PHOENIX — What would Prop 127 do? Simply put, it would require utility companies to get half of their energy from renewable sources by 2030, regardless of the cost to you, the consumer.

And it’s that future cost that has been the subject of millions of dollars and ads.

One ad from Arizonans for Affordable Electricity claims, "127 will cost families $1,000 more per year and small businesses thousands more."

Meanwhile, an ad from Clean Energy for a Healthy Arizona alleges that Prop 127 would save Arizona more than $4 billion.

But unless you have a crystal ball, those projections are just guess work, because we don’t know the future cost of things like solar panels, fuel or even how many people will be here.

Making projections for something 12 years down the road is practically impossible.

“If you look out beyond two years in the forecast, you're probably getting into an area that is pretty well unknown,” said Rick Merritt, president of economic consulting firm Elliot D. Pollack & Company.

So as you vote on Prop 127, know that if approved, it will require companies to get 50 percent of their electricity from things like solar, wind and water—even if it may not be the cheapest way to do it.

Or it could be, but only time will tell.