When HVAC and plumbing share one ad budget, the season decides which trade gets the money
Nobody decides to stop selling plumbing in July. One budget decides it for you, and two settings can join the trades again after you split them.
TL;DR
- Give HVAC and plumbing a campaign each, with its own budget. In one campaign they draw on one daily budget, and under Maximize conversions or Target CPA the bidding spends it where it expects the most conversions. In the accounts we run, in cooling season that means air conditioning, and plumbing gets what is left. Google sets budgets per campaign, so separate campaigns are how you decide the split yourself.
- Two settings join split trades again. A shared budget puts them back in one pot, which Google says lets money "freely distribute between campaigns". A portfolio bid strategy leaves the budgets apart but gives them one target, where campaigns are "optimized collectively for a single target".
- Local Services Ads does the same on migration day: separate targets per trade in one campaign become one target. Google's alternative is a campaign per trade.
- Splitting costs the main trade spend in its busiest months, so set the split on purpose and check it before each season.
Where does the money go when two trades share one campaign?
Google's help page on budgets starts here: "Your average daily budget is the average amount that you set for each ad campaign on a per-day basis." Every ad group and keyword in that campaign draws on the same number, HVAC and plumbing alike. Google adds that it will "optimize your campaign spend for days of the month when you're more likely to get clicks and conversions", so some days run under the budget and some over it. For most campaigns the ceiling is twice the daily figure on a single day and 30.4 times it over a month; sizing that figure from trucks and tickets is its own question.
Within the day, the bid strategy decides which searches get the money. Maximize conversions sets bids "to help get the most conversions for your campaign while spending your budget", and Google says it "will try to fully spend your average daily budget". Target CPA works to an average: "Some conversions may cost more than your target and some may cost less, but altogether, Google Ads will try to keep your cost per conversion equal to the target CPA you set." Both count conversions. A water heater call and a no-cool call are one conversion each.
What follows is our reading, not a statement from Google. In a Dallas July, cooling searches are more numerous and more urgent, and they turn into calls faster. A campaign told to get the most conversions from one budget moves money toward them all day. A plumbing keyword doesn't lose because anybody judged plumbing less important. The budget runs out before plumbing's searches get their share, and a report that shows the campaign total shows nothing wrong. Under Target CPA the same thing happens through the average: the trade whose calls cost more than the single target gets bid down. Which trade loses changes with the weather.
Can HVAC and plumbing have their own budgets inside one campaign?
Not as a budget. Google's page on shared budgets gives two options: "you can assign an average daily budget to each individual campaign, or use shared budgets to allocate budget across multiple campaigns." Neither that page nor the one on daily budgets describes a budget for an ad group.
Target CPA does allow a separate target per ad group, but Google's own page says "you can set individual targets for each ad group but this isn't recommended as it can restrict Smart Bidding." The ad groups would still spend from the campaign's one budget.
The way to set the split yourself is one campaign per trade, each with its own average daily budget.
Two settings that rejoin the trades
An account can split its trades into separate campaigns and then join them again in the Shared library.
A shared budget. Google defines it as "a single average daily budget that's shared by multiple campaigns in an account", and sells it this way: "Instead of setting individual budgets, allow your overall marketing budget to freely distribute between campaigns." Google's example moves money a quiet campaign didn't spend over to a busy one, automatically. For two campaigns selling the same trade, that can be what you want. For HVAC and plumbing, our reading is that it rebuilds the single budget you just took apart: on a hot day, the quieter trade's money flows to the busier one. To check, click the Tools icon, then Budgets and bidding, then Shared budgets.
A portfolio bid strategy. Google's Target CPA page: "With a portfolio strategy, your campaigns, ad groups, and keywords are optimized collectively for a single target." Two trade campaigns under one portfolio target have one target again. Google calls it best practice to pair shared budgets with portfolio bidding, and says portfolio bidding is efficient "on campaigns that share the same goals". Our reading is that two trades with different tickets and different seasons don't share a goal in the sense that matters here. Portfolio strategies are listed under Bid strategies in the Shared library.
Local Services Ads does it for you on migration day
Google is moving Local Services Ads into Google Ads, and its help page for the move says what happens to per-trade targets:
"If you previously managed different Target CPA amounts for separate verticals under a single campaign, a unified campaign-level Target CPA will be calculated and applied to all vertical categories."
The same page gives the alternative: "setting up separate campaigns for each vertical (for example, creating separate campaigns for plumbing and HVAC in Local Services)." New campaigns are still created at g.co/localservices, not inside Google Ads. The dates, the 14-day warning email and what else changes are in Google LSA is moving to Google Ads.
What splitting did in an account we run
Rescue Air has heated and cooled houses in Dallas since 2014. Plumbing arrived in November 2021 by merger with Texas Green Plumbing, and the company name still says air. Plumbing was advertised as a line item inside the heating and cooling campaigns, sharing their budget through Dallas summers. The search terms showed the result: people who searched the brand wanted air conditioning, and people who searched for plumbing found somebody else.
The work went in this order. Calls were tied through to the CRM, so a plumbing call could be followed to a plumbing invoice. Plumbing was lifted into its own campaigns with its own budget. It got a landing page that doesn't open with an air conditioner (how plumbing is run as its own trade, reported by sold job). The existing customer list was mailed about plumbing and excluded from paid search. Then Local Services Ads opened on the plumbing categories. The split was reversed for four days in July, when heating and cooling ran short, and put back.
Rescue Air Heating, Cooling & Plumbing, Dallas–Fort Worth. With its own campaigns and budget: Plumbing share of paid spend: +18 points. Window: Two quarters against the two before. Source: Google Ads.
Limit: We reduced heating and cooling spend during a Texas summer. We can show what plumbing gained. We cannot show what air conditioning would have earned with the money back.
Same account. Plumbing jobs sold from search: 2.0 to 2.2×. Window: Two quarters against the two before. Source: Client CRM.
Limit: Two quarters is not enough to see a full water-heater cycle, which is the trade's slowest and highest-ticket work.
Same account. Cost per sold plumbing job: −24%. Window: Two quarters against the two before. Source: Call tracking.
Limit: Cost per sold plumbing job came down partly because Local Services Ads entered the mix, and that channel prices differently from search. The comparison is honest at the account level and unfair at the channel level.
Plumbing started from a small base, so our reading is that the first dollars moved across were worth more than the last dollars taken from cooling.
Two things the case taught
- Check what your name promises. If the company name carries one trade, our reading is that brand searches bring mostly that trade; at Rescue Air they did. The second trade has to be bought on its own search terms and told to your existing customers.
- Give the second trade its own landing page. A plumbing page that opens with an air conditioner can rank for plumbing and still convert badly, and the ranking stops anyone looking.
What this doesn't cover
- Standard Performance Max campaigns. How a single Performance Max budget divides between trades is a separate question, and this piece doesn't answer it.
- How much came from the customer list. At Rescue Air, the customer-list mailing and the budget split shipped five weeks apart in the same account, and we did not hold one back. Some of the plumbing gain belongs to people who already knew the company.
- Where splitting stops paying. Our reading is that moving money from the main trade pays while the second trade is small. We have not measured where that ends.
Do this in your account
- Pull spend by trade for your busiest month and your quietest month. If both trades sit in one campaign, use the ad group view. Compare the second trade's share between the two months.
- Find where the second trade lives: its own campaign with its own budget, or ad groups inside the HVAC campaign.
- Open Shared budgets (Tools icon, then Budgets and bidding). If both trades' campaigns sit on one shared budget, give each campaign its own.
- Open Bid strategies in the Shared library. If one portfolio strategy covers both trades, give each trade its own.
- Pull sold jobs by trade from your CRM for the same two months and work out cost per sold job for each trade, not cost per lead (why the two disagree).
- If you run Local Services Ads with a different target per trade, set up a separate campaign per trade at g.co/localservices. Our reading is that doing it before your migration date keeps the per-trade targets from being merged on the day; Google's page doesn't give a deadline.
- Write next month's budget per trade from its cost per sold job and the jobs its crew can take, with one line on why. Redo it before each season: in the accounts we run, the share that is right in July is not the share that is right in November.
FAQ
Should HVAC and plumbing be separate Google Ads campaigns? Yes, if you want to decide how the money splits. Google sets budgets per campaign, so separate campaigns are the way to give each trade its own budget. Keep them off a shared budget and a shared portfolio target, or the budgets are pooled again (shared budget) or held to one target (portfolio).
Can I set a budget for each ad group? Google's budget pages describe budgets per campaign or shared across campaigns, and no ad group budget. You can set a Target CPA per ad group, but Google says it isn't recommended, and the ad groups still spend from one campaign budget.
Is a shared budget ever the right choice? It can be, for two campaigns selling the same trade. Google calls it best practice to pair shared budgets with portfolio bidding, and says portfolio bidding is efficient "on campaigns that share the same goals". Across two trades with different tickets and seasons, our reading is that it undoes the split.
How much of the budget should plumbing get? There is no fixed share. Start from each trade's cost per sold job and how many jobs its crew can take, and revisit before each season. The Rescue Air change above was a result, not a target.
Does this apply to Google Local Services Ads? Yes, from migration. Different targets per trade in one campaign become one campaign-level target, and Google's alternative is a separate campaign per trade, created at g.co/localservices.
What about electrical as a third trade? Our reading is that the mechanism is the same: every trade in one budget draws on it, and the trade that converts slowest that month loses.
Sources
All read in full on September 24, 2026. Every quotation above is from these pages.
- Google Ads Help, "About average daily budgets", https://support.google.com/google-ads/answer/6385083
- Google Ads Help, "Manage a shared budget across campaigns", https://support.google.com/google-ads/answer/2517512
- Google Ads Help, "About shared budgets", https://support.google.com/google-ads/answer/10487241
- Google Ads Help, "About Maximize conversions bidding", https://support.google.com/google-ads/answer/7381968
- Google Ads Help, "About Target CPA bidding", https://support.google.com/google-ads/answer/6268632
- Google Ads Help, "Local Services Ads transition to Performance Max campaigns with pay-per-lead goals", https://support.google.com/google-ads/answer/17213585