What happened

It's Wednesday, and the great yo-yo that is the oil market -- down so much yesterday -- is rolling back up today. As of 1:55 p.m. EDT, barrels of West Texas Intermediate crude oil due for delivery in June cost 23.5% more than they did yesterday, at $15.30 a barrel. Brent crude, the international benchmark, is up 9.1% at $22.32 a barrel.

Shares of oil companies such as Exxon and Chevron, naturally, are rising in tandem with oil prices. But companies that offer alternatives to oil are also seeing a benefit from today's pricing news. Solar-inverter maker SolarEdge Technologies (SEDG -2.66%), for example, is up a healthy 7.5%, while solar-panel installer Vivint Solar (VSLR) is racking up 11.3% gains. Clean Energy Fuels (CLNE -0.34%), whose focus is natural gas as opposed to solar power, is also benefiting from this market move, with its shares up 9.9%.

Three colorful arrows racing straight up on a black background

Image source: Getty Images.

So what

And this makes perfect sense.

After all, while some consumers choose to put solar panels on their rooftops, or buy "alternative fuel" cars in order to "save the environment," a big part of the alternative-energy market is simply consumers (and businesses) seeking fuels that don't cost as much as oil does. It stands to reason, then, that the more expensive oil gets, the more attractive alternatives to oil become -- and the more renewable-energy companies can profit by providing such alternatives.

Now what

Now here's the problem: The converse is also true. The cheaper oil gets, the less incentive there is for homeowners to pony up to put solar panels on their rooftops, or for utilities to invest in solar farms, or for companies that operate fleets of vehicles to invest in cars that run on compressed natural gas.

And while it's true that oil got more expensive today, in historical terms, $15-per-barrel crude is still awfully cheap. When you consider how volatile the oil market has been lately, up one day but down the next (and more often down than up), and how the media is reminding us every day that "the world is awash with too much oil" and that "coronavirus lockdowns on driving, flying and industrial activity have all but eliminated the need for the stuff" (says The Wall Street Journal), the clear trend that I am seeing is that cheap oil will make selling renewable energy a tough row to hoe in the near future.

So yes, renewable-energy stocks are up strongly today; investors are rejoicing, and I am one of them. (I own shares of SolarEdge.) Don't be surprised, though, if this turns out to be more of a blip than a trend. The longer oil stays cheap, the worse that's going to be for renewable-energy stocks.