The Rental Price of Capital: How Interest Rates Decide What Gets Built

A logistics company is weighing a new distribution center. The building, racking, and automation will run $10 million up front and is expected to produce about $1.4 million a year in added profit for a decade. Good idea or bad? The honest answer is: it depends entirely on the interest rate. At 4 percent, the project is clearly worth building. At 9 percent, it quietly destroys value. The asset is identical in both worlds. What changed is the price of the capital it ties up.

That price is the interest rate, and the way to understand it is not as a number on a loan statement but as the rent on capital, the going rate for using a dollar for one year.

The interest rate as a rental price

When a firm sinks $10 million into a building, that money is no longer available to do anything else. It could have been lent out, returned to shareholders, or put into a different project entirely. The interest rate measures what those funds could earn in the next-best use: their opportunity cost. Economists at the Library of Economics and Liberty put it plainly: the interest rate is the rental price of money.¹

This is why the interest rate functions as a hurdle. If a firm can earn 7 percent risk-adjusted by leaving its capital deployed normally, then a new project has to return more than 7 percent or the firm is tying up its money in something that earns less than the going rate. The real-world anchor for that hurdle is easy to find: the cost of borrowing for a creditworthy company tracks investment-grade corporate bond yields, the Moody's Aaa and Baa series published continuously by the Federal Reserve.² The 10-year Treasury yield sits underneath nearly every other rate as the risk-free baseline.³

The idea in plain words: discounting

The tool firms use to turn "it depends on the rate" into an actual answer is net present value, or NPV. The idea behind it is simpler than the label.

A dollar received next year is worth less than a dollar in hand today, because today's dollar could be invested and grow. If the relevant rate is 8 percent, a dollar one year out is worth about 93 cents now: you would only need to set aside 93 cents today to have a dollar in a year. To value a stream of future cash flows, you discount each payment back to today using the interest rate, then add them up. Compare that total against the up-front cost. If the discounted value exceeds the cost, the project has positive NPV and is worth doing. If not, walk away.

The rate you discount with matters. It should be the firm's cost of capital: the blended cost of the money funding the project, weighing the interest it pays lenders against the return its shareholders require. That blended figure is the project's true hurdle, and it is not a number you choose freely.

You can run these calculations with a simple tool to see how the math moves: try the ROI calculator.

Walk through the numbers

Take the distribution center above. The setup is $10 million today in exchange for $1.4 million a year over ten years. Here is what NPV looks like at three different costs of capital.

At a 4 percent cost of capital, the future profit stream is worth $11.36 million in today's terms, comfortably above the $10 million price tag, so the project adds roughly $1.36 million of value. Build it.

At 7 percent, that same cash flow stream is worth only $9.83 million today, just short of the cost. NPV turns slightly negative: a coin flip that leans toward no. At 9 percent, the future cash is worth $8.98 million against a $10 million outlay, a loss of more than $1 million. Kill it.

Notice what did the killing. The cash flows never changed. The building is the same. Higher rates simply made the distant dollars worth less today and raised the bar the project had to clear. Somewhere between 4 and 7 percent lies this project's internal rate of return, the discount rate at which NPV hits exactly zero. That is the break-even hurdle. Above it, don't build. Below it, build.

When the Fed moves, the hurdle moves with it

This is not an abstraction. It is the exact mechanism through which monetary policy reaches the real economy. The Federal Reserve sets a target for the federal funds rate, the overnight rate banks charge each other.⁴ That rate ripples outward into the full structure of borrowing costs the Fed publishes in its H.15 release,⁵ and from there into corporate bond yields and the cost of capital firms actually face. The Fed adjusts this rate through open market operations, buying and selling Treasury securities to push short-term rates toward its target.⁶

Let's shift to what this looked like in practice. When the Fed raised rates sharply in 2022 and 2023, the cost of capital for businesses jumped alongside it. Projects that had penciled out at a 4 percent hurdle suddenly had to clear 7 or 8 percent, and a wave of them flipped from positive to negative NPV. Firms shelved or delayed them. The same pressure hit the housing market, where the 30-year mortgage rate climbed in direct response.⁷ That deliberate cooling of business investment and home construction is precisely how higher rates slow an overheating economy. The aggregate result shows up in the national accounts as a decline in private domestic investment, though the mechanism that drives it is just the distribution-center math applied across millions of decisions at once.

What this means for your decisions

The NPV-versus-hurdle logic is not reserved for corporate finance departments. The same discipline applies to a landlord deciding whether to add a rental unit, a self-employed person weighing a $15,000 piece of equipment, or anyone choosing between paying down a loan and investing. In every case the question is the same: does the expected return beat the rate I would otherwise earn or pay on that money?

Overall, the most durable habit the framework builds is recognizing that the answer is conditional on rates. The same investment is a yes in a 4 percent world and a no in an 8 percent world, and nothing about the investment has to change for that flip to occur. When you hear that higher interest rates are slowing the economy, you are now looking at the machinery underneath: millions of projects, large and small, quietly failing to clear a hurdle that just got higher. Run your own numbers against the real rate you face, not the rate you wish existed, and you will make the call the same way a disciplined firm does.