Call it what it is for a second. Not "smart bidding" — automated bidding. Google sets your bids. Google, the company that makes more money every time you spend more.

You wouldn't let a salesperson on commission set your prices. But that's roughly the arrangement.

The commission structure isn't even the worst part though. The worst part is what Google does with the control once you hand it over.

The theory

Smart bidding is supposed to work like this: Google uses its signals — device, location, time of day, search history — to predict which searches are most likely to convert. Higher probability of conversion, higher bid. Lower probability, lower bid.

So you'd expect the highest bids on your most specific, highest-intent searches. Someone typing "resin driveway cost" is close to buying. Someone browsing paving ideas is not. The bids should reflect that.

They don't.

What it actually does

A resin driveway installer in Yorkshire had an account average CPC of £2.85. Google was spending up to 27 times that on searches this business would have negated on day one:

SEARCH TERM INTENT CPC monarch resin floors A competitor. Epoxy resin floors — different product, different customer entirely. £70 summit seal block paving sealer Block paving is a completely different surface material. And it's a DIYer. £57 front driveway paving ideas Someone on their sofa looking at pictures. Not ready to buy anything. £45 driveways in bicester Top of funnel. The highest CPC in the account, on one of the least qualified clicks in it. £77

A fencing company in Fairfax, Virginia had an account average of $12.84:

SEARCH TERM INTENT CPC trabajos de fence cerca de mi Spanish for "fence jobs near me." $87 fence for pool A low value job. $181 repairing fence Repair work, not installation. The client doesn't do this. $152 strong fence A brand name. Someone looking up a specific company, not shopping around. $137

A land surveying firm in Sydney had an account average of $10:

SEARCH TERM INTENT CPC customer survey platform Someone shopping for survey software. $51 duo tax depreciation quantity surveyors A competitor in a completely different field. $129 drainage surveyor A different surveying specialism entirely. $41 draughtsman sydney Different profession, different customer, different everything. $35

We see this in virtually every smart bid account we audit. It's not a glitch. It's the default.

Why the expensive clicks make it worse

Here's what you'd expect if smart bidding was working: the searches with higher CPCs should produce a lower cost per acquisition. Google's justification for bidding more is that those clicks are more likely to convert. So the maths should work out.

For the resin installer, clicks above £20 had a CPA of £117. Below £20, it was £60. The expensive clicks cost nearly double to convert. For the fencing company, CPCs above $50 produced a CPA of $159. Below $50, $136. For the Sydney surveyors, above $30 CPC the CPA was $133 — below $30, it was $61.

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Why Google does this

Google will tell you they have signals you don't — deeper knowledge of the person behind the search that justifies these bids.

Maybe they do.

But if those signals were working, you'd expect the expensive clicks to convert at a rate that makes the higher CPC worthwhile. They don't.

Whatever Google knows, it doesn't appear to be showing up in the results.

So should you use it?

If you're managing your own account and manual bidding isn't something you're confident with, smart bidding is probably your only realistic option. But you need to be doing two things without fail: working your negative keyword list constantly, and being very careful with match types.

Smart bidding paired with broad match is the most expensive combination in Google Ads. Broad match decides which searches trigger your ads. Smart bidding decides what you pay for them. You've handed both levers to Google. That's how a £35k/month account ends up paying £77 a click for someone who hasn't even decided what kind of driveway they want yet.

If you're working with an agency, ask them directly: manual CPC or smart bidding? If the answer is smart bidding, ask to see the search term report. The Yorkshire installer wasn't a small account having teething problems. It was spending £35k a month. Someone was just letting Google drive.