“Buyer beware” is always a good rule of thumb when weighing some “deal” that seems too good to be true. But it should be “taxpayer beware” or “ratepayer beware” when the “deal” in question involves a solar power system, since the bargain being offered often involves pilfering from one pocket (taxpayers) to fill another (solar power companies).

The Taxpayers Protection Alliance (TPA) has been doing extensive research into the shadier side of solar energy. And one of many questionable practices we’ve seen is how some politically-connected solar companies have found sly ways to pocket tax credits for themselves that should be going to their customers. Here’s how the “deal” works.

These companies discovered that if they lease rooftop solar systems, rather than sell them outright — something that appeals to homeowners confronted with the steep up-front costs of such systems — the companies themselves can claim the federal tax credits, as well as all state and local incentives that are being offered. They’re sometimes double- and triple-dipping, raking-in taxpayer money not just from Washington, D.C., but from state or local governments that offer subsidies. They’ve tapped a steady stream of taxpayer dollars to keep themselves afloat. And their growing army of lobbyists won’t surrender that revenue stream willingly, meaning the funds could keep flowing long after this industry should be standing on its own.

The dollar figures involved are potentially huge, given the fad-like status solar energy enjoys. For example, California’s Go Solar California! campaign, a “joint effort of the California Energy Commission and the California Public Utilities Commission,” recently found that the California Solar Initiative has cost state taxpayers there more than $1.5 billion.

One recent news report indicated that SolarCity received “over $400 million in cash from the state and federal governments,” plus commissions from the financing the company arranges for homeowners.

But California is only one market in which SolarCity plays. It’s here in Arizona, too, and will go wherever its “business” model is backed by generous subsidies and helpful government mandates. What happens when the subsidies stop, or the market-creating mandates go away, isn’t a question enough people are asking.

We’ve all seen how easy money and government interventions (even when arguably well-intended) can create “bubbles.” We know how badly things can go when bubbles burst. It very much appears as if government subsidies and mandates are creating a solar bubble, by propping-up an entire industry that could implode once those supports are withdrawn. Despite its diversion of tax dollars, and New York State’s recent promise to build the company a $750 million factory, SolarCity is posting big losses and has some industry analysts jittery. Yet the promise of future government revenue, and the confidence that it will enjoy favorable treatment from political friends, has the company undertaking a massive expansion.

Companies that take such chances with private funds are one thing: companies that use public funds for risky ventures are another, since non-customers and taxpayers are effectively enabling such bubble-inflating behaviors. This means taxpayers are propping up a company that is arguably taking advantage of consumers, who will also be left in the lurch if the scheme falls apart — all to bankroll the expansion of an energy technology that, despite all the hype, still meets a relatively tiny share of America’s overall energy needs.

Who’ll pick up the pieces if the solar bubble bursts? Who picked-up the pieces when the housing bubble burst?

Investing in solar power is fine, when private dollars are spent and risked. But when public funds are used, we all have a right and an obligation to take a harder look at what these companies are doing with that money.

• Sean Paige is a senior fellow with the Taxpayers Protection Alliance (www.ProtectingTaxpayers.org).