Solar systems are expensive, there's no getting around that. And while individuals with the means will buy solar no matter what, people trying to make an economic case for installing solar panels on their roofs may have a hard time justifying the cost and may end up putting off the install indefinitely, even if solar prices plummet.

The reason, Brad Templeton writes, is the "The paradox of cheapening solar power":

Imagine you have an energy technology with effectively zero operating cost, like PV panels. Let’s say that it’s reached the point that it can match the price of grid power over a 20 year lifetime. That means that, if it costs $10,000, it costs $72 per month or $872 per year at a 6% cost of funds. (Since $872 buys 9688 kwh at the national average grid price of 9 cents, that means you need a 4800 watt PV system to match the grid which is hard to do for $10,000 but someday it won’t be.)

But here’s the problem? Let’s say that it’s very reasonable to predict that the cost of solar will drop by more than 9% over the coming year. That’s a modest decrease, entirely doable just with increased production, and much less than people hope from new technology. That means that your $10,000 system will cost you $9,100 to buy a year down the road. Since we are talking about a grid-equivalent price system, the cost of grid power in this example is $872. So you can buy the power from the grid, wait a year, and save money. The more you expect the price of solar to drop, the more it makes financial sense to delay. (Note that at this lower price the system is now beating the grid. What matters really is whether the dollar cost reduction of the solar system exceeds the dollar cost of the grid electricity purchased.)

Makes a good point. Luckily for the burgeoning solar industry, other motivations are at play, as is a tax cut extension.

Thanks Alex!