REopt Optimizes Residential Solar-Plus Technologies Behind The Meter

REopt compares solar PV and “solar-plus” customer load profiles, grid net load, and solar PV output. Illustration from NREL

The REopt^® platform can determine the optimal mix and size of solar photovoltaics (PV) and “solar-plus” technologies to lower the life cycle cost of energy for a number of post-net metering residential utility tariffs (including time-of-use [TOU] and demand tariffs). “Solar-plus” uses solar PV in combination with energy storage and controllable devices—such as smart domestic water heaters, smart air conditioning (AC) units, and electric vehicles—to help customers increase solar self-consumption and realize value from a larger share of their system’s output behind the meter.

For Hawaii’s TOU residential tariff—where no energy export is allowed—the solar-plus approach increases net present value by a factor of three relative to the stand-alone solar PV approach. The smart AC unit and smart domestic water heater are dispatched each day to pre-cool the home and pre-heat water with solar PV output. Any excess output remaining after pre-cooling and water heating is delivered to a battery, which is dispatched to further reduce TOU rates. Customers can use solar-plus technologies to take advantage of excess solar PV output, increasing their cost-optimal system size, reducing system curtailment, and increasing the value of their solar PV system.

The results indicate that the solar-plus approach improves the customer economics of solar PV for tariffs that include demand or TOU components, or for less-than-retail rate net metering. The solar-plus approach may become an increasingly viable model for optimizing solar PV customer economics in a post-net metering environment.

"Solar-plus" technologies combine to increase solar self-consumption. Illustration by Eric O'Shaughnessy, NREL 66299