You've been operating for a while -- maybe for years -- and lots of things have changed since your data center was built. Maybe it was done well at the time. Maybe it wasn't. Maybe something has failed and given you a wakeup call. Maybe it hasn't yet, but you're worried it will. Regardless, a lot has changed in those intervening years. Manufacturers are more open about what's coming, so we can all plan better than we could even five years ago. (If you're designing a new data center, and it's going to look a lot like the old one, but with a little more power and air conditioning, you'd better find someone who's up to date to help!)
A good data center audit will not only uncover hidden flaws, it will tell you how far you can reasonably take this facility and will provide general guidelines as to how to do it. It will be worth its weight in batteries if it saves you from a crash by identifying risks before they happen. If nobody acts on them, at least you can't be faulted for waiting until the proverbial horse is out of the barn before saying the door should be closed.
In one audit, we cautioned that the dual power feeds were from the same local electrical grid, with no generator to cover the contingency. Our report was presented to management just two days before the massive grid failure hit the Northeast, originating in that exact grid. The IT folks who had asked for the audit looked real good at that point and got their budget approved as soon as the lights came back on. Just a few days later they would have been regarded as no more than "Monday morning quarterbacks," regardless of the fact they had started the audit process weeks before. No one would have believed that kind of forethought wasn't inserted in the report after the fact!
As with everything, audits can be done well, or they can be little more than sales tools for services. Beware the "free" audit or the review that's too cheap. Doing this right can take several days on site and several more days compiling data, plus the time to write a meaningful report. The report should be tailored to your business, your facility and your particular problems and concerns, not a "canned" checklist and "file drawer" paragraphs. Ask to see a couple of reports before contracting and see if they're individual or if they look like "boilerplate" copies with different names. Data centers have a lot of things in common, but they are also each unique to the needs and circumstances of their companies. Also look at recommended solutions. Are they practical, or are they a list of "ideals" that could never be realistically implemented? You're going to pay for this study one way or another. You should get your money's worth in real advice.
A good audit will involve IT, facilities, a local electrician and your electrical and mechanical engineers if you have professionals you usually work with. Some engineering firms have the specialists on staff to conduct a good data center audit. Most do not. In any case, you'll get a better job in less time if the people most familiar with your installation are fully involved.