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Part of Retail media vs search ads: which drives better UK ecommerce sales?
Retail media vs search ads: which drives better UK ecommerce sales?
A head-to-head look at retail media and search ads for UK ecommerce: CPC patterns, attribution limits, and where each channel earns its budget.
What to take away
- Paid search captures demand that already exists. Retail media buys placement where the purchase decision is close to completing.
- Cost per click is not comparable across the two until billing events, placements and viewability rules are matched.
- Retail media platforms usually report attributed sales, which is an allocation of credit rather than proof of incremental sales.
- Run a holdout before moving budget, and keep the conversion definition identical on both sides.
What each channel is actually selling
Search advertising sells access to a query. You bid against other advertisers for a slot on a results page, and the auction sets the price of the click. Google Shopping and Microsoft Ads both work this way, with a product feed supplying the creative.
Retail media sells access to a shopper inside a retailer's own property. The retail media category covers sponsored products on a retailer's search page, off-site display bought with the retailer's shopper data, and screens in a physical store.
The bigger difference is who holds the record. In search, you keep query-level reporting and your own conversion tag. In retail media, the retailer holds the shopper record and you see the summary it chooses to publish.
Both channels can sell the same shopper twice in one purchase journey. That overlap is the practical reason a single reported return figure will never settle the comparison.
How the cost per click compares
A single cost per click figure hides the differences that matter. The table puts the same questions to both channels.
| Question | Paid search | Retail media on-site |
|---|---|---|
| What you buy | A click from a search results page | A sponsored placement in a retailer's search or category page |
| Who sets the price | An auction between advertisers, run by the platform | A rate card or closed auction run by the retailer |
| Signals used | Query, device, location, your own audiences | The retailer's shopper data and basket context |
| Reported outcome | Clicks and conversions recorded by your tag | Attributed sales, using the retailer's window |
| Main blind spot | Sales that would have happened without the click | Sales that would have happened without the placement |
Two cost figures are not comparable if one bills on a click and the other on a thousand impressions. Ask for the billing unit in writing before you build a model.
Attribution: why the two numbers do not line up
Paid search reports a click you paid for, then conversions your own tag recorded. Retail media reports sales the retailer matched to the placement. These are two different measurements, and neither includes a control group.
A retail media sale is an allocation of credit. A shopper who saw a sponsored product and then bought in store may be counted to that placement, while the same sale also appears in your search report.
Before treating a retail media return as proof, read the definitions behind it. Our guide to retail media return on investment explains how to label attribution as allocation and keep the arithmetic traceable.
A four-step test before you shift budget
Keep the first test small and reversible. Set the budget cap before you start, and write down the result that would make you stop.
- Write one conversion definition for both channels, covering the attribution window, whether returns are netted off, and which SKUs count.
- Pull four weeks of baseline data at the same level of aggregation, using the same SKU set and date range on both sides.
- Match like with like: brand terms against brand placements, non-brand category terms against category placements.
- Run the test with a holdout where the network allows one, then judge it on incremental sales per pound rather than reported return on ad spend.
Holdout design decides whether any of this means anything. Our walkthrough on running a retail media incrementality test sets out the split, the duration and the limits of what a single result can support.
Where the official retail data helps
ONS retail industry data gives you sales volumes and values by sector, not your campaign's effect. Use it to set a seasonal baseline and to record the release date you relied on.
If total retail sales are flat while your retail media spend doubles, the extra reported sales are more likely to be a shift between channels than new demand.
Common questions
Which is better for ecommerce, retail media or paid search?
Neither wins outright. Paid search suits shoppers who already search for your brand or category, while retail media suits products that need visibility at the moment of decision inside a retailer.
Is retail media cheaper than Google Ads?
Not reliably. On-site placement prices are set by each retailer and move with category and season, and Google Ads prices move with auction pressure. Compare cost per incremental sale instead.
Can I compare retail media return on ad spend with Google Ads return on ad spend?
Only if the attribution windows, conversion definitions and return handling match. Even then, the retail media figure includes sales that may have happened anyway.
Where does Google Shopping fit?
Google Shopping is paid search with a product feed attached. It competes for the same commercial queries as your retail media placements, so treat the two as substitutes when splitting budget.