Colorado Regulation 28 gives building owners four pathways to demonstrate building performance compliance. Pathways 1, 2, and 3 are all variations on reducing your building’s energy consumption. Pathway 4 is different: it lets you meet your compliance obligation through renewable energy — specifically by offsetting your building’s greenhouse gas emissions with clean electricity generation or procurement.

For building owners whose properties face significant barriers to energy efficiency improvement — high-density occupancy, process loads, unusual building systems, lease structures that limit capital investment — Pathway 4 can be the most practical route to compliance. It can also be the right choice for owners who want compliance certainty before the December 2026 or 2027 deadlines without waiting for efficiency projects to be completed and verified.

This guide explains exactly how Pathway 4 works under 5 CCR 1001-32, what renewable energy options qualify, and what you need to do to use this pathway.

What Pathway 4 Requires

Under Regulation 28, Pathway 4 compliance requires demonstrating that your building’s energy use is fully offset by zero-carbon electricity — either generated on-site or procured through qualifying mechanisms. The regulation’s technical language requires that the renewable energy offset match the building’s energy consumption on an annual basis.

CDPHE has provided guidance (through the Colorado Energy Office and AQCC rulemaking) that Pathway 4 qualifying mechanisms include:

  1. On-site renewable generation — solar PV systems installed on or adjacent to the building that generate electricity consumed at the building
  2. Renewable Energy Credits (RECs) — unbundled or bundled RECs from qualifying renewable generators, matched to the building’s consumption
  3. Green tariff programs — utility-administered programs that supply renewable electricity through the existing grid connection
  4. Power Purchase Agreements (PPAs) and Virtual PPAs (VPPAs) — contracts for renewable electricity from off-site generators

Not all of these mechanisms are treated equally by CDPHE under the regulation. On-site generation is the most straightforward to document. RECs and green tariffs require careful attention to how the regulation defines and verifies claims.

On-Site Solar: The Most Documented Pathway 4 Option

Installing solar PV on your building or on-site property is the cleanest Pathway 4 implementation from a compliance documentation standpoint. Generation is measured directly, consumption is measured directly, and the offset calculation is straightforward.

System Sizing for Full Compliance

To satisfy Pathway 4 through on-site solar, your system needs to generate electricity equal to or greater than your building’s annual energy consumption — expressed as kWh. This is a meaningful sizing requirement. A fully solar-offset commercial building in Colorado’s climate typically requires:

  • Rooftop solar at high irradiance locations (Denver, Front Range): approximately 5–7 watts of DC capacity per square foot of building floor area for a well-insulated mid-rise office
  • Buildings with high plug loads, poor insulation, or large floor plates relative to roof area may require more capacity than the rooftop can accommodate

For most commercial buildings over 50,000 square feet, full on-site solar offset is technically challenging on rooftop alone — the roof area is insufficient relative to floor area and load. This pushes owners toward carport solar, ground-mount arrays on adjacent land, or combining on-site generation with off-site mechanisms.

Colorado Incentives for On-Site Solar

The economics of commercial solar in Colorado are among the best in the country, driven by high solar irradiance, strong federal incentives, and Xcel Energy’s net metering programs:

Federal Investment Tax Credit (ITC): The Inflation Reduction Act extended and expanded the ITC for commercial solar. In 2026, commercial solar projects qualify for a 30% tax credit on installed system cost, with additional bonus credits (up to 10% each) for projects in energy communities or using domestic content. For a $500,000 solar installation, the base ITC alone is worth $150,000.

Xcel Energy Solar*Rewards Commercial: For commercial buildings in Xcel territory (most of the Front Range including Denver, Boulder, Fort Collins, Lakewood, and Colorado Springs), the Solar*Rewards program pays a per-kWh incentive for solar generation. Current rates vary by program tier — contact Xcel’s renewable energy team for current incentive schedules.

Colorado C-PACE: Solar installations are fully eligible for Colorado C-PACE financing — long-term, fixed-rate financing repaid through property tax assessments. For owners who want the compliance benefits of solar without large upfront capital, C-PACE is often the financing mechanism that makes the project work.

Accelerated Depreciation (MACRS): Commercial solar qualifies for 5-year MACRS depreciation, providing additional tax benefit for profitable building owners.

Renewable Energy Credits (RECs): Flexibility With Documentation Requirements

Renewable Energy Credits represent the environmental attributes of one megawatt-hour of electricity generated from a renewable source. Under Pathway 4, purchasing RECs allows you to claim renewable energy offset without installing generation on your property.

How RECs Work Under Regulation 28

Each REC is a tradeable certificate that certifies one MWh of renewable electricity was generated and injected into the grid. To claim Pathway 4 compliance using RECs, you need to:

  1. Determine your building’s annual electricity consumption in MWh from your benchmarked Portfolio Manager data
  2. Purchase RECs in a quantity matching that consumption
  3. Retire the RECs in your name through a tracking system (typically WREGIS — the Western Renewable Energy Generation Information System, which is the standard registry for Colorado)
  4. Document the retirement for CDPHE compliance reporting

CDPHE guidance requires that RECs used for Regulation 28 Pathway 4 compliance be current-year RECs — you cannot use RECs generated in prior years to satisfy your compliance obligation. They must also be retired (not resold), meaning you formally take them out of circulation in your name.

REC Sourcing and Cost

RECs can be sourced through several channels:

Utilities: Xcel Energy and Black Hills Energy both offer voluntary renewable energy products bundled with utility service that include REC retirement on your behalf. These are typically sold as a premium per-kWh above your standard rate.

REC brokers and marketplaces: Unbundled RECs (RECs sold separately from the underlying electricity) are available through energy brokers at lower cost than utility green products. Colorado wind RECs have historically traded in the $2–$8/MWh range, though prices fluctuate. For a 100,000 sq ft office building consuming 1,500 MWh annually, unbundled REC cost would be approximately $3,000–$12,000/year.

Important caveat: CDPHE has indicated that unbundled RECs from distant regions (e.g., wind RECs from the Southeast or mid-Atlantic) may face additional scrutiny compared to RECs from Colorado or regional generators. Use Colorado or WECC (Western Interconnection) region RECs to minimize compliance risk.

Green Tariff Programs: Utility-Administered Renewable Electricity

Green tariff programs allow commercial customers to receive renewable electricity through their existing utility connection under a rate schedule that delivers verified renewable energy. Unlike purchasing unbundled RECs separately, green tariffs bundle the renewable attributes with the electricity supply.

Xcel Energy’s Renewable*Connect Program

Xcel Energy offers Renewable*Connect, a green tariff program that allows commercial customers to subscribe to blocks of renewable electricity (typically wind or solar). The renewable attributes — including RECs — are retired on the customer’s behalf, and Xcel provides documentation of the renewable energy supplied.

For Regulation 28 Pathway 4, Renewable*Connect subscriptions can satisfy the renewable energy requirement if the subscription covers 100% of your building’s annual electricity consumption. Xcel’s program documentation includes the REC retirement records needed for CDPHE compliance reporting.

Renewable*Connect pricing varies by subscription term and block size — contact Xcel’s commercial renewable energy team for current rate sheets.

Black Hills Energy

Commercial customers in Black Hills Energy territory (Pueblo, Colorado Springs area, and portions of southeastern Colorado) can access renewable options through Black Hills’ voluntary renewable programs. Contact Black Hills commercial services for current program availability and pricing.

Virtual Power Purchase Agreements (VPPAs): For Larger Portfolios

VPPAs are financial contracts between a building owner (or portfolio owner) and a renewable energy developer. Unlike a traditional PPA where you receive renewable electricity through a dedicated line, a VPPA is a financial settlement — you pay a fixed strike price for renewable electricity, and the generator sells the electricity on the market. The difference (positive or negative) settles financially, and you receive the RECs from the generator’s output.

VPPAs are most commonly used by large commercial portfolios — companies with multiple buildings and enough aggregate load to justify the contract complexity. Minimum VPPA sizes are typically 5–10 MW, making them impractical for single-building owners.

If you own a portfolio of Colorado commercial properties all subject to Regulation 28, a VPPA structured around your aggregate load could provide both compliance coverage and potential economic benefit if wholesale electricity prices exceed your strike price. This requires working with a renewable energy advisor or energy counsel experienced in Colorado’s power market.

Documentation Requirements for Pathway 4

Regardless of which Pathway 4 mechanism you use, CDPHE requires documentation demonstrating that your renewable energy procurement covers your building’s consumption for the compliance year. Maintain records of:

  • Annual building energy consumption from Portfolio Manager (kWh by fuel type)
  • REC retirement certificates from WREGIS or equivalent registry, showing retirement in your name
  • Utility program enrollment documentation for green tariffs
  • Solar generation records if using on-site generation
  • Any PPA or VPPA contract summaries

Start assembling this documentation now rather than scrambling at the compliance deadline. CDPHE compliance filings require organized, verifiable records — not just a statement that renewable energy was used.

Is Pathway 4 Right for Your Building?

Pathway 4 is the right choice when:

  • Your building’s energy consumption is driven by factors that can’t easily be reduced (process loads, tenant equipment, high occupancy density)
  • You want compliance certainty before your December 2026 or 2027 deadline without waiting for efficiency projects to complete and be verified
  • You have sufficient roof or adjacent land area to make on-site solar viable
  • Your lease structure prevents capital investment in building systems but allows renewable energy procurement

It’s less appropriate when your building could reach Pathway 1 EUI compliance with modest efficiency improvements that also reduce operating costs — in that case, efficiency investment produces both compliance and ongoing savings, while Pathway 4 is an ongoing annual cost.

For most buildings, the answer isn’t exclusively Pathway 4 or Pathway 1 — a combination of efficiency improvements and renewable energy procurement provides compliance flexibility and reduces the amount of renewable energy needed for full offset.

For questions about which pathway makes sense for your specific building, see our compliance pathways guide or contact us for a free consultation.