The tail is the contracted life left after the loan matures. It costs debt on day one and buys the room to restructure later: here is how to price both.
The debt tail should be long enough that, if CFADS falls and stays down, the loan can still be repaid from contracted cash before the contract ends. It is a trade: every year of tail shortens the tenor and costs debt today, and buys restructuring room tomorrow. On an illustrative project with 20.0 million of CFADS under a 20-year PPA, a 2-year tail cuts the debt from 176.5 to 166.6 million and lets the loan survive a sustained 27.4 per cent fall in CFADS; with no tail the margin is 23.1 per cent.
Worked in full in The Project Finance Handbook by Julian R. Sterling, with every figure reproduced in a free workbook.See the book on Amazon →
The tail is the period between the final maturity of the loan and the end of whatever produces the revenue: the PPA, the concession, the lease, or the reserve life of a field. A lender that sizes on contracted cash flow wants some of that contracted cash left over after the scheduled last repayment. If the project underperforms, the loan can be re-profiled into those years rather than refinanced against merchant revenue that nobody has underwritten. The tail does nothing in the base case. It is a stress-case instrument, which is why it is easy to give away in negotiation and expensive to lack.
| Input | Value |
|---|---|
| Project cost | 220.0 |
| CFADS a year under the PPA, flat | 20.0 |
| PPA term, years | 20 |
| Technical life, years | 30 |
| Merchant CFADS a year after the PPA | 14.0 |
| All-in cost of debt | 6.0% |
| Sizing DSCR | 1.30x |
| Tenor in the base case: PPA less a 2-year tail | 18 years |
Step 1: size the debt on the tenor that the tail leaves. With flat CFADS the sculpted and annuity profiles coincide.
Debt service = 20.0 / 1.30 = 15.38 a year
Debt = 15.38 × annuity factor(6.0%, 18 years) = 15.38 × 10.83 = 166.6
Excel: =PV(6%, 20-2, -20/1.3)
With no tail the tenor is the full 20 years, the factor is 11.47, and the same cash flow supports 176.5. The two years of tail cost 9.9 of debt, which equity has to fund instead.
Step 2: measure what the tail buys. Take the present value of all contracted CFADS to the end of the PPA, at the debt rate, and divide by the debt. This is a cover ratio over the contract life rather than the loan life, the contracted version of a PLCR.
PV of contracted CFADS = 20.0 × 11.47 = 229.4
PPA-life cover ratio = 229.4 / 166.6 = 1.38x, against an LLCR of 1.30x over the tenor
Sustained fall the loan can absorb = 1 − 1 / 1.38 = 27.4%
The 62.8 of headroom between 229.4 and 166.6 has two sources: 50.0 from the DSCR cushion inside the tenor, and 12.8 from the present value of the two tail years themselves.
Suppose CFADS drops from year 1 and never recovers. How long does the 166.6 loan take to repay if every dollar of CFADS goes to the lender?
| CFADS fall | CFADS a year | Years to repay | Inside the 20-year PPA? |
|---|---|---|---|
| 20% | 16.0 | 16.8 | Yes, inside the tenor |
| 25% | 15.0 | 18.8 | Yes, only because of the tail |
| 30% | 14.0 | 21.5 | No: repayment relies on merchant years |
At a 25 per cent fall the loan runs 0.8 of a year past its 18-year maturity. With a tail, that is a re-profiling into contracted cash. Without one, it is a refinancing against merchant revenue, or a default. That is the practical definition of the right tail: the length that keeps the lender's stress case inside the contract. The annual DSCR shows none of this: a 20 per cent fall takes cover to 1.04 times whatever the tail, because debt service is 15.38 in every case. What differs is whether contracted years remain to extend into.
| Tail, years | Tenor | Debt | Gearing | PPA-life cover | Sustained fall absorbed | Equity IRR |
|---|---|---|---|---|---|---|
| 0 | 20 | 176.5 | 80.2% | 1.30x | 23.1% | 11.79% |
| 1 | 19 | 171.7 | 78.0% | 1.34x | 25.2% | 11.11% |
| 2 | 18 | 166.6 | 75.7% | 1.38x | 27.4% | 10.57% |
| 3 | 17 | 161.2 | 73.3% | 1.42x | 29.7% | 10.12% |
| 4 | 16 | 155.5 | 70.7% | 1.48x | 32.2% | 9.76% |
| 5 | 15 | 149.4 | 67.9% | 1.54x | 34.9% | 9.45% |
Each year of tail costs about 5 of debt and adds two to three points of stress capacity. If the lender's stress case is a sustained 25 per cent fall, one year suffices; if it is 30 per cent, the project needs four, and the 11.1 of debt lost between a two- and a four-year tail is a lot of equity to find. Moving from no tail to two years costs the sponsor 1.22 points of pre-tax equity IRR here, the price of a loan that can be fixed without a refinancing.
Tail lengths are illustrative and vary by lender, market and asset. A long-lived asset with a credible merchant tail after the PPA, here 14.0 a year for ten years, may get a shorter contracted tail than a concession that hands the asset back at the end.
The common mistake is to treat the tail as a tenor input and stop there, reading only the debt it costs. The tail exists to be used in a stress, so it should be sized with one: decide the sustained fall the deal must survive, compute the PPA-life cover ratio that implies, and choose the shortest tail that meets it. The second mistake is to confuse the LLCR with the cover over the contract. With flat CFADS the LLCR at sizing equals the DSCR, 1.30 times, whatever the tail; the tail shows up only in the longer ratio. The difference is set out in how to calculate the LLCR.
The Project Finance Handbook sizes its data centre loan on two tests and a third for what is left at maturity, and prints the rent at which the balloon refinances; the model is in the free workbooks for the book's two cases.
It is the period between the final maturity of the loan and the end of the contract or concession that produces the revenue. If a 20-year PPA backs an 18-year loan, the tail is two years. Those two years of contracted CFADS, worth 12.8 million in present value on a 20.0 million a year illustrative project, are what a lender can extend into if the cash flow underperforms.
The tail is a length of time; the project or PPA-life cover ratio is what it buys, measured as the present value of CFADS over the remaining contract divided by the debt. On the illustrative project, 229.4 million of contracted CFADS against 166.6 million of debt gives 1.38 times, against 1.30 times for the loan life cover ratio over the 18-year tenor.
Yes, because it shortens the tenor and so the debt the same cash flow supports. On the illustrative case each year of tail removes about 5 million of debt; moving from no tail to two years cuts debt by 9.9 million and the pre-tax equity IRR by 1.22 points, from 11.79 to 10.57 per cent.
This article is one calculation from The Project Finance Handbook. The book takes the same case from first principles to the decision, chapter by chapter, and every figure it prints is a live formula in the free companion workbooks.
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