But the stay is only part of the reasoning here. More importantly, the rule could be struck down on review. Many legal observers view this as likely since the point of granting the stay was to alleviate the obligation of states to develop plans and incur further economic harm. The Supreme Court's issuance of the stay can only be read as reflecting a high level of dissatisfaction with the EPA's legal basis for the rule.

Even in the very unlikely event that the EPA ultimately prevails in court and the stay is lifted, the new compliance dates will most likely be delayed by the period of time that the stay was in effect. Or, with a new, less sympathetic administration, the entire rule could be set aside.

Apart from the costs, Pennsylvania should consider that the goals of the Clean Power Plan are of questionable practicality. While the plan, as envisaged by the Obama administration, would shut down roughly 40 percent of America's coal-fired power generation, the actual end result would only yield a theoretical reduction in global temperatures of 0.02 degrees Celsius by 2100. That may be viewed as a cost-effective benefit for Washington, but it's not for Pennsylvania.

The clean coal that currently powers much of Pennsylvania - and much of America - has proven to be durable, affordable, and reliable. Renewable energy, in contrast, has proven to be expensive and low-yield.

Pennsylvania would be wise to follow the example of those states that are rejecting the Clean Power Plan as an expensive overreach of federal authority - and one with little practical or environmental benefit.

Terry M. Jarrett is an attorney with Husch Blackwell LLP and a former commissioner of the Missouri Public Service Commission.