Hold rate
The share of people who started a video and were still watching at a meaningful point.
Commonly measured as fifteen-second views over three-second views, or as completions over starts. Hook rate says whether the opening worked; this says whether the rest did.
Why it matters for HVAC
The two failures need different fixes and look identical in a cost per lead. A strong hook with a weak hold means the opening promised something the video did not deliver, and the answer is editing rather than reshooting. A weak hook with a strong hold means good content nobody is reaching, and the answer is the first second.
For longer explanatory content, which works well in this trade, hold rate is the metric that tells you whether explanation is welcome or whether you are talking past the viewer.
How it is measured
Within an ad set, over the same period. Read it beside hook rate, because either number alone points at the wrong repair.
A worked example
A three-minute video explaining how system age affects running cost: hook rate 11%, hold rate 62%. Very few people start it and most who do watch nearly all of it. Recutting the first five seconds to lead with the running-cost figure takes the hook to 26% without touching the body, and the same content reaches more than twice as many people.
These figures are invented to show the arithmetic. They describe no real business.
Where this is demonstrated
The Creative production pillar scores every listed agency on what they document here, and gives you the questions that tell you which one you are being sold.