Shares in engineering company Renishaw (LSE: RSW) have fallen by over 10% today after it released a profit warning. It now expects sales for the full year to be in the range of £420m to £440m, with pre-tax profit due to be between £67m and £83m. Although Renishaw had already made clear that the current year would see a fall in revenue versus last year due to the lack of large orders from the Far East, today’s update indicates that operating conditions are much more challenging than had previously been anticipated.

While this is disappointing, Renishaw’s track record of profitability has been relatively volatile. In other words, it’s not an especially stable company, so ups and downs regarding its bottom line are perhaps to be expected. However, with its shares trading on a hefty premium to the wider market, they could come under further pressure in the near term. For example, even after today’s fall Renishaw trades on a price-to-earnings (P/E) ratio of around 18, which indicates that it may be prudent to await a lower share price before buying-in.

Not so Mitie?

Also reporting disappointing news today was support services company Mitie (LSE: MTO). Its shares have fallen by around 9% after it stated that the company has seen revenue shortfalls in the second half of the financial year, as some work has been either delayed or cancelled as a result of increased economic pressures and uncertainty. This means that revenue will be below previous guidance, but with Mitie having effectively managed its cost base and focused on maintaining margins, it expects profitability for the full year to be within the current range of expectations.

Clearly, investors are somewhat nervous regarding the scope for further pressure on the company’s top line. As such, Mitie now trades on a P/E ratio of just 9.2, which indicates that it could be due for an upward rerating. And with the company forecast to post 6% earnings growth in the next financial year, and 7% the year after, now could be an excellent time to buy Mitie for the long term. That’s especially the case since it has a flexible and relatively resilient business model.

Power pack

Meanwhile, alkaline fuel cell specialist AFC Energy (LSE: AFC) has today released its full-year results, with its shares rising by up to 6% as a result. 2015 was a positive year for the company, with it achieving a number of key milestones such as the successful testing of 25, 51 and complete 101 fuel cell stacks, plus the completion of Milestone 10 and the POWER-UP programme.

Looking ahead, AFC Energy appears to have considerable potential to deliver improved share price performance this year. It ‘s focused on the delivery of international contracts for the deployment of its fuel cell system, while also implementing improvements to further enhance the operability of the fuel cell system. And with demand for cleaner energy increasing across the globe, interest in working with AFC Energy could be relatively high. As such, and while it remains a high-risk play, AFC Energy could be worth buying for the long term.

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Peter Stephens owns shares of AFC Energy. The Motley Fool UK has recommended Renishaw. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.