Every Shopify merchant eventually hits the same budget question: you have a fixed amount to spend on retention marketing, and two channels competing for it. Email is cheap and familiar. SMS is newer and feels riskier. So where does the next dollar actually do more work?
The honest answer is “it depends on what you’re trying to do” — but the data makes that decision a lot less fuzzy than it feels.
Start With What Each Channel Is Actually Good At
Email and SMS aren’t really competing for the same job. They’re good at different things, and most of the “which one should I use” confusion comes from treating them as interchangeable.
Email is built for:
- Longer-form content — product education, storytelling, visual lookbooks
- Lower-urgency touches — newsletters, loyalty updates, seasonal content
- Higher message volume at low cost — you can email a list daily without much pushback
SMS is built for:
- Time-sensitive moments — abandoned carts, flash sales, restocks
- Short, direct asks — a single link, a single offer, a single question
- High-attention windows — most texts are read within minutes, not days
If your next campaign is urgent and needs to be seen now, that’s an SMS job. If it’s informational and can wait a day, email usually does it more cheaply.
Compare the Real Cost Per Result
Cost-per-send is the wrong number to compare. What matters is cost-per-outcome — and on that measure, the picture looks different than the sticker price suggests.
| SMS | ||
|---|---|---|
| Typical cost per message | Fraction of a cent | ~1–3 cents (varies by carrier/country) |
| Typical open rate | 15–25% | 95–98% |
| Typical click-through rate | 2–4% | 10–20% |
| Revenue per message sent (benchmark) | ~$0.05–$0.15 | ~$0.20–$0.60 |
Benchmarks based on aggregated Senderium and industry data across ecommerce accounts.
SMS costs more per message, but the revenue generated per message is typically 3–5x higher. For most stores, a dollar spent on a well-targeted SMS campaign outperforms a dollar spent expanding email volume — but only up to a point, since over-texting quickly erodes that advantage through rising opt-out rates.
Where Email Still Wins on Budget
There are real scenarios where the next dollar should go to email, not SMS:
- You have an engaged list but a small one. SMS carrier fees add up faster than email sending costs when volume is low and consistent.
- Your content doesn’t compress well. If the message needs product photos, detailed specs, or a multi-paragraph story, email carries that better than a 160-character text.
- You’re already texting frequently. Adding more SMS volume to a list you already message 3–4 times a week is more likely to raise opt-outs than revenue.
Where SMS Should Get the Next Dollar
- You have a cart abandonment problem. This is consistently the highest-ROI use of an SMS budget for ecommerce stores.
- You run time-boxed promotions. Flash sales, restocks, and 24-hour discounts lose most of their value if the audience doesn’t see them in time — which is exactly what email struggles with and SMS solves.
- Your list is smaller but highly engaged. SMS rewards quality over quantity; a smaller, well-consented list often outperforms a much larger cold email list on a per-dollar basis.
A Simple Way to Decide, Campaign by Campaign
Rather than picking one channel permanently, ask this before every campaign:
- Does this need to be seen within the hour? → SMS
- Does this need more than two sentences to explain? → Email
- Is this going to a small, highly engaged segment? → SMS
- Is this going to your full list, including less-engaged subscribers? → Email first, SMS for the follow-up nudge only
Most stores that succeed with both channels aren’t choosing one over the other — they’re routing each campaign to whichever channel matches its urgency and format, and letting the two work together rather than compete for the same budget line.
Getting the Combination Right
The stores seeing the best results typically run email as the default, always-on channel, and layer SMS on top for the moments that genuinely can’t wait — abandoned carts, restocks, and time-limited offers. That combination tends to outperform an “either/or” budget split by a wide margin.
Not sure how your current mix is performing? Senderium’s dashboard shows revenue per campaign side by side with your email data, so you can see exactly where your next dollar will do the most work — not just guess.
