Google Ads Conversion Lift Now Covers Search and Performance Max: What Ecommerce Directors Should Test Before Peak

Every ecommerce board eventually asks the same question about Google Ads: would we have made those sales anyway? Google Ads and Google Analytics 4 (GA4) can both tell you which campaigns got the credit for a sale. Neither can tell you, on its own, whether the ad actually caused it.

That matters most for the two campaign types that often take the biggest share of an ecommerce budget: Search and Performance Max. This month, Google rewrote its help page for Conversion Lift, its incrementality test, and Search and Performance Max now sit on the list of supported campaign types. In this blog, we’ll explain what has changed, why it matters for the P&L, and how to run a first test without wasting sales before peak trading.

What has changed

Conversion Lift is Google’s way of measuring the sales your ads cause, rather than the sales they get credit for. According to Google’s overview, it splits your audience into two groups: people who can see your ads and a control group who don’t. The difference in conversions between the two is the “lift”.

Until recently, the user-based version was set up for Video, Discovery and Demand Gen campaigns. The April 2026 version of Google’s set-up page told advertisers to contact their Google account representative for Display, Search, Shopping or Performance Max.

The current help page now says:

• Search and Performance Max are supported. The list covers Display, Search, Video, Demand Gen, App and Performance Max campaigns. App campaigns targeting iOS and Travel ads aren’t supported.
• There are entry thresholds. You need at least 1,000 observed conversions (conversions with supplementary data don’t count), a minimum campaign budget of US$5,000 for the study, and at least one compatible conversion action.
• It lives in your account. Studies are created from the Lift studies tab under Campaigns > Experiments.
• It reports in money, not just counts. Results include incremental conversions, incremental cost per action (iCPA), incremental conversion value and incremental return on ad spend (iROAS): the extra revenue generated per pound spent.

PPC News Feed, which spotted the change, describes it as self-serve access for Search and Performance Max, where a Google representative was previously required. Search Engine Roundtable reported it the same way. One caution: the page still opens by saying Conversion Lift isn’t available for all Google Ads accounts, so check your own account before you plan around it.

Why it matters for the P&L

Attribution answers “who touched the sale?”. Incrementality answers “who caused it?”. The gap between the two is often where budget is wasted.

• Some campaigns take credit for sales that were coming anyway. Ads shown to people already searching for your brand, or already close to buying, can look brilliant on platform ROAS while adding little.
• Others are undervalued. A campaign with modest reported ROAS may be creating demand that other channels later claim.
• iROAS is a number finance can use. It compares extra revenue with spend, so you can set it against your margin and decide whether the next pound is worth spending.
• The timing is useful. Most retailers set peak and January budgets in the next few weeks. Google itself suggests testing before major budget decisions.

A worked example

Imagine a UK homeware retailer spending £40,000 a month on Performance Max, with platform ROAS of 6. (An illustrative scenario, not a benchmark.) The board wants to raise spend for Black Friday. Instead of guessing, the team runs a four-week Conversion Lift study with a 20% holdback, covering all its Performance Max campaigns.

The result shows the campaigns do drive sales the business would not otherwise have made, but iROAS is well below the platform’s ROAS figure. The retailer still increases spend, but by less than planned, and moves the balance into the campaigns where the incremental return clears its margin.

Director checklist for a first Conversion Lift study

1. Check you can use it. In Google Ads, go to Campaigns > Experiments > Lift studies. If you can’t create a Conversion Lift study, ask your Google representative.
2. Ask one budget question. For example: “What does Performance Max add on top of everything else?” or “How many brand search sales would happen without the ads?”
3. Fix measurement first. Google recommends enhanced conversions and consent mode (ideally advanced consent mode) before launch, and runs automated diagnostics during set-up. Close the gaps it flags.
4. Test the whole group, not one campaign. Google recommends including all campaigns that share the same type, audience and targeting. Testing a subset makes lift harder to detect.
5. Agree the holdback with finance. The holdback can be 1% to 50%. Larger holdbacks give answers faster but mean more people don’t see your ads, which is a real cost in sales.
6. Run it long enough. Google allows seven days but recommends at least 14, and longer if customers take time to buy. Plan dates so the study either ends before Black Friday or starts after it.
7. Leave the campaigns alone. Normal bid and budget changes are fine. Changing creative or audiences mid-study makes the result hard to read.
8. Decide on iROAS against margin. Compare iROAS with platform ROAS and your contribution margin, record the decision, and repeat the test before the next big budget cycle.

Caveats

• Not every account has it yet. The help page still says Conversion Lift isn’t available for all accounts. Check before you commit to a plan.
• The thresholds rule out smaller stores. If you have fewer than 1,000 observed conversions, focus on clean tracking and backend reconciliation first. Google also offers Conversion Lift based on geography, which is worth discussing with your account team.
• Standard Shopping isn’t on the list. Shopping was named in the April version of the page but isn’t in the current supported list, so confirm before planning around it.
• Results come with uncertainty. Google shows a study power estimate from 50% to 95% certainty. It suggests aiming for 90%, and treating results between 50% and 90% as directional.
• It is still Google measuring Google. A lift study is far stronger evidence than attribution, but compare it with your own backend sales over the same period before making big cuts.

Final thoughts

#9/100 — Attribution tells you who took the credit. A holdout tells you who earned it.

Search and Performance Max are often among the largest lines in an ecommerce media plan, and until now most brands have judged them on numbers the platform reports about itself. A well-planned lift study gives you a better question to take to the board: not “what did Google Ads get credit for?”, but “what did Google Ads add?”.

Want help planning a Conversion Lift test, or getting your tracking ready for one? Email info@taggurus.co.uk or book a meeting today to discuss.

FAQ

Q: Is Conversion Lift the same as a Google Ads campaign experiment?
A: No. A campaign experiment compares two versions of a campaign. Conversion Lift compares people who can see your ads with a held-back group who can’t, to estimate the conversions your ads actually caused.

Q: Will holding people back cost us sales?
A: It can. Google says larger holdouts carry an opportunity cost, because the control group doesn’t see your ads. Agree the size and timing with finance before launch.

Q: How often should we run a study?
A: Google says most advertisers run about one or two a year, usually lined up with budget cycles. Run one before a major budget decision, not every month.