REopt Optimizes Residential Solar-Plus Technologies Behind The Meter
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.
NREL conference paper: Valuing Energy Efficiency and Distributed Energy Resources in the Built Environment
Applied Energy journal article: Solar Plus: Optimization of Distributed Solar PV through Battery Storage and Dispatchable Load in Residential Buildings
Science Trends online article: Thinking Creatively about Residential Solar PV System Optimization: The Solar Plus Approach
Applied Energy journal article: Solar Plus: A Review of the End-User Economics of Solar PV Integration with Storage and Load Control in Residential Buildings
Solar Plus: A Holistic Approach to Distributed Solar PV:
NREL fact sheet: Federal Tax Incentives for Battery Storage Systems
NREL poster: Optimizing Energy Storage Economics
Department of Energy Solar Energy Technologies Office
Rocky Mountain Institute