What Is REopt?
NREL's REopt® tool evaluates the cost savings and resilience benefits of solar, wind, and battery storage at a facility or group of facilities.
REopt helps users identify the size and dispatch schedule for an onsite energy system that will minimize a site's electricity costs. The tool also estimates the amount of time a system will provide power to a facility during a grid outage.
REopt uses mathematical optimization to recommend the optimal size and dispatch for any combination of several energy technologies, including solar, wind, combined heat and power, chilled water storage, fuel generators, grid electricity, geothermal heat pumps, and battery storage. Users are prompted for a few simple inputs about the site, such as location, utility rate, and energy consumption. More advanced users can edit the model's default values such as technology costs and efficiencies, analysis horizon, and financial parameters. After running, REopt provides a summary results table, an interactive dispatch graph, and detailed outputs on resilience and emissions outcomes.
Key Terms
The amount of electricity, measured in watts or kilowatts, required to power a facility at any given moment. A facility's electricity load often varies over hours, days, and weeks. All onsite equipment requiring electricity contributes to a facility's overall load, but a subset of equipment may represent the facility's critical load—the amount of electricity needed to power equipment without which the facility cannot provide its essential services.
A facility's total electrical consumption, measured in kilowatt-hours, can be aggregated over a day, month, or year by multiplying load (kilowatts) by the number of hours that load operates. Electrical load is one of the key inputs for a REopt analysis.
Utilities charge for the energy consumed at a facility over time using a variety of rate structures that significantly impact the cost-effectiveness of onsite energy systems. Utility rates include energy charges—the cost of the total energy consumed over a bill period ($/kWh) and demand charges—an additional cost for the peak amount of energy consumed at any moment during the bill period (kW).
Describes what each energy technology at a facility is doing during each hour of the year. Energy technologies can provide electricity for a facility's immediate needs, charge batteries for future electricity use, or send electricity into the larger grid, depending on which activity is most cost-effective for the facility. For example, if the cost of electricity varies throughout the day, a battery might charge while electricity is cheaper and discharge when electricity is more expensive.
The length of time an on-site energy system will reliably operate after installation, typically estimated at 25-30 years for technologies like solar. The lifecycle cost of energy refers to the amount spent on energy at the site over this period. If you do not have on-site technologies like solar and storage, your lifecycle cost of energy is the amount you spend on your monthly utility bills over 25-30 years. With on-site technologies, the lifecycle cost of energy includes the cost to buy and maintain the technologies, as well as your reduced utility bill costs.
REopt also allows users to explore how solar, storage, diesel generators, and other technologies can increase a site's resilience during a grid outage. The tool can size systems to sustain critical loads during user-specified outages; it also calculates the probability of surviving outages of varying length that occur during different times of the year.
Check out this quick video walkthrough of REopt's basic features.
Critical Facilities
Critical facilities like hospitals, pharmacies, schools, or water treatment plants require electricity to function and often rely on diesel generators to operate during power outages. However, traditional generators require fuel that may be unavailable or expensive during supply chain interruptions, contribute to rising greenhouse gas emissions, and can fail without consistent maintenance. Advances in renewable energy and storage technology offer increasingly cost-effective options for backup energy systems that increase community resilience by ensuring that critical facilities provide key services even when the grid is unreliable. REopt can identify the optimal onsite energy system to improve resilience at a critical facility.
Below, explore example REopt results for a handful of critical facilities across the U.S.
Try this: Which state facilities have onsite energy systems that provide both resilience and cost savings?
Producing results like these requires users to provide data about a facility's energy use. Next week, we'll start discussing these data inputs, beginning with electricity load—why it's important, how to measure it, and how to enter it in REopt.