What is the cost of capital and why does it matter?

The short answer

Imagine a coffee chain considering whether to open ten new locations. The capital required must come from somewhere — bank debt, retained earnings, or equity issuance. Each source has a price. The blended cost of all sources is what corporate finance calls the cost of capital.

This number is not academic. It defines the hurdle rate below which projects destroy shareholder value. A factory expansion expected to return 7% destroys value if the company’s WACC is 9%. The same expansion creates value if the WACC is 5%.

The decisive nuance is that the cost of capital is not constant. It moves with risk-free rates, credit spreads, equity risk premia, and the company’s leverage. When monetary regimes change, the entire investment landscape shifts — even if the underlying projects do not.

→ New to corporate finance basics? Investment vehicles and real returns

What the data shows

The U.S. cost-of-capital reset since 2021 (Damodaran data, FRED, Bain analysis):

• Risk-free rate (10-year Treasury): from 1.5% in late 2021 to a peak above 5% in October 2023
• Investment-grade BBB corporate bond yields: from roughly 2.3% in late 2021 to peaks near 6.5% in 2023
• U.S. large-corporate LBO debt yields (proxy for high-yield financing): from roughly 6% in 2015 to 8-9% by 2025 according to Bain
• Damodaran’s January 2026 sector WACC dataset shows median U.S. industry WACC clustering between 8% and 11%, versus 5%-7% range typical of 2019-2021
• Equity risk premium (Damodaran implied ERP) has hovered around 4-5% across the period — meaning the WACC rise was driven primarily by the risk-free leg

The exception worth noting: highly cash-flow-positive technology firms with no net debt (Apple, Alphabet) saw their WACC rise less than the average — their financing is dominated by equity, and equity cost rose less in proportion than debt cost.

→ Dataset: U.S. Investment Grade Credit Spread

Why it happens — the macro mechanism

The cost of capital is built from independent components, each driven by different macro forces.

Channel 1 — The risk-free anchor. Cost of equity = risk-free rate + beta × equity risk premium. Cost of debt = risk-free rate + credit spread × (1 − tax rate). Both legs share the same anchor: the Treasury yield curve. When the Fed lifts policy rates and the long end repriced, every WACC in the economy moves with it. This is why bond prices fall when yields rise — and the same arithmetic flows through to equity discount rates.

Channel 2 — The neglected leverage channel — angle worth highlighting. Standard textbooks present WACC as a weighted average where the weights are debt-to-value and equity-to-value. But these weights are themselves rate-dependent: when rates rise, equity values fall (higher discount rates), debt values fall less (collateral and seniority), so the leverage ratio mechanically rises and the WACC formula amplifies the rise. The pre-2022 ZIRP era hid this dynamic because rate moves were small and equity multiples were stable.

Channel 3 — The Modigliani-Miller corner case. Under the original Modigliani-Miller theorem (1958), capital structure is irrelevant to firm value in a frictionless world. With taxes, bankruptcy costs, and information asymmetries, capital structure matters — and the optimal mix shifts when relative costs of debt and equity change. Companies that took on aggressive leverage at near-zero rates in 2020-2021 face a structural WACC reset as those debts come up for refinancing.

Synthesis by regime: in the post-2008 ZIRP regime (2009-2019), aggregate WACC drifted to historical lows around 6%, encouraging long-duration projects and asset-heavy expansion; in the 2020-2021 stimulus phase, near-zero short rates pushed WACC even lower temporarily; in the post-2022 normalization (2022-2025), WACC rapidly reset toward 9-11%, invalidating projects approved at the prior hurdle rate. The 1979-1982 Volcker tightening offers the most extreme historical analog — corporate WACCs above 14% sterilized capital expenditure for years.

The cost of capital is the price tag on the future — when that price changes, the entire opportunity set is repriced overnight.

→ Analytical framework: Equity valuation: real rates, multiples, earnings

What it means for different economic actors

CFOs and corporate executives face a recalibration of investment hurdle rates. Projects that cleared the bar at 7% WACC may not clear it at 10%. This drives the slowdown in capex visible across S&P 500 industrials since mid-2023.

Equity investors see WACC indirectly through valuation multiples. CAPE multiples compress when the discount rate rises, all else equal, which is why high-multiple growth equities suffered the worst drawdowns in 2022.

Bond investors see WACC directly through credit spreads — wider spreads mean a higher all-in borrowing cost for issuers, and any spread widening from current levels would amplify the WACC reset.

A common error is to treat WACC as a single corporate number. It varies by sector, by capital structure, by geography, and by the marginal funding source the firm is currently tapping.

Practical observation

Go deeper

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Frequently asked questions

Is WACC a fixed number for a company?

No — and this is one of the most common misunderstandings of corporate finance. WACC depends on the risk-free rate (which moves with monetary policy), credit spreads (which move with the credit cycle), equity risk premium (which moves with valuations and macro uncertainty), and the firm’s capital structure (which itself shifts with rate moves). Damodaran updates his sector WACC database annually precisely because the inputs change. A WACC computed in 2021 was already obsolete by mid-2022.

How does WACC differ from a hurdle rate in practice?

WACC is the theoretical floor — the minimum return needed to satisfy capital providers. The hurdle rate is what executives actually require for project approval, and it typically embeds a margin above WACC to account for execution risk, optionality value, and managerial uncertainty. Empirical surveys (Graham and Harvey) find that corporate hurdle rates often exceed computed WACC by 200-400 basis points, which means the effective cost of capital felt by project sponsors is meaningfully higher than the textbook number.

Why did the cost of equity rise less than the cost of debt in 2022-2024?

The cost of debt is contractually anchored to risk-free rates plus credit spreads — when both moved up sharply in 2022, debt costs roughly doubled in mechanical fashion. The cost of equity is anchored to risk-free rates plus an equity risk premium, but the implied ERP actually compressed during the rate-rise phase because expected earnings remained robust. The net result was that pure-equity-funded firms saw a smaller WACC reset than highly-levered firms — visible in the relative resilience of large tech versus levered industrials in 2022-2023.

Last updated — 12 July 2026