Leasing One Cell Tower to Three Rival Carriers
A cell tower REIT owns the structure and leases space on it to multiple carriers. Adding a second and third tenant to the same tower costs almost nothing and is almost all profit.
Owning the Structure, Not the Network
A cell tower REIT does not run a mobile network. It owns the physical towers and leases space on them to the companies that do, the wireless carriers, which mount their antennas and equipment on a structure someone else built and maintains.
This separation is the whole business. The carriers need to place equipment across wide areas to provide coverage, and building and maintaining towers themselves is capital intensive and outside their core competence. Owning towers and leasing them to carriers is a distinct and highly profitable business.
The tower is built once. Every tenant added to it afterward pays rent against an asset that already exists, which is why the second tenant is worth far more than the first.
The Economics of a Second Tenant
The defining feature of the model is what happens when a tower goes from one tenant to two or three. The cost of the tower, the land lease, the maintenance and the structure, is largely fixed. Adding a second carrier antenna to a tower that is already standing costs very little.
| Tenants on tower | Revenue | Incremental cost | Margin |
|---|---|---|---|
| One | Base rent | Full cost of tower | Modest |
| Two | Double | Minimal | Much higher |
| Three | Triple | Minimal | Very high |
Because the second and third tenants add revenue with almost no additional cost, the profitability of a tower rises dramatically with the number of tenants on it. The industry describes this as the tenancy ratio, and improving it is the single most important driver of returns. A tower with three tenants is enormously more profitable than the same tower with one.
Why the Leases Are So Good
Tower leases are long, often with terms of many years, and they typically include automatic annual rent increases known as escalators. This gives the REIT a long stream of contracted, growing revenue from tenants that are among the largest and most creditworthy companies in the economy.
The tenants also have strong reasons not to leave. Moving equipment to a different tower is expensive, disruptive to network coverage, and requires finding an alternative location, which may not exist where coverage is needed. This switching friction makes the revenue unusually sticky.
The combination, long leases, built in increases, high margins on additional tenants, and reluctant tenants, produces one of the more attractive structures in real estate.
The Growth Drivers
The demand for tower space has grown with each generation of wireless technology. More data usage requires more equipment on towers and, in some cases, denser networks with more sites. As carriers upgrade their networks, they add equipment to existing towers, which raises the tenancy ratio, and lease additional sites.
This has given the sector a long tailwind, since each network upgrade cycle drives new leasing on the existing tower base without the REIT having to build anything.
The Risks
The model has genuine vulnerabilities. Carrier consolidation is the main one: when two carriers merge, the combined company may have equipment on two nearby towers and remove one, reducing the tenancy ratio. A wave of consolidation among a small number of large tenants can meaningfully affect a tower REIT.
Technological change is the longer term question. Alternatives to traditional towers, including small cells placed on street furniture and, potentially, satellite based coverage, could over time reduce dependence on the tall tower. The industry has adapted by investing in these alternatives, but the tall tower centrality is not guaranteed forever.
Tenant concentration is the structural weakness. With few carriers, the loss or reduction of a single tenant matters, and the REIT negotiates against counterparties large enough to have real bargaining power.
The Bottom Line
A cell tower REIT owns structures and leases them to the carriers that run the networks, and its economics turn on the tenancy ratio, because each additional tenant on an existing tower is almost pure profit. Long escalating leases with sticky, creditworthy tenants make the revenue durable, and successive network upgrades have driven steady demand for more equipment on the existing base. The principal risks are carrier consolidation reducing tenancy and, over the long run, technologies that could reduce reliance on the tall tower.