What Are Renewable Energy Credits?

Most people meet renewable energy credits through a utility bill, a sustainability report, or a solar quote — and in each case the explanation stops short of what the thing actually is. A renewable energy credit is not a discount, a tax credit, or a share of a wind farm. It is a certificate that records one specific fact: that a measured quantity of electricity was produced by a qualifying resource, or in some states that a measured quantity was never consumed at all. That certificate can then be sold separately from the electricity itself.

The unit: one megawatt-hour, one certificate

Every renewable energy credit represents one megawatt-hour. A system that produces 1,000 MWh in a year produces 1,000 certificates. Nothing about that is negotiable — the price moves, the count does not. This is why credit revenue scales with output rather than with what the system cost to build, and why two similar buildings can earn very different amounts depending on how much they actually generate or save.

What a credit certifies, and what it does not

A renewable energy credit carries the environmental attribute of the generation — the claim that the megawatt-hour was renewable. It does not carry the electricity. The two separate at the meter and travel to different buyers. The power flows onto the grid and is consumed by whoever is nearest; the attribute is recorded in a registry and sold to whoever needs to make a claim or satisfy an obligation. Once a certificate is retired, it is spent, and that megawatt-hour cannot be counted again by anyone.

How renewable energy certificates work, from meter to sale

The lifecycle has four steps and they always run in the same order. First, the resource is certified as eligible by the state programme that will recognise its credits — eligibility is a state determination, not a registry one. Second, the owner opens an account in the regional tracking registry and registers the facility under the certification number the state issued. Third, metered production or verified savings are reported on a recurring basis, and the registry mints certificates against those readings. Fourth, the certificates are sold — bilaterally, through a broker, through an aggregator, or on an exchange — and retired by the buyer.

The order matters more than it looks. Certificates are generally issued forward from the date a complete application is on file, not backward to the date the equipment was switched on. Pennsylvania applies that principle with one distinction worth knowing: efficiency and other Tier II projects run from the complete filing under 52 Pa. Code § 75.63(i), while solar runs from the later of the filing and the utility's approval of the system. Either way, two years of operating unregistered is not two years of banked credits — that output was never certificated, and it cannot be recovered.

Who issues renewable energy certificates

Two different bodies are involved, and conflating them is the most common source of confusion. The state decides whether a resource qualifies and issues a certification number. The registry issues the certificates themselves and tracks every transfer and retirement. In the PJM region that registry is the Generation Attribute Tracking System operated by PJM Environmental Information Services, usually shortened to PJM-GATS. Other regions run their own — M-RETS in the Midwest, NEPOOL-GIS in New England, and ERCOT's system in Texas. A certificate stays bound to the state that certified it, which is why its geography is fixed at birth and cannot be re-badged later. A fuller walkthrough of that registry is here.

Compliance credits and voluntary credits are different instruments

This distinction causes the most expensive mistakes. A compliance certificate satisfies a legal obligation placed on electricity suppliers by a state portfolio standard. A voluntary certificate is bought by an organisation that wants to make a clean-energy claim but faces no statutory requirement to do so. Both are measured in megawatt-hours and both sit in the same registries, but they are not interchangeable and they do not trade anywhere near the same price. National voluntary certificates have historically changed hands in the low single digits per megawatt-hour, while Pennsylvania compliance credits have recently cleared in the twenties and thirties. Quoting one as evidence for the other is simply wrong, and the figures and sources are set out in the comparison of Pennsylvania's two tiers.

Renewable energy credits and carbon offsets are not the same thing

A renewable energy credit is denominated in energy: one megawatt-hour generated or saved. A carbon offset is denominated in mass: one metric tonne of carbon dioxide equivalent avoided, reduced or removed. They answer different questions, sit in different registries, and support different claims. An organisation reporting emissions from purchased electricity uses certificates; one addressing emissions it cannot electrify may use offsets. A single project can sometimes produce both, but the attributes have to be allocated — selling the energy attribute and the carbon attribute of the same megawatt-hour to two different buyers is double counting.

Solar renewable energy certificates

A solar renewable energy certificate, or SREC, is a renewable energy credit that only solar generation can produce. The separate name exists because many state portfolio standards carve out a dedicated share of the obligation for solar specifically, which creates a second, smaller market alongside the general one. Because that carve-out is a fixed slice of a much larger obligation, solar certificates often clear at a premium to non-solar credits in the same state. Pennsylvania runs such a carve-out inside its Tier I obligation. Owners of Pennsylvania solar can see how registration, reporting and sale work on the solar credit page.

What Pennsylvania calls them: alternative energy credits

Pennsylvania's statute does not use the phrase renewable energy credit at all. The Alternative Energy Portfolio Standards Act of 2004 created alternative energy credits, or AECs, and split them into two tiers. Tier I holds the resources most people picture as renewable — solar, wind, low-impact hydropower, geothermal, biomass, biologically derived methane, fuel cells and coal mine methane. Tier II holds a wider and less obvious set: waste coal, large-scale hydropower, municipal solid waste, wood pulping by-products, integrated gasification, and the one that matters most to commercial building owners — demand-side management, meaning verified energy efficiency. In market conversation both are still called RECs. The names differ; the instrument does not.

The Tier II route is the unusual one, and it is worth understanding because it is the only path that pays a building owner for electricity never consumed rather than electricity generated. A lighting or HVAC retrofit with documented savings earns certificates on the same mechanical basis that a solar array earns them on output. That path is covered in what Tier II credits are and how they generate revenue, and the choice between the two in Tier II AEC versus SREC.

Where to go next

For the full commercial and industrial treatment — tier eligibility side by side, the certification sequence, current Pennsylvania values and the channels credits are sold through — start with the guide to Pennsylvania alternative energy credits. If a project is already built and running, the first question worth answering is not what certificates are worth but whether registration has happened — because under the filing rule above, every unregistered month is one that cannot be recovered.

What Pennsylvania solar credits actually sell for, as distinct from what they are, is set out in Pennsylvania SREC prices.