A direct comparison for ecommerce stores - automation depth, segmentation, deliverability, pricing at scale and when each is the right pick. This guide is written for Store owners choosing an email and SMS platform, and everything below comes from work we do on live accounts rather than recycled theory. Skim the sections, take the numbers as starting benchmarks for your own market, and treat the checklist items as a work plan you can hand to your team or your agency this week.
What it costs
Mailchimp is cheaper at small list sizes and gets expensive as contacts grow. Klaviyo prices on active profiles and typically costs more per contact, but replaces separate SMS and review tooling. Model total cost at your projected 12-month list size, not today's.
Treat every range above as a starting benchmark, not a quote. Competition in your specific market, the current state of your website, how much production capacity you already have in-house, and how aggressive your growth target is will all move the number. The useful exercise is to work backwards from revenue: what is one additional customer worth, how many do you need per month to justify the spend, and does the plan on the table plausibly produce them?
How long it takes
Migration takes two to four weeks for a typical store: flows rebuilt, templates ported, deliverability warmed and revenue attribution verified before switching off the old platform.
Two things reliably compress timelines. The first is production volume: more genuinely useful pages and more consistent execution per month means faster results, which is why budget and speed are linked. The second is starting condition - a site with clean technical foundations and existing authority moves much faster than a new domain. Be honest about which one you are, then set expectations accordingly with whoever signs off on the budget.
What actually works
Choose Klaviyo when ecommerce revenue depends on behavioural automation - browse and cart abandonment, predicted lifetime value segments, post-purchase and win-back flows tied to product data.
Choose Mailchimp when email is mostly newsletters and light automation, and budget matters more than segmentation depth.
None of these are clever. They are the boring fundamentals executed at unusual quality and consistency, which is what separates programmes that compound from programmes that plateau after one quarter.
Whichever you pick, build the core five flows first: welcome, browse abandonment, cart abandonment, post-purchase, win-back. They usually produce most automated email revenue.
Verify authentication - SPF, DKIM, DMARC - on the sending domain during migration; deliverability problems get misdiagnosed as platform problems.
Mistakes that cost the most
Migrating flows without re-verifying revenue attribution, then comparing incomparable numbers.
Blasting the whole list immediately after migration on a cold sending domain.
Paying for advanced segmentation and never building segments beyond 'all subscribers'.
Every one of these is common enough that we expect to find at least two of them in any audit. Fixing them costs almost nothing compared with the spend they waste, so they belong at the top of the work plan rather than in a backlog.
Your next 90 days
Weeks 1-2: instrument everything first. Tracking, call tracking where relevant, a conversion definition that finance would accept, and a baseline you can defend later. Skipping this step is the single most expensive shortcut available, because without a baseline you cannot prove anything worked.
Weeks 3-8: ship the highest-leverage items from the 'what actually works' list above, in priority order, one at a time so each change stays attributable. Resist the urge to rebuild everything at once - it feels productive and it destroys your ability to learn.
Weeks 9-12: build the compounding layer - content cadence, review velocity, link acquisition, experimentation - and set a monthly review with a fixed agenda. For most ecommerce stores, automated flows generate a disproportionate share of email revenue relative to campaign sends - which is the real basis for choosing a platform.
If you would like a second opinion before you commit budget, we run free 30-minute strategy calls and will walk through your current setup using the same diagnostic we use with paying clients.
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Book a free 30-minute strategy call. We'll audit your setup and share a clear plan.