HOMER Grid is an optimization tool for investigating whether investing in distributed, behind-the-meter, grid-connected technologies can lower electricity costs through demand charge reduction and energy arbitrage. HOMER Grid is based on HOMER Pro, so it includes many of the same elements, but the optimization goal takes demand charges into account. HOMER Grid uses the Genability tariff database to make it easy for customers to model a particular location. HOMER Grid users can also create their own tariff structures.

Homer Grid simplifies the task of evaluating designs for grid-connected power systems. When you design a power system, you must make many decisions about the configuration of the system, such as:

•Which components are best for this system?

•How many and what size of each component are most efficient?

The large number of technology options, complex tariff structures, variation in costs, and availability of energy resources make these decisions difficult. HOMER Grid's optimization and sensitivity analysis algorithms make it easier to evaluate the many possible system configurations.

To use HOMER Grid, you select and enter information under the Design button to provide the model with inputs, including components (e.g., generator, storage, and solar), component costs, and resource availability.

When you click the Results button, HOMER Grid uses these inputs to simulate different system configurations, or combinations of components, and generates results that you can view as a list of feasible configurations sorted by net present cost under the Results button. HOMER Grid also displays simulation results in a wide variety of tables and graphs that help you compare configurations and evaluate them on their economic and technical merits. You can export the tables and graphs for use in reports and presentations.

You can further use the model to perform sensitivity analyses to explore the effects that changes in factors, such as resource availability and economic conditions, might have on the cost-effectiveness of different system configurations. To perform a sensitivity analysis, you provide HOMER Grid with sensitivity values that describe a range of resource availability and component costs. The software simulates each system configuration using the range of values. You can use the results of a sensitivity analysis to identify the factors that have the greatest impact on the design and operation of a power system. You can also use HOMER Grid's sensitivity analysis results to answer general questions about technology options to inform planning and policy decisions.

HOMER Grid simulates energy systems, shows system configurations optimized by cost, and provides sensitivity analyses.

HOMER Grid simulates the operation of a system by making energy balance calculations in each time step (interval) of the year. For each time step, HOMER compares the electric and thermal demand in that time step to the energy that the system can supply in that time step, and calculates the flow of energy to and from each component of the system. For systems that include batteries or fuel-powered generators, HOMER Grid also decides in each time step how to operate the generators and whether to charge or discharge the batteries.

HOMER Grid performs these energy balance calculations for each system configuration that you want to consider. It then determines whether a configuration is feasible, (i.e., whether it can meet the electric demand under the conditions that you specify), and estimates the cost of installing and operating the system over the lifetime of the project. The system cost calculations account for costs such as capital, replacement, operation and maintenance, fuel, and interest.

HOMER Grid has two optimization algorithms. The original grid search algorithm simulates all of the feasible system configurations defined by the Size your own component sizing options. The new HOMER Optimizer® uses a proprietary derivative-free algorithm to search for the least-cost system. HOMER Grid then displays a list of configurations, sorted by net present cost (sometimes called life-cycle cost), that you can use to compare system design options.

When you define sensitivity variables as inputs, HOMER Grid repeats the optimization process for each sensitivity variable that you specify. For example, if you define wind speed as a sensitivity variable, HOMER Grid simulates system configurations for the range of wind speeds that you specify.