Multi-Building LED Retrofit: AEC Revenue Model for an Office Park

Office parks present a lighting profile that single-building models miss. Interior office lighting runs on business hours. Garage, pathway, and facade lighting runs dusk to dawn every day of the year. The two behave differently enough that averaging them produces a materially wrong answer.

This model works through both, then addresses the ownership question that determines who actually collects the revenue.

The baseline

A 500,000 square foot suburban office park across eight buildings, with structured parking and site lighting.

Interior lighting — recessed troffers and T8 fluorescent fixtures at roughly 1.1 W per square foot, operating about 3,000 hours annually on a twelve-hour weekday schedule.

500,000 sq ft × 1.1 W = 550 kW · 550 kW × 3,000 hours = 1,650,000 kWh

Exterior and garage lighting — metal halide and high-pressure sodium across structured parking, pathways, and facades, at roughly 150 kW connected load, operating dusk to dawn on photocell control at about 4,380 hours annually.

150 kW × 4,380 hours = 657,000 kWh

Total lighting consumption: 2,307,000 kWh annually.

Note the asymmetry. Exterior lighting is 21% of connected load but 28% of consumption, because it runs 46% more hours.

The retrofit

Interior — LED troffers with integrated occupancy sensing and daylight harvesting on perimeter zones. Fixture wattage reduction plus controls would reduce interior lighting consumption by approximately 60%.

1,650,000 kWh × 0.40 = 660,000 kWh

Exterior — LED area and garage fixtures with photocell and adaptive dimming, reducing output during low-occupancy overnight hours. Approximately 65% reduction.

657,000 kWh × 0.35 = 230,000 kWh

Total after retrofit: 890,000 kWh.

Savings and AEC revenue

2,307,000 − 890,000 = 1,417,000 kWh = 1,417 MWh

One AEC per MWh conserved:

Over a ten-year measure life, roughly $326,000 to $381,000.

AECs are issued from the PennAEPS certification date forward. At this scale, each month uncertified forgoes approximately $3,179 in credit revenue that is not recoverable later.

Why exterior lighting outperforms its size

Exterior represents 21% of connected load and produces 30% of total savings in this model. Three reasons:

• Operating hours. 4,380 versus 3,000 — 46% more runtime on every watt saved.
• Baseline inefficiency. Metal halide and high-pressure sodium fixtures are considerably less efficient than the fluorescent fixtures they sit alongside, so the same LED replacement yields a larger percentage reduction.
• Adaptive control headroom. A parking structure at 3 a.m. can operate at reduced output without complaint. An occupied office cannot.

Facilities that treat exterior lighting as an afterthought in retrofit scoping consistently leave the highest-yield measure on the table.

Aggregation across buildings

Eight buildings could be registered as eight separate projects or as one portfolio.

Portfolio registration is generally preferable. One application, one GATS generator account, one set of documentation, one reporting stream. Administrative overhead does not scale linearly with building count, so eight separate registrations cost considerably more effort than one for the same credit volume.

It also makes smaller buildings economic. A single 40,000 square foot building saving 110 MWh annually may not justify standalone registration. Inside a portfolio it contributes without carrying its own overhead.

Who owns the credits

This is the question that determines whether an office park owner collects anything, and it is frequently answered late.

52 Pa. Code § 75.13(i) provides that a customer-generator eligible for net metering owns the alternative energy credits of the electricity it generates, unless a contract expressly assigns ownership elsewhere. The default favors the party generating — but the contract governs.

In multi-tenant commercial real estate, several structures complicate that:

• Triple-net leases where tenants pay utilities directly. If the landlord funded the retrofit but tenants pay the electricity, who conserved the electricity is a question the lease may or may not answer.
• Common area maintenance recovery. Where retrofit cost was recovered through CAM charges, tenants have arguably funded the measure.
• Green lease provisions. Newer leases increasingly address environmental attributes explicitly. Older ones are usually silent.
• ESCO or performance contracts. May assign attributes to the contractor as part of the financing structure.

Where leases are silent, the § 75.13(i) default applies. Where they are not, they control. Read them before preparing an application.

Documentation

Where a utility rebate was claimed through PPL, PECO, or FirstEnergy, the application typically contains a third-party-reviewed savings calculation that supports certification directly.

Without a rebate: fixture-count schedules by building, before-and-after wattage specifications, operating-hour assumptions by zone, control system commissioning documentation, and pre- and post-installation utility data.

Fixture schedules matter more in multi-building portfolios than anywhere else. A count that is approximately right across eight buildings compounds into a savings figure that is materially wrong.

Substituting your own numbers

• Interior — square footage × baseline W/sq ft × annual operating hours
• Exterior — connected kW × annual operating hours, typically 4,380 on photocell control

Apply reduction percentages separately — do not blend them

Sum, divide by 1,000 for annual AECs

Multiply by price — $23 spot or $26.92 weighted average

A 200,000 square foot property with modest exterior lighting is looking at roughly 550 to 650 MWh annually. A million square foot campus with structured parking can exceed 3,000 MWh.

Frequently asked questions

Does lighting controls commissioning affect eligibility?

Savings claimed from controls must be substantiated. Commissioning documentation showing sensors and schedules are configured and functioning supports the claim.

Can buildings retrofitted in different years be aggregated?

Yes, provided each remains operational and verifiable. Measure life runs from each building's installation date, so a portfolio may have staggered remaining lives.

What if some buildings claimed rebates and others did not?

Both can be included. Rebate documentation supports the buildings it covers; the others need independent savings substantiation.

Does exterior lighting on a separate meter complicate registration?

Separate metering generally helps. Isolated measurement is cleaner than allocating within a combined meter.

How does this interact with a tenant's own submetered improvements?

Where a tenant funded and submetered its own retrofit, that measure and its attributes may sit with the tenant. Worth mapping before an application.

Model your facility

Substitute your own numbers, or send us the inputs and we will run it — including the assumptions most estimates get wrong.