The bad news for American solar energy companies, and the companies that supply them, got a little bit worse on Thursday when residential solar company Sunnova Energy International (NOVA 8.70%) stock tumbled 19% (through 12:45 p.m. ET) after reporting earnings last night.

Heading into the fourth quarter of 2023, analysts already weren't terribly optimistic about Sunnova's chances, forecasting an $0.18 per share loss on sales of $223.4 million. But the news was even worse than that. Sunnova reported only $194.2 million in revenue for Q4, and a loss of $1.53 per share.

Sunnova's Q4 earnings report

Sunnova CEO William Berger described Sunnova's performance as "good," but it's hard to see how he came to that conclusion. Instead of growing as analysts had expected, Sunnova's Q4 sales contracted by about 1% year over year. The company's losses, meanwhile, ballooned by 750%.

For the year, the news was a bit better -- but still not great. Sales for 2023 came in at a healthy $720.6 million, up 29% year over year. Yet Sunnova still lost money for the year -- $3.53 per share, two and a half times worse than the company's loss in 2022.

Management blamed "an increase in interest expense, higher general and administrative expense, a write off of goodwill" for the losses, and redirected investor attention to what it calls its "adjusted EBITDA" (earnings before interest, taxes, depreciation, and amortization -- a non-GAAP figure) instead. On that metric, Sunnova's earnings looked better -- $274.5 million for the year.

Is Sunnova stock a buy after its sell-off?

Continuing the theme into guidance, Sunnova said it expects to generate between $350 million and $450 million in adjusted EBITDA in 2024 -- which sounds like a good thing. The problem is that it doesn't tell investors much about how profitable the company will be under standard earnings as calculated according to generally accepted accounting principles (GAAP).

Of further concern, management insists that by the end of 2024 it will be generating "annual cash" of "between $200 million and $500 million." It's not clear, however, if this term refers to actual free cash flow. In 2023, the company had no free cash flow at all, for example, and instead burned through approximately $2.1 billion in negative free cash flow -- nearly twice the rate of cash burn in 2022.

Long story short, Sunnova thinks it had a good year in 2023, and will have an even better one in 2024. As for me, I'm not so sure.