Why Most Investors Ignore Loss-to-Lease and How It's Destroying Their Rent Growth Assumptions

You're sitting in front of a deal.
The broker's comp analysis says market rent is $1,450.
Your property's current average rent is $1,200.
You're building in 3% annual rent growth.
By year five, you're projecting $1,320/month.

You just built a fantasy.

What Loss-to-Lease Actually Is

Loss-to-lease is the gap between what you're charging and what the market will pay.
$1,450 minus $1,200 = $250 in upside.
That $250 isn't yours to keep—it's earned by moving bodies, turning units, and absorbing the cost of getting there.

Most investors see that spread and treat it like found money.
They pencil it into year one or year two as if the rent roll will magically push to market overnight.
They don't ask themselves what it actually costs to capture it.

The Broker's Comps Are Not Your Operating Reality

That market-rent number the broker showed you?
It's achievable—if you have a vacant unit, a qualified tenant who signs immediately, no concessions, and zero turnover costs.

Your actual new-lease data tells a different story.
If you pull the rent roll and look at what's actually leasing in this market, you might see $1,380, not $1,450.
You might see a 30-day concession required to fill vacancy.
You might see a 15% vacancy window between move-out and new occupancy.

A single month of vacancy plus concessions and turnover costs can eat $3,000–$5,000 per unit.
That turns your $250 upside into a $50 upside—if you're lucky.

Proof Over Hope: How to Quantify Loss-to-Lease

Your rent growth projections are built on proof, not hope.
Proof means you pull the actual rent roll and look inside it—not just at the blended average.

You need two numbers: renewal rate (what existing tenants pay to stay) and new-lease rate (what new tenants actually sign for).
If your rent roll shows 40% of units renew at $1,220 and new leases sign at $1,280, your blended rent growth is closer to 1.5% than 3%.

The 3% is the broker's comps in a vacuum.
The 1.5% is what actually happens when you operate the building.

Now model the turnover: how many units lease per month, what's the lag between move-out and occupancy, what concessions are standard, what's the cost per turn.
That math tells you whether you can actually close the $250 gap—or whether it will stay a theoretical spread forever.

Loss-to-Lease as a Bet, Not a Guarantee

Here's the reframe: loss-to-lease isn't free money—it's a bet.
A bet that you can turn units consistently, a bet that the market will hold, a bet that you won't need concessions to fill the gap, a bet that occupancy won't slip while you're pushing rents.

If you're modeling rent growth without quantifying that bet, you're projecting the upside while burying the risk.
You're building a business plan that only works if everything goes right.

That's not underwriting.
That's hope with a spreadsheet.

The Discipline That Separates Confident Underwriters

The investors who get this right pull the rent roll before they build the model.
They pull it before they write the offer.

They map the lease expirations across the year, pull actual new-lease data from the last 12 months, compare it to what's already in place, and calculate the real cost of capturing the spread.
They stress-test: what if market rents dip 2% in year two, what if you need 60 days to turn instead of 30, what if concessions go from zero to 15%.

Only after that do they build the rent growth assumption.

They know whether the deal works with real rent growth or only with broker optimism.
That knowledge is worth six figures in avoided mistakes.

If you want to build the discipline to see through loss-to-lease before the deal is priced, the Free Underwriting Masterclass walks through exactly how to pull and analyze that data.
It takes 30 minutes and you'll immediately apply it to the next deal you look at.

By Jason L. Williams, Ph.D.

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