Net Effective Rent in Commercial Leases: Full Cost Calculation
When a broker presents two lease options side by side, the number they lead with is usually the face rate. Sometimes they show net effective rent. What they rarely show is total occupancy cost, which is the only number that lets you actually compare what you will pay over the life of each lease.
Net effective rent is a useful starting point. It is not the finish line.
What net effective rent is
Net effective rent is the average annualized rent cost after accounting for all landlord concessions, spread across the full lease term. Concessions typically include free-rent periods (also called rent abatement), tenant improvement allowances, moving allowances, and any other cash contributions from the landlord.
The logic is straightforward: if a landlord charges $30 per square foot but gives you 3 months free, you are not actually paying $30. You are paying the equivalent of $30 across 9 months, then spreading that real cost across 12 months to get an annual figure you can compare against other options.
NER adjusts for the fact that lease proposals bundle concessions and face rates in different configurations to make the economics look attractive. Two leases with very different face rates and concession packages can have the same net effective rent. Comparing face rates alone would give you a false picture of which deal is better.
The formula and a worked example
Net effective rent = (total rent payments - total landlord concessions) / lease term in months
This gives you a monthly NER figure. Multiply by 12 to annualize, then divide by square footage to get NER per square foot per year.
Worked example:
- Face rent: $25.00 per square foot per year
- Lease term: 10 years (120 months)
- Free-rent period: 3 months in year 1
- Tenant improvement allowance: $50 per square foot (tenant space = 5,000 SF, so total TI = $250,000)
- No rent escalations for simplicity (real leases have annual bumps; the NER formula should incorporate them)
Total rent payments over 10 years: 120 months at $25/SF/year = $25 × 5,000 SF × 10 years = $1,250,000
Less: 3 months of free rent at $25/SF/year = $25 × 5,000 SF × (3/12) = $31,250
Less: TI allowance = $250,000
Adjusted total: $1,250,000 - $31,250 - $250,000 = $968,750
Monthly NER: $968,750 / 120 months = $8,073/month
Annual NER: $8,073 × 12 = $96,875
NER per SF per year: $96,875 / 5,000 SF = $19.38 per SF per year
The face rate was $25.00. The net effective rent, after TI and free rent, is $19.38. That is the number to carry into a comparison with other options.
Before comparing leases on NER, verify market-rate CAM using the CAM costs benchmarks for your property type.
The critical mistake: comparing leases on NER without adding NNN costs
NER captures what you pay to the landlord in base rent, net of concessions. It does not include what you pay for the building.
In a NNN (triple net) or modified gross lease, the base rent is only part of your occupancy cost. You also pay:
- CAM charges: maintenance of common areas, property management fees, landscaping, snow removal, parking lot upkeep, building security
- Real estate taxes: your pro-rata share of property taxes
- Insurance: your pro-rata share of the landlord's property and liability insurance
In a retail or industrial NNN lease, these three categories often add $8 to $20 per square foot per year on top of base rent, depending on property type, age, market, and lease language. In some markets, NNN costs on older retail properties exceed $15 per square foot per year.
Total occupancy cost per square foot = NER per SF + estimated NNN costs per SF
If Option A has an NER of $22/SF and estimated NNN of $14/SF, total occupancy cost is $36/SF. If Option B has an NER of $24/SF and estimated NNN of $9/SF, total occupancy cost is $33/SF. Option B is cheaper despite the higher face rent and lower concessions.
This comparison gets missed constantly. Brokers present NER because it is the number where their deal looks most competitive. Total occupancy cost is the number that determines your actual cost.
Why CAM estimates in lease proposals are misleading
When a landlord's broker includes an NNN cost estimate in a lease proposal, they typically use current-year or prior-year actuals for the property. Year-1 NNN estimates are real. What is not shown is the trajectory.
CAM costs escalate. Operating expenses in commercial properties typically increase 3 to 6 percent per year. A property with $10/SF NNN in year 1 may have $14/SF in year 5 and $17/SF in year 8 if there are no caps or if the caps are set generously. The lease proposal does not show you a projected year-5 or year-8 NNN cost. It shows you one number, often year-1, and lets you extrapolate.
CAM caps, if they exist, limit annual increases in controllable operating expenses. But caps often exclude taxes, insurance, and utility costs from the capped basket, which are frequently the fastest-growing expense categories. A 5% cap on controllable expenses provides meaningful protection on management fees and janitorial costs. It provides no protection on a 12% property tax increase or a 15% jump in property insurance premiums.
When building a total occupancy cost comparison across multiple lease options, apply a consistent escalation assumption to NNN costs in all options. Using year-1 estimates without escalating understates the multi-year cost difference between a lease with favorable CAM caps and one without.
What a CAM overcharge does to NER math
When you calculate NER for a lease, you are working from the lease's face rent and concessions. But CAM overcharges add costs that are not visible at signing.
After testing reconciliation samples from published audit cases through CAMAudit, CAM overcharges of 10 to 20 percent are not unusual on 5-to-10 year leases, particularly in years 4 through 7 when the landlord's reconciliation methodology has drifted from the lease language and no one has audited it.
What a 17 percent CAM overcharge does to NER math: take a lease where NER was $19.38/SF and NNN was estimated at $11/SF, giving a projected total occupancy cost of $30.38/SF. If NNN runs at $11/SF + 17% = $12.87/SF, your actual total occupancy cost is $32.25/SF. That is a 6.2 percent increase in total occupancy cost from CAM overcharges alone.
Compounded over a 10-year lease, the dollar impact is substantial. On 5,000 SF, the difference between $11/SF and $12.87/SF NNN is $9,350 per year, or $93,500 over the lease term. The lease looked cheaper on NER. It was not.
This is why tenants who chose a lease based on favorable NER without scrutinizing NNN provisions often carry the largest CAM overcharges in years 3 through 7. The decision was made on base rent economics, the lease language around CAM exclusions, caps, and audit rights received less attention, and the financial exposure accumulated over time.
How to build a real comparison across lease options
When comparing two or more lease proposals, build a multi-year cost model for each.
Step 1: Calculate NER for each option using the formula above, incorporating all rent escalations, free-rent periods, and landlord concessions.
Step 2: Add NNN costs. Use landlord-provided year-1 actuals as a starting point, then apply a consistent escalation rate (3 to 5 percent per year is reasonable as a baseline). Note whether each lease has CAM caps and what is included or excluded from the cap basket.
Step 3: Calculate total occupancy cost per year for each option over the full lease term. Sum to a total lease cost and divide by total square feet over the term to get a single comparable figure.
Step 4: Review the CAM and operating expense definitions in each lease. Leases with tighter exclusions (landlord overhead, capital excluded from CAM, management fee capped at a market rate) will have lower NNN cost trajectories than leases with broad pass-through language. This is not visible in the NER number but it is visible in the lease text.
Step 5: Check the audit rights provision in each lease. A lease with a 12-month audit window after receiving a reconciliation gives you less time to catch errors than one with a 24-month window. Leases that prohibit contingency-fee auditors limit your practical ability to enforce your rights.
The combination of these factors, not just the face rent or the NER, determines which lease is actually cheaper over its full term.
NER in practice: what the number tells you and what it does not
NER answers one question accurately: given the concessions, what is the average annual cost of the base rent you are paying?
It does not tell you about NNN trajectory. It does not capture the quality of the CAM language. It does not reveal whether the landlord has a history of aggressive reconciliations on the property. It does not reflect whether the tenant improvement allowance is adequate to build the space you actually need, or whether you will need to fund a gap out of pocket.
The tenants who end up with the largest total cost surprises are usually the ones who optimized for NER and treated NNN as an afterthought. The tenants who maintain the lowest total occupancy cost over time are usually the ones who combined reasonable NER with tight CAM language and consistent reconciliation oversight.
NER is the entry point for comparing commercial lease offers. Total occupancy cost, built on a realistic NNN trajectory and backed by strong lease language, is the number that determines whether the deal you signed stays within the range you expected.
Frequently Asked Questions
What is net effective rent?
Net effective rent is the average annualized base rent cost after all landlord concessions (free-rent periods, tenant improvement allowances, moving allowances) are deducted and the result is spread across the full lease term. It allows you to compare lease proposals with different face rates and concession structures on an apples-to-apples basis.
How do you calculate net effective rent?
Subtract total landlord concessions from total rent payments over the lease term, then divide by the lease term in months to get monthly NER. Annualize by multiplying by 12 and divide by square footage to get NER per square foot per year. For a 10-year lease at $25/SF with 3 months free rent and a $50/SF TI allowance on 5,000 SF, NER works out to approximately $19.38 per square foot per year.
Does net effective rent include CAM charges?
No. Net effective rent covers only the base rent component, adjusted for concessions. In a NNN or modified gross lease, CAM charges, real estate taxes, and insurance are paid separately on top of base rent. Total occupancy cost equals NER plus estimated NNN costs per square foot. Comparing leases on NER alone without adding NNN costs can make a more expensive lease look cheaper.
How do I compare two leases using net effective rent?
Calculate NER for each option, then add projected NNN costs for each year of the lease using a consistent escalation assumption (3 to 5 percent per year is a reasonable baseline). Note whether each lease has CAM caps and what expenses are excluded from the cap basket. Sum total occupancy costs over the full lease term to get a comparable figure. The lease with better CAM exclusions and tighter language will likely outperform on total cost even if its NER is slightly higher.