A lot of HVAC owners avoid their profit and loss statement because it feels like something built for accountants, full of line items that don't mean much on a Tuesday afternoon between calls. That's a mistake, because your P&L is one of the few places that will actually tell you the truth about your business, if you know what to look for.

Start with revenue, but don't stop there. Revenue tells you how much came in the door. It says nothing about whether the business made money doing it. The next number that matters is cost of goods sold, which for an HVAC business means materials, equipment, and direct labor tied to the jobs you ran. Subtract that from revenue and you get gross profit, which tells you how much each job actually contributed before overhead.

From there, gross margin, meaning gross profit as a percentage of revenue, is one of the most useful numbers you can track month over month. If that percentage is sliding even while revenue climbs, it usually means either pricing hasn't kept up with rising material and labor costs, or jobs are running less efficiently than they used to.

Below gross profit sits your overhead: rent, insurance, office staff, marketing, and everything else that keeps the business running regardless of how many jobs you ran this month. What's left after all of that is net income, the actual bottom line.

The mistake we see most often is owners watching revenue climb and assuming that means things are going well, without ever checking whether gross margin and net income are actually moving in the same direction. Revenue can grow while profit shrinks, and it happens more often in this trade than most owners expect.

Reading your P&L doesn't require an accounting degree. It requires a P&L that's accurate and current, and about ten minutes a month to actually look at it with these numbers in mind.

Jeremy Brewer is the founder of 911 Bookkeepers LLC in Baton Rouge, Louisiana. He worked in the field as an HVAC tech before building books for the trades, and he serves as a licensed paramedic in EMS. He is a Xero Certified Advisor.