Consider the following:

1. Battery storage

2. Biomass generators

3. Fuel cells

4. Rooftop solar photovoltaic units

How many of the above are considered “Distributed Energy Resources”?

The correct option is All four.

Distributed Energy Resources (DERs) refer to small-scale, decentralized energy generation, storage, and management technologies that are typically located close to the site of electricity consumption (on the customer side of the meter) or directly connected to a local distribution grid, rather than the centralized high-voltage transmission system.

Let us analyze each of the given items to understand why they are classified as DERs:
1. Battery storage: Battery energy storage systems (BESS) store electricity locally and release it when demand is high, during outages, or when renewable generation is low. Because they function as localized energy storage units connected at the distribution level, they are classified as DERs.
2. Biomass generators: Biomass systems generate electricity and heat locally using organic materials. When deployed at a localized, community, or individual facility scale to supply nearby loads, they serve as distributed generation resources.
3. Fuel cells: Fuel cells produce electricity and heat through clean electrochemical reactions, typically running on hydrogen or natural gas. They are commonly installed onsite at commercial facilities, industrial sites, or residential buildings, making them a standard form of DER.
4. Rooftop solar photovoltaic units: Rooftop solar panels are one of the most common and recognizable examples of distributed generation. They generate electricity directly on the roofs of buildings to meet local demand, with any surplus often fed back into the local distribution grid.

Since all four options qualify as decentralized energy generation or storage technologies located close to the point of consumption, they are all considered Distributed Energy Resources.