Why it matters on an HVAC site
The visit that matters most is the worst case. A homeowner with no cooling in August is on a phone, often on a weak connection, often outdoors, and the page they land on is usually a hero image with a phone number over it. That hero image is almost always the LCP element.
Emergency intent is also the least patient intent on the site. Somebody researching a system replacement will wait; somebody whose house is at 91 degrees will go back and tap the next result.
How to check it yourself
- Field data from the Chrome User Experience Report, which is what Google uses, at the 75th percentile over 28 days.
- Search Console Core Web Vitals report, which groups URLs by pattern and is the fastest way to see which template is the problem.
- Lab tools for diagnosis only. A lab number comes from one run on one simulated connection and should be labelled as lab wherever it is published.
Worked through in numbers
A contractor’s service pages report a field LCP of 4.1 seconds on mobile. The hero is a 2.9MB JPEG at 3200px wide, served at a rendered width of 390.
Exporting it at 780px wide as WebP took the file to 94KB. Adding `fetchpriority="high"` and removing it from lazy loading stopped the browser discovering it late.
Field LCP moved to 2.2 seconds over the following month. The page did not change visually in any way a visitor would notice.
Where this sits in the rankings
Scored under Technical SEO. How long the biggest thing on screen takes to appear.