TransAlta (NYSE: TAC) reported earnings on April 23. Here are the numbers you need to know.

The 10-second takeaway
 For the quarter ended March 31 (Q1), TransAlta missed estimates on revenues and missed estimates on earnings per share.

Compared to the prior-year quarter, revenue dropped significantly. Non-GAAP earnings per share shrank significantly. GAAP earnings per share dropped to a loss.

Margins dropped across the board.

Revenue details
 TransAlta booked revenue of $530.9 million. The three analysts polled by S&P Capital IQ hoped for a top line of $582.8 million on the same basis. GAAP reported sales were 19% lower than the prior-year quarter's $657.3 million.

Source: S&P Capital IQ. Quarterly periods. Dollar amounts in millions. Non-GAAP figures may vary to maintain comparability with estimates.

EPS details
 EPS came in at $0.12. The eight earnings estimates compiled by S&P Capital IQ averaged $0.20 per share. Non-GAAP EPS of $0.12 for Q1 were 40% lower than the prior-year quarter's $0.20 per share. GAAP EPS were -$0.04 for Q1 versus $0.40 per share for the prior-year quarter.

Source: S&P Capital IQ. Quarterly periods. Non-GAAP figures may vary to maintain comparability with estimates.

Margin details
 For the quarter, gross margin was 38.9%, 810 basis points worse than the prior-year quarter. Operating margin was 14.1%, much worse than the prior-year quarter. Net margin was -0.4%, much worse than the prior-year quarter. (Margins calculated in GAAP terms.)

Looking ahead
 Next quarter's average estimate for revenue is $540.4 million. On the bottom line, the average EPS estimate is $0.17.

Next year's average estimate for revenue is $2.28 billion. The average EPS estimate is $0.79.

Investor sentiment
 The stock has a five-star rating (out of five) at Motley Fool CAPS, with 87 members out of 91 rating the stock outperform, and four members rating it underperform. Among 22 CAPS All-Star picks (recommendations by the highest-ranked CAPS members), 21 give TransAlta a green thumbs-up, and one give it a red thumbs-down.

Of Wall Street recommendations tracked by S&P Capital IQ, the average opinion on TransAlta is hold, with an average price target of $18.71.

Is TransAlta the right energy stock for you? Read about a handful of timely, profit-producing plays on expensive crude in "3 Stocks for $100 Oil." Click here for instant access to this free report.