Energy Dictionary

Definitions and explainers for core energy industry terms, units and concepts.

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What Is a Battery Energy Storage System (BESS)?

What Is a Battery Energy Storage System (BESS)?

Last updated: November 9, 2026 A battery energy storage system (BESS) is a grid-connected installation of rechargeable batteries, usually lithium-ion, that stores electricity when it...

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What Is Henry Hub and Why Does It Set U.S. Gas Prices?

What Is Henry Hub and Why Does It Set U.S. Gas Prices?

Last updated: November 9, 2026 Henry Hub is a natural gas pipeline interconnection point in Erath, Louisiana, that serves as the official delivery point for...

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What Is a Power Purchase Agreement (PPA)?

What Is a Power Purchase Agreement (PPA)?

Last updated: November 2, 2026 A power purchase agreement (PPA) is a long-term contract between an electricity buyer and a generator that locks in a...

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What Are Upstream, Midstream and Downstream in Oil and Gas?

What Are Upstream, Midstream and Downstream in Oil and Gas?

Last updated: November 2, 2026 Upstream, midstream and downstream are the three broad segments of the oil and gas industry. Upstream covers exploration and production...

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What Is LCOE (Levelized Cost of Electricity)?

What Is LCOE (Levelized Cost of Electricity)?

Last updated: October 26, 2026 The levelized cost of electricity (LCOE) is the average cost, in dollars per megawatt-hour ($/MWh), of building and running a...

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What Is a Small Modular Reactor (SMR)?

What Is a Small Modular Reactor (SMR)?

Last updated: October 26, 2026 A small modular reactor (SMR) is an advanced nuclear reactor design that produces up to 300 megawatts of electricity (MWe)...

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What Is Carbon Capture and Storage (CCS)?

What Is Carbon Capture and Storage (CCS)?

Last updated: October 19, 2026 Carbon capture and storage (CCS) is a set of technologies that capture carbon dioxide (CO2) before it reaches the atmosphere...

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What Is Green Hydrogen and How Is It Made?

What Is Green Hydrogen and How Is It Made?

Last updated: October 19, 2026 Green hydrogen is hydrogen gas produced by splitting water into hydrogen and oxygen in an electrolyzer powered by renewable electricity,...