eCom Buzz

Is Your Website Speed Really Costing You Sales?

A Guide to Performance ROI for eCommerce

Site speed matters—but not in the way most people think.

You’ve been told every millisecond counts. That a 100 Lighthouse score is the goal. That you’re losing money with every extra second. But in 2025, that advice is often outdated, oversimplified, or flat-out wrong.

This episode of the eCom Buzz helps you cut through the hype. Learn how to assess if your eCommerce site speed is truly hurting conversions or SEO—and when it’s safe to ignore optimization efforts. You’ll get practical benchmarks, a full tool walkthrough, and a framework to evaluate ROI before spending another dollar.

🎥 Prefer to watch the video? Check it out here

⚠️ Why Speed Isn’t Always the Problem

There’s a difference between a slow website and a slow-enough website that users leave.

Quotes like “Amazon loses 1% of sales for every 100ms of delay” are from 2006—when users were on dial-up speeds and mobile wasn’t the default. Similarly, the Walmart “2% lift per second” stat has no traceable source.

Most eCommerce stores are not Amazon or Walmart. And obsessing over load time without considering user experience, platform strategy, or conversion paths often wastes more than it saves.

The 4-Step Process for Building eCommerce Features That Work

Speed impacts revenue when it gets in the way of the shopping experience:

Pages take too long to render product details on mobile
Interactions lag at checkout
Content shifts disrupt trust

But if your site is reasonably fast, functional, and responsive on real user devices, shaving another 0.3 seconds off a PDP might not move the needle.

Focus on speed only when:

Bounce rates are high on mobile
CrUX reports show failing Core Web Vitals
Users explicitly complain about slowness

Benchmarks That Actually Matter in 2025

Use these to guide decisions—not anecdotal feelings or third-party testing tools run without context.

Metric	Good	Needs Improvement	Poor
Largest Contentful Paint	<2.5s	2.5s–4s	>4s
Total Blocking Time	<200ms	200ms–600ms	>600ms
Cumulative Layout Shift	<0.1	0.1–0.25	>0.25
First Contentful Paint	<1.8s	1.8s–3s	>3s
Interaction to Next Paint	<200ms	200–500ms	>500ms

How to Measure Real Performance (Lighthouse + CrUX)

1. Start with a User Study

Ask actual users:

“How fast does the site feel to you?”

“Did anything slow you down or frustrate you?”

Speed that feels “slow” in Lighthouse often feels fine to users.

Even a small number of interviews can uncover friction that tools miss.

➡️ Watch our full video on how to run a user study

➡️ Explore our guide to eCommerce user feedback methods

2. Check Google’s CrUX Report

This shows real-world performance data collected from Chrome users around the world. It’s more accurate than lab tests—and reflects how your site performs across devices and networks.

3. Run a Lighthouse Audit (the right way)

Open in incognito mode. Disable extensions. Emulate mobile. Use Google’s Lighthouse Score Calculator to simulate how small changes can move your score.

Performance Optimization Paths: Agile vs Overhaul

Agile Fixes (Best for Most Stores)

Identify the worst offenders
Fix one or two high-impact metrics per month
Avoid full rebuild costs
Keep momentum across UX, CRO, and SEO

Full Overhaul (Use With Caution)

Ideal for outdated stacks, heavy themes, or replatforming
Migrate to Hyvä, Catalyst, or another performance-first framework
Expect high dev hours, QA cycles, and tradeoffs

Choose overhaul only if you’re staying on the platform for 2+ years and UX is already a problem—not just speed.