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HVAC Slow-Season Cash Reserve Calculator

Rent, insurance, truck payments, and the office still get paid in the slow months, even when the phone is quiet. Put in what a slow month costs you and what it brings in to see how much you come up short each month, the cash you need saved to get through the whole slow season, how many months your cash on hand lasts, and how much to put away each busy month to build that cushion.

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Example numbers — replace with yours. The starting values are placeholders so the form isn't empty. They are not industry averages, typical costs, or benchmarks.

What a slow month costs

What a slow month brings in

Your cash

Results

Costs each slow month (overhead + field payroll) —
Gross profit each slow month (after parts) —
Monthly shortfall —
Total reserve needed for the slow season —
Months your current cash covers the shortfall —
Still to save beyond the cash you have —
Set aside each busy month —

These are planning estimates, not a forecast. The answer is only as good as the numbers you put in — pull slow-month revenue and costs from your own bank statements or profit and loss report.

The math

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How it works

  • Costs each slow month = fixed overhead + field payroll you keep on.
  • Gross profit each slow month = slow-month revenue × gross margin %. This is what's left after parts and materials to pay the bills.
  • Monthly shortfall = costs − gross profit. If gross profit is as big or bigger than costs, there is no shortfall and you don't need a slow-season reserve.
  • Total reserve needed = monthly shortfall × number of slow months.
  • Runway = cash on hand ÷ monthly shortfall. This is how many slow months you can get through before the bank account hits $0.
  • Still to save = total reserve − cash on hand (never below $0).
  • Set aside each busy month = still to save ÷ busy months left.

Worked example

With the example numbers above: $15,000 overhead + $12,000 field payroll = $27,000 in costs each slow month. Slow months bring in $20,000 at a 50% margin, or $10,000 in gross profit. That leaves a $17,000 shortfall every slow month.

Over 4 slow months, you need $68,000 saved to get through. The $40,000 on hand covers $40,000 ÷ $17,000 = 2.4 months — not the full season. The missing $28,000 spread over 8 busy months is $3,500 to set aside each busy month.

Change slow-month revenue to $54,000 with everything else the same and gross profit is $27,000 — exactly what the month costs. There's no shortfall, so there's nothing to save for the slow season.

Ways to shrink the shortfall

  • Sell maintenance plans. Plan visits give you work to schedule in the slow months. The HVAC maintenance agreement calculator shows what a plan brings in.
  • Price for the whole year. If your hourly rate only works in busy months, the slow months will always come up short. The HVAC break-even hourly rate calculator spreads a full year of overhead over your billable hours.
  • Set a revenue target for the year. The HVAC revenue goal calculator turns it into jobs and calls per day, so you know what busy months have to bring in.
  • Move the cash into its own account. Money you set aside in a separate savings account is harder to spend on something else during the busy season.

Things this leaves out

  • Timing. The math treats every slow month the same. If one month is much worse than the rest, plan around that month.
  • Money you owe or are owed. Unpaid customer invoices, supplier bills, loan payments, and tax payments can move your cash up or down. Add big ones to overhead or take them out of cash on hand. The HVAC A/R and DSO calculator shows how much cash is tied up in unpaid invoices.
  • A line of credit. Borrowing can bridge a gap, but it costs interest and has to be paid back in the busy months.

We don't quote typical overhead, slow-season length, or margins here because they vary widely by market and shop. That's what the anonymous Owner Numbers survey collects, so owners can compare against real peers.

Where to get your numbers

The guide The HVAC KPIs Every Shop Owner Should Track (2026) shows how to track gross margin and net profit month by month, which is where your slow-month numbers come from.

Related tools

Need to know what an hour of work really costs? The HVAC break-even hourly rate calculator works it out from your overhead and wages. Want to know what the busy months have to bring in? The HVAC revenue goal calculator turns a yearly target into jobs and calls per day. Still planning to open your own shop? The HVAC startup cost & first-year cash calculator shows how much cash you need to get through the first year.