Pentair plc's (NYSE:PNR) price-to-earnings (or "P/E") ratio of 20.4x might make it look like a sell right now compared to the market in the United States, where around half of the companies have P/E ratios below 17x and even P/E's below 10x are quite common. Although, it's not wise to just take the P/E at face value as there may be an explanation why it's as high as it is.

Pentair certainly has been doing a good job lately as its earnings growth has been positive while most other companies have been seeing their earnings go backwards. The P/E is probably high because investors think the company will continue to navigate the broader market headwinds better than most. You'd really hope so, otherwise you're paying a pretty hefty price for no particular reason.

What Are Growth Metrics Telling Us About The High P/E?

There's an inherent assumption that a company should outperform the market for P/E ratios like Pentair's to be considered reasonable.

Retrospectively, the last year delivered an exceptional 33% gain to the company's bottom line. Pleasingly, EPS has also lifted 40% in aggregate from three years ago, thanks to the last 12 months of growth. So we can start by confirming that the company has done a great job of growing earnings over that time.

Turning to the outlook, the next three years should generate growth of 11% per annum as estimated by the analysts watching the company. Meanwhile, the rest of the market is forecast to expand by 11% per year, which is not materially different.

In light of this, it's curious that Pentair's P/E sits above the majority of other companies. It seems most investors are ignoring the fairly average growth expectations and are willing to pay up for exposure to the stock. These shareholders may be setting themselves up for disappointment if the P/E falls to levels more in line with the growth outlook.

What We Can Learn From Pentair's P/E?

Generally, our preference is to limit the use of the price-to-earnings ratio to establishing what the market thinks about the overall health of a company.

Our examination of Pentair's analyst forecasts revealed that its market-matching earnings outlook isn't impacting its high P/E as much as we would have predicted. When we see an average earnings outlook with market-like growth, we suspect the share price is at risk of declining, sending the high P/E lower. Unless these conditions improve, it's challenging to accept these prices as being reasonable.

Before you settle on your opinion, we've discovered 1 warning sign for Pentair that you should be aware of.

If these risks are making you reconsider your opinion on Pentair, explore our interactive list of high quality stocks to get an idea of what else is out there.

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