Best Time to Send Email for eCommerce: How to Find Yours

There's no universal best time to send email. The best time for your eCommerce brand is the one your own list proves in a test, judged on clicks and placed orders rather than opens. Hayes Media, an email and SMS retention agency for eCommerce brands, finds that hour in Klaviyo with Smart Send Time or a send-time A/B test, then schedules campaigns around it.

This guide covers how Smart Send Time works and what it needs, how to run a send-time test on one campaign, which email marketing metrics should pick the winner, and why flows don't need a send-time pick the way campaigns do. Every platform rule below is quoted from Klaviyo's or Apple's own pages, listed under Sources at the end.

Is there a best time to send email for eCommerce?

Not one that holds across brands. Your list sits in its own time zones, works its own hours, and shops on its own schedule. A chart built from other brands' lists shows when their customers clicked. It can't tell you when yours will.

Even Klaviyo doesn't hand out a universal hour. Its campaign A/B testing guide says: "If you don't know where to start, we recommend trying an evening time." That's a starting point for a test, and Klaviyo puts it right next to the option to use Smart Send Time "if you qualify".

So treat any best day and hour chart as a guess to test. We haven't quoted industry send-day benchmarks here on purpose. A number from someone else's list can't settle the question for yours, and your own results can.

How does Klaviyo Smart Send Time work?

Smart Send Time is Klaviyo's built-in send-time test for email campaigns. It runs in three stages: exploratory sends, focused sends, then an optimal send time you can reuse.

The entry bar is list size. Klaviyo's help page says: "In order to conduct the exploratory and focused tests outlined below, you must be able to send campaigns to an audience of 12,000 people or greater." Its results guide adds that "your account needs at least 12,000 active email profiles to begin testing." It's also email only: "Smart Send Time is only available for email."

Exploratory sends

In this stage, Klaviyo "tests sending times across all 24 hours of the day" and "Customers will be randomly assigned to a time during that period." Emails go out in each recipient's local time. Smaller lists need more rounds before the model has enough data. Klaviyo's table:

Lists of 12,000 to 17,999 recipients: 4-5 exploratory sends.

Lists of 18,000 to 23,999 recipients: 3-4 exploratory sends.

Lists of 24,000 to 47,999 recipients: 2-3 exploratory sends.

Lists of 48,000 to 71,999 recipients: 1-2 exploratory sends.

Lists over 72,000 recipients: 1 exploratory send. Under 12,000, the table reads "Not eligible".

Focused sends

Next, Klaviyo picks the hour with the highest engagement and checks it against its neighbours. In Klaviyo's words: "With a focused send, recipients are split into 3 groups. Each recipient receives 1 email: at the recommended send time, 2 hours before it, or 2 hours after it." Klaviyo says focused sends "continue to validate and refine that time as customer behavior changes."

Optimal send

Once the time is found, "Optimal send time can be used for audiences of any size." There's a catch. When everyone gets the email at the same local hour, there's nothing to compare, so Klaviyo "doesn't learn anything to update the Smart Send Time model or the optimal send time." If you want the model to keep learning, keep some campaigns on focused sends.

Rules that catch people out

Don't use it for deadlines. Klaviyo says: "Because we send in a recipient's local time, avoid sending time-sensitive content such as a flash sale or an announcement about an impending deadline." It also says not to run tests "around major holidays or dates that are important to your brand."

Don't stack it with an A/B test. The Smart Send Time option "is also unavailable when your campaign has an A/B test or a follow-up email enabled."

Keep your normal cadence. Klaviyo's example: "if you normally send emails once a week, you won't want to increase your sending cadence just to have the model work faster. This will skew your results."

Expect a gap between rounds. Klaviyo analyses a send only after the attribution window closes: "With the default 5-day email attribution window, this means waiting at least 5 days after the final scheduled send."

How do you run a send-time test on one campaign?

If your list is under 12,000, or you want a straight head-to-head between two slots, use Klaviyo's campaign A/B test. The steps from Klaviyo's guide:

Step 1. Build the campaign as normal, then click Create A/B test above the subject line field.

Step 2. In A/B test setup, select Test send times.

Step 3. Keep the content and subject lines of both variations exactly the same, so the hour is the only thing that changes.

Step 4. Give each variation a send date and time. Klaviyo notes: "These times use your account's time zone."

Step 5. Schedule it, then open the campaign to compare each variation's performance and its win probability.

Two details matter. First, "Send-time tests send to 100% of the campaign's recipients, so there is no remaining audience to receive a winning variation after the test." The test is the send. Second, unlike Smart Send Time, these slots run on your account's time zone, so if your list is spread across regions, each slot lands at different local hours for different people.

One test is one data point. Run the same two slots across several normal campaigns before you move your calendar.

A worked example with made-up numbers

Every number in this example is made up to show the method. None of it is client data or a benchmark.

A skincare brand sends its weekly newsletter to 30,000 people. It tests 10 a.m. against 7 p.m., with 15,000 recipients in each slot.

Slot A, 10 a.m.: 48% open rate, 1.6% click rate (240 clicks), 36 placed orders, $2,520 revenue.

Slot B, 7 p.m.: 52% open rate, 1.2% click rate (180 clicks), 27 placed orders, $1,890 revenue.

On opens, 7 p.m. wins. On clicks, orders, and revenue per recipient ($0.168 against $0.126), 10 a.m. wins. The brand picks on the metrics tied to money, so 10 a.m. leads.

It then runs the same pair on its next few newsletters. If 10 a.m. keeps winning on clicks and orders, that becomes the default slot. If the result flips back and forth, the hour isn't what's moving revenue, and the effort is better spent on the offer and the email itself.

Which email marketing metrics should pick the winner?

Clicks and placed orders. Opens are the weakest signal for a send-time test, and Apple Mail Privacy Protection is the reason.

Apple's Mail guide explains that emails can carry remote content that lets a sender see "when and how many times you view it". With Protect Mail Activity on, "remote content is privately downloaded in the background when you receive a message (instead of when you view it)." Klaviyo's A/B testing guide spells out the effect: MPP "prefetches our tracking pixel, changing the open rate data we receive on your emails", so "open rates may be inflated."

For a send-time test that's a real problem. A prefetched open is logged when the email arrives, not when a person reads it, so it says nothing about which hour your customer was paying attention. Klaviyo says it directly: "Open-rate A/B tests count recorded opens, including MPP opens, so the winning variation may reflect automatic opens as well as human engagement."

Judge the test on these instead, using Klaviyo's own definitions:

Click rate. "To calculate click rate, divide the total number of unique clicks by total deliveries." Klaviyo's blog quotes its own customer success team calling it a "true indicator of customer engagement."

Placed order rate. Klaviyo's A/B tool offers it as a winning metric, "Only available for accounts with a Placed Order metric". On Smart Send Time, check the Open Rate and Placed Order Rate per Hour graph, not just the open rate graph.

Revenue per recipient. "To calculate RPR, divide the total amount of revenue your email generated by total email deliveries." It folds clicks, conversion, and order value into one number.

Opens still have uses, like spotting a deliverability drop. Our guide to email open rate benchmarks covers how to read them now, and our piece on click-to-open rate explains what that ratio can and can't tell you.

Do flows need a best send time?

Mostly no. Flows send because a shopper did something. Klaviyo describes flows as "automated Klaviyo workflows that are set in motion by an initial trigger". The timing comes from the trigger and the delays after it, so an abandoned cart email lands relative to when the cart was left, not at a fixed hour you picked.

A day-based delay with no set time follows the shopper's own clock. Klaviyo's example: with a 1-day delay after the trigger, "the next message is scheduled for around the same time the following day as the trigger occurred."

You can pin a step to a clock time when it helps. Klaviyo's time delay offers "Delay until a specific time of day", with "Recipient's Local Timezone" as an option, and suggests it "if you know your audience typically opens emails at a certain time." That's where a campaign send-time result can carry over: to later steps in a welcome series or a newsletter-style step, rather than the first message after a trigger, where the shopper's action already set the timing. Our guide to Klaviyo email flows covers which flows to build first.

When does send-time testing not apply?

Deadline sends. Flash sales, launch drops, and last-call emails go out when the deadline says, not when a test says. Smart Send Time spreads one campaign across local time zones, which is why Klaviyo warns against it for time-sensitive content. Our Black Friday email strategy covers how to plan those sends.

Small lists. Under 12,000 recipients, Smart Send Time isn't available. A/B send-time tests still run, but with few clicks per slot, a gap of a handful of orders can be chance. Repeat the test before you trust it.

Skewed rounds. A holiday week can distort a Smart Send Time round. Klaviyo says that if results are skewed, "you can request that your historical Smart Send Time data be deleted."

Bigger problems upstream. If deliverability, segmentation, or the content itself is off, moving the hour won't fix it. An email marketing audit finds those first.

How Hayes Media sets send times for clients

Hayes Media runs email, SMS, loyalty programs, and subscribe-and-save programs for eCommerce brands. We work in Klaviyo for most accounts and have experience in most other email and SMS platforms. On send time, Hayes Media tests on the client's own list and judges the result on clicks, placed orders, and revenue per recipient, not opens.

The retention practice is "Trusted by 50+ eCom brands", with "$500M+ Client revenue driven" and "8 yrs Retention expertise". One account went from 0% to 59% of revenue from retention. Those figures and our case studies are published by Hayes on its own site. Hayes has no third-party review profile and no Klaviyo partner listing, so judge us on what an audit finds in your account.

We typically work with brands doing at least $100K per month in revenue. It's a guideline, not a gate: a smaller brand with a clear budget set aside to scale and real order volume already qualifies. One-time email projects start from $2,000 USD, and retainers for ongoing full management start from $4,000 USD per month, scoped on the discovery call. See how our email and SMS service works.

Book a discovery call and we'll audit your campaign send times, test setup, and reporting in your Klaviyo account, then show you what to test first. No onboarding fees. No lock-in contracts. No junior marketers.

Sources

Klaviyo help center, Understanding Smart Send Time in Klaviyo: https://help.klaviyo.com/hc/en-us/articles/360029794371

Klaviyo help center, Understanding Smart Send Time results: https://help.klaviyo.com/hc/en-us/articles/360041411132

Klaviyo help center, How to A/B test an email campaign: https://help.klaviyo.com/hc/en-us/articles/115005228148

Klaviyo help center, How to add a time delay to a flow: https://help.klaviyo.com/hc/en-us/articles/115003885212

Klaviyo blog, Email marketing metrics and KPIs: https://www.klaviyo.com/blog/email-marketing-metrics

Apple Support, Protect email privacy in Mail on Mac: https://support.apple.com/guide/mail/protect-email-privacy-mlhlp1205/mac