How to Build a 13-Week Cash Flow Forecast for an HVAC Company

You know the feeling. It’s Sunday night, you’re looking at the bank balance, and the question isn’t whether the month was profitable. It’s will I have cash in week 9 when payroll, the tax payment, and the truck all land?

This is the first tool I build with every new HVAC client because it answers that question fast. A 13-week cash flow forecast is a rolling weekly direct-method model that tracks cash receipts and disbursements over roughly one quarter, then gets refreshed every week with actuals and a new week 13 so you can see the exact week cash gets tight instead of finding out after the fact.

This is one piece of managing cash flow in a home service company. The full guide covers the cash floor, seasonality, and the weekly rhythm. This article is just the build. Here’s the sheet, column by column.

What You Are Building

You are building a 13-week cash map tied to the week money clears the bank.

That distinction matters. Booked sales can make a month look fine while week 9 still breaks you. This sheet separates profit talk from cash talk by lining up receipts and disbursements by bank-clearance week, not by invoice date or closed revenue.

Keep it to one sheet. Thirteen weekly columns. A small set of rows. Opening cash, money in by source, money out by type, ending cash, your cash floor, and the gap above or below it. I build these in Google Sheets or Excel because they are fast to update on Monday morning and easy to audit when a number looks off.

The point is not presentation. The point is a sheet you can update in 20 minutes and use to make a call before payroll, tax drafts, or a supplier payment hits. Near weeks should get tight fast because you already know most draft dates, payroll runs, debt payments, and large vendor checks. As those known items replace guesswork, the near term should get more accurate fast.

If you want a starting file instead of building the grid from scratch, use these cash flow forecasting template Excel resources.

Practical rule: If the sheet cannot show which specific week cash drops below your floor, it is too summarized to run the business.

Step 1: Set Up the Columns and Rows

Start with 13 columns labeled Week 1 through Week 13. Date each column with its Friday. I do that because most owners think in “this week ending Friday,” and it makes payroll and drafts easier to scan.

Then build the rows in this exact order:

• Opening cash

• Receipts

  • Service collections

  • Install deposits

  • Install progress & final payments

  • Maintenance renewals

  • Financing company payouts

  • Other

• Total receipts

• Disbursements

  • Payroll

  • Payroll tax

  • Rent

  • Truck payments

  • Insurance

  • Software

  • Debt service

  • Estimated taxes

  • Supplier & vendor

  • Owner draws

  • One-offs

• Total disbursements

• Ending cash

• Cash floor

• Above/below floor

Here’s the layout.

The only formula that really matters is this one: ending cash in week 1 becomes opening cash in week 2. Then week 2 rolls into week 3, and so on. That’s the whole engine.

A practical 13-week model is built from direct cash movements, not accounting profit, so the core lines are cash receipts and cash disbursements such as payroll schedules, AP aging, debt service dates, taxes, and recurring overhead commitments.

Keep the cash floor row visible the whole time. Several forecasting templates are built around starting cash, weekly columns, ending cash, and a minimum-cash threshold so you can see immediately when a week falls below the floor and decide whether to accelerate collections, delay payments, or draw financing.

Step 2: Opening Cash

Your opening cash is the cleared bank balance this morning.

Not the QuickBooks Online balance. Not pending deposits. Not what you think should have cleared by now. I use the cleared cash in the operating account because this forecast only works if week 1 starts with a bank number.

If you have multiple accounts, sum operating only. Leave the tax set-aside out. Leave the reserve out. Those dollars already have a job.

If you start with inflated opening cash, every week after that lies to you.

Step 3: Receipts From ServiceTitan

Most first forecasts go sideways. Owners pull booked sales, sold jobs, or board revenue and drop those numbers into the sheet. That’s not a cash forecast. It’s a wish list.

A good 13-week HVAC forecast maps inflows by the week the money clears, not the week the work was performed, because contractor cash timing is driven by AR collection lag, retainage-style delays, payroll dates, vendor due dates, and tax timing.

Service collections

Service collections are usually the easiest row.

I pull the last 4 weeks’ average from ServiceTitan and use that as my starting point. Then I adjust for the season we’re heading into. If I know I’m moving into a slower shoulder stretch, I don’t let the recent hot month fool the sheet.

This is also where clean data matters. If your field data and accounting data don’t line up, you’ll spend your Monday guessing. That’s why I care a lot about ServiceTitan and QuickBooks Online matching cleanly before I trust the forecast.

Install deposits

This row comes from the booked install schedule.

Use deposit % × sold price, and place it in the week the job is scheduled to start. Not when the comfort advisor sold it. Not when the invoice was created. The week the cash is expected to hit.

If your team sometimes takes deposits late, fix the lag in the sheet. Don’t pretend process discipline is better than it is.

Install progress and final payments

Put the remaining balance in the week the job closes.

If you’re heavy on financed work, this line gets smaller and the financing payout row gets bigger. That split matters. I’ve seen plenty of shops show a strong install month on paper while the bank stays thin because the cash landed later than the owner expected.

Forecast collections, not sales. The sale is a ServiceTitan number. The collection is a bank number.

Maintenance renewals

Pull this from the membership report and place renewals by week.

This is cash, not revenue. Don’t let the accounting treatment distract you from the timing. If the renewals bunch up in a certain stretch, that can create a helpful bump in a slow season. If they’re auto-drafted later than you assume, the sheet needs to reflect that.

Financing payouts

Use the sold amount minus dealer fee, then put it in the week the financing company funds.

Usually that’s after completion, with a lag that’s specific to how your jobs close and how your financing company settles. Use the lag you see in your bank, not the promised lag in the rep’s pitch.

AR aging

This is the row owners usually overstate.

My rule is simple:

• 0 to 30 days lands in the next 2 weeks

• 31 to 60 days lands in weeks 3 to 5

• Over 60 days stays off the sheet until it’s collected

About 80 percent of over-60 AR does eventually get collected in the shops I work with. That’s better than most owners assume. But “eventually” is the problem. You can’t date it, and a forecast is a calendar, not a probability. Leave it off, work it hard, and treat it as upside when it lands.

Seasonality matters here too. The same AR that collects in three weeks in July can take six in November, when the commercial accounts slow down with everyone else.

Step 4: Disbursements From QuickBooks

Cash problems usually start on the outflow side. Booked profit can look fine on Friday and the bank can still get pinched on Wednesday because payroll, AP, and debt all cleared in the same week.

Pull disbursements from QuickBooks by bank clearance week, not by month and not by P&L category. I want the sheet to match the week cash leaves the account. That is what makes the Monday update useful.

A good 13-week forecast includes scheduled payments, approved bills, recurring drafts, and purchase commitments that have not cleared yet. If inventory or equipment gets bought before the related install cash comes in, the forecast needs to show that timing gap.

Payroll and payroll tax

Start with payroll. It is usually the biggest draft and the least forgiving one.

Use the actual pay date. Then add payroll taxes in the week your provider pulls them. Some processors sweep the same day. Others pull a few days later. Use what cleared your bank last month, not what the setup screen says should happen.

I check this row first every Monday.

Fixed monthly drafts

Load the recurring hits next. Rent, truck notes, insurance, software, phone, fuel cards, debt service.

Put each one in the week it drafts. Do not divide a monthly bill across four weeks to make the sheet look tidy. That hides squeeze weeks, which is the whole point of the forecast.

Suppliers, equipment, and subcontractors

This row needs judgment.

QuickBooks will show open bills. It will not always tell you what is about to get bought for jobs already sold but not yet installed. Add expected equipment purchases based on the install board and vendor terms. If a condenser order will be paid next Thursday, put it in next Thursday’s week even if the customer cash will not clear for two more weeks.

Subcontractors belong here too. Crane, electrical, controls, and permit-related checks often hit before final collection.

Taxes, debt, and owner draws

Estimated taxes go in the due week for the full amount. Loan payments go in the week the bank drafts them. Owner draws need to be explicit, not buried in a catch-all row.

Use separate lines for one-offs that can knock the week sideways:

• truck down payment

• annual insurance renewal

• large software renewal

• sales tax catch-up

• settlement payment

Those are the rows that turn a forecast from an accounting exercise into a decision tool.

If you cannot pull this from QuickBooks in under an hour, fix the books first — here’s how an HVAC chart of accounts should be built. The forecast only works if the disbursement rows reflect real draft dates, real AP pressure, and real clearance timing.

Step 5: Ending Cash Versus The Floor

Wednesday looks fine on paper. Friday payroll clears, an equipment deposit hits, and the tax draft lands Monday morning. That is how an owner ends up surprised by a week that was visible three weeks earlier.

The formula stays simple. Ending cash = opening cash + receipts – disbursements.

Then stack that number against your cash floor in every week. I keep the floor on the sheet as a fixed line across all 13 columns so the problem weeks show up fast.

Your floor is the minimum bank balance that lets the company operate without scrambling. Payroll has to clear. Vendor terms have to stay intact. Cards cannot bounce. A week can stay positive and still be a bad week if it drops under that line.

Booked sales stop mattering. The floor is tested against cash that clears the bank that week, not against revenue, gross margin, or jobs marked sold. That separation is the whole point. Profit explains whether the business works. Cash timing decides whether you can make it through the month.

I use one more row here: above or below floor. If ending cash is $82,000 and the floor is $100,000, the row should show negative $18,000 in plain sight. That is the decision number. It tells you whether to press AR harder, delay a discretionary spend, stage an equipment purchase, or move an owner draw.

Set the floor with some honesty. If your margin structure already leaves little room for mistakes, your buffer needs to reflect that. My guide to HVAC business profit margins helps frame that risk, but the forecast itself should stay tied to bank clearance weeks, not accounting comfort.

Step 6: The Monday Update

The sheet works because you touch it every Monday. If you skip the rhythm, it becomes a stale spreadsheet and then a false comfort.

A 13-week cash flow forecast is designed as a rolling weekly model. Each week, the completed week drops off, a new week is added at the end, and the forecast is refreshed with actuals and updated assumptions so the horizon stays fixed at 13 weeks.

My Monday update takes about 20 minutes:

1. Replace last week’s forecast with actuals. Opening cash, what came in, what went out.

2. Delete week 1. Shift every column left.

3. Add a new week 13.

4. Re-pull AR aging and the install schedule from ServiceTitan. Update the next 4 weeks.

5. Confirm this week’s disbursements against what’s scheduled.

Then make one decision.

That last part matters. The forecast is not a reporting exercise. It’s a decision tool. Do we push a truck payment? Do we call over-30 AR? Do we hold a discretionary spend for two weeks?

The first 3 to 4 weeks should be tight. Weeks 9 to 13 are direction, not precision. That’s fine.

The point is seeing week 9 in week 1.

What It Looks Like When It Works

Here’s a worked example.

A $6M HVAC shop, 13 weeks starting the first Friday in October. Opening cash is $268,000. Cash floor is $150,000.

What’s driving it

Payroll runs biweekly, weeks 1, 3, 5, 7, 9, 11, 13, at about $81,000 including payroll tax. Rent and debt service draft in weeks 1, 6, and 10. Truck notes and insurance hit in weeks 2/3, 7, and 11. The annual insurance renewal lands in week 4. A truck down payment sits in week 6. Membership renewals bunch into week 8. Service collections sag through the October shoulder and recover as heating season starts in November.

What the owner sees

The bank never goes negative. Cash ends the quarter at $219,000, down $49,000, a normal shoulder-season drain. But week 7 runs $48,000 under the floor, and week 9 runs $19,000 under. Both are visible in week 1, six weeks before either one arrives.

Three moves, made in week 1

• Push the truck down payment from week 6 to week 11, $18,000

• Work the over-30 AR and pull $45,000 into week 7

• Hold marketing through weeks 5 to 7, $18,000

That’s $81,000 back into the weeks that needed it. Week 7 goes from $102,000 to $183,000. Week 9 clears too. None of those decisions are dramatic. That’s the point. Boring decisions, made early, because the sheet showed you the week.

“The forecast didn’t find more money. It found the week.”

Five Mistakes I See In Every First Forecast

The first version is usually wrong in predictable ways. Not because the owner is careless. Because the business has been thinking in sales and P&L, not bank timing.

Forecasting sales instead of collections

Booked work is not bank cash.

I see this most with installs. The owner drops sold revenue into the week the job was signed. Then payroll hits before the cash does, and the sheet misses the problem. Use collection timing only.

Spreading fixed costs evenly

Monthly averaging belongs in a budget, not here.

Rent, truck payments, software, and debt service need to sit in the week they draft. A weekly cash tool loses its value fast when fixed costs are smeared across four columns.

Leaving payroll tax off

This one is common.

Payroll gets entered because everyone remembers it. Payroll tax gets missed because it drafts later or through a provider. Then the owner wonders why the actual bank moved more than the forecast.

Counting the tax set-aside as operating cash

I still see this a lot.

If money is already reserved for taxes, it is not available for operations. Counting it here inflates opening cash and creates fake breathing room.

Building it once and never opening it again

This is how owners get surprised in October.

The weekly rhythm is the whole point. If you want to understand that slower stretch better, read about HVAC shoulder season.

When the owner is the only person who can update the sheet, it dies. The bookkeeper should own the Monday update. The owner should read it and decide. If nobody on your team can own that rhythm, that’s the part I take over for clients.

If you want to talk through that, schedule a call. If you’re not sure where you stand today, the cash flow scorecard will show how you’re tracking cash right now.

Questions Owners Ask

Do I need special software for a 13-week cash flow forecast

No. Use a sheet.

ServiceTitan and QuickBooks feed the file. They don’t replace it. I’d rather see a plain spreadsheet updated every Monday than a fancy tool nobody trusts.

How accurate does it need to be

Weeks 1 to 4 should be tight. Weeks 5 to 13 are more directional.

That gets better with repetition. Once your process matures, the near weeks should be close because the known items are already on the calendar.

Should the forecast use the P&L or the bank

The bank. Always.

This is a cash tool. Profit matters, but this sheet answers a different question. It tells you when money clears and when money leaves.

How long does the first build take

If the books are clean, an afternoon is realistic.

If they aren’t, it takes longer. That’s not bad news. That’s the finding. The forecast usually exposes whether your accounting and field data are usable enough to run the business week to week.

I help HVAC owners build this exactly the way I described here. That means clean numbers from ServiceTitan and QuickBooks, a weekly cash rhythm, and a forecast that tells you what week needs attention before the bank does. If you want help putting that in place, schedule a call and bring last month’s bank statements.