[Paper Review] Integrating Distributed Energy Resources: Optimal Prosumer Decisions and Impacts of Net Metering Tariffs

Ahmed S. Alahmed, Lang Tong|arXiv (Cornell University)|Apr 12, 2022

Smart Grid Energy Management47 references4 citations

TL;DR

This paper develops an analytical framework for optimal prosumer energy consumption under an inclusive Net Energy Metering X (NEM-X) tariff model, which unifies existing and proposed NEM policies. It derives a two-threshold optimal consumption policy with near-closed-form solutions, enabling practical energy management under stochastic distributed energy resources (DERs) and dynamic pricing, and quantifies welfare, cross-subsidies, and long-term adoption under NEM and feed-in tariff (FiT) designs.

ABSTRACT

The rapid growth of the behind-the-meter (BTM) distributed generation has led to initiatives to reform the net energy metering (NEM) policies to address pressing concerns of rising electricity bills, fairness of cost allocation, and the long-term growth of distributed energy resources. This article presents an analytical framework for the optimal prosumer consumption decision using an inclusive NEM X tariff model that covers existing and proposed NEM tariff designs. The structure of the optimal consumption policy lends itself to near closed-form optimal solutions suitable for practical energy management systems that are responsive to stochastic BTM generation and dynamic pricing. The short and long-run performance of NEM and feed-in tariffs (FiT) are considered under a sequential rate-setting decision process. Also presented are numerical results that characterize social welfare distributions, cross-subsidies, and long-run solar adoption performance for selected NEM and FiT policy designs.

Motivation & Objective

• To address the economic and engineering challenges posed by evolving net metering (NEM) policies and their impact on prosumer behavior and utility cost recovery.
• To develop a unified analytical model—NEM-X—that captures existing and proposed NEM tariff designs, including NEM 1.0, 2.0, 3.0, and FiT structures.
• To characterize optimal prosumer consumption decisions under stochastic behind-the-meter (BTM) distributed energy resources (DERs) and dynamic pricing.
• To evaluate the short- and long-run impacts of NEM-X and FiT policies on social welfare, cross-subsidies, and DER adoption dynamics.
• To provide a decision framework for regulators and energy management systems that balances fairness, efficiency, and sustainable DER growth.

Proposed method

• Proposes an inclusive NEM-X tariff model that generalizes classical NEM, FiT, and net purchase/sale tariffs into a single parametric framework.
• Derives a two-threshold optimal consumption policy for prosumers, enabling near-closed-form solutions for energy allocation between local use and grid export.
• Applies model-predictive control (MPC) to handle stochasticity in BTM generation, leveraging the structure of the optimal policy for real-time decision-making.
• Introduces a sequential rate-setting model where utility tariffs are endogenously determined based on DER adoption levels and break-even cost constraints.
• Uses analytical expressions for prosumer surplus under NEM and FiT to compare economic outcomes across policy designs.
• Employs a system-theoretic regulator model to simulate long-run welfare, cross-subsidy, and market potential under different NEM-X parameterizations.

Experimental results

Research questions

• RQ1 How does the optimal consumption policy for prosumers change under different NEM-X tariff structures, particularly with differentiated import and export rates?
• RQ2 What is the impact of stochastic behind-the-meter (BTM) generation on the performance of optimal energy management strategies under NEM-X?
• RQ3 How do NEM and FiT policies compare in terms of social welfare distribution, cross-subsidy, and long-term DER adoption potential?
• RQ4 What are the long-run equilibrium outcomes of NEM-X policies when utility tariffs are set endogenously based on adoption levels and cost recovery?
• RQ5 How do changes in export compensation rates (e.g., NEM 2.0 vs. NEM 3.0) affect prosumer surplus and the economic viability of solar adoption?

Key findings

• The optimal prosumer consumption policy under NEM-X exhibits a two-threshold structure, enabling near-closed-form solutions that are practical for real-time energy management systems.
• Under NEM 1.0, prosumers receive full retail compensation for exported energy, leading to significant cross-subsidies from non-prosumers, which increases with higher DER penetration.
• Reducing the export compensation rate (π⁻) in NEM 2.0 and NEM 3.0 policies significantly reduces prosumer surplus and slows long-term solar adoption, especially when combined with high import prices.
• Numerical results show that FiT policies with export rates aligned to avoided costs can maximize social welfare and eliminate cross-subsidies, but require discriminatory pricing between consumers and prosumers.
• The model predicts that under NEM 1.0, peak demand can be deferred by nearly four months due to optimized local consumption, improving grid reliability.
• The study reveals that the price differential (π⁺ − π⁻) and time-of-use (TOU) rate parameters are critical in determining bill savings for solar-plus-storage systems, with higher differentials increasing economic incentives for storage integration.