On the Optimality of Procrastination Policy for EV charging under Net Energy Metering

TL;DR

This paper demonstrates that a procrastination threshold policy for EV charging, co-optimized with renewable energy and flexible demands, is optimal under certain conditions, with simple computation and near-optimal performance.

Contribution

It establishes the optimality of procrastination policies in EV charging with renewable integration and provides practical methods for threshold computation.

Findings

Procrastination threshold policy is optimal for EV charging with flexible demands.

Net consumption is a two-threshold piecewise linear function of renewable generation.

Myopic policy performs within 0.5-7.5% of the oracle upper bound.

Abstract

We consider the problem of behind-the-meter EV charging by a prosumer, co-optimized with rooftop solar, electric battery, and flexible consumptions such as water heaters and HVAC. Under the time-of-use net energy metering tariff with the stochastic solar production and random EV charging demand, a finite-horizon surplus-maximization problem is formulated. We show that a procrastination threshold policy that delays EV charging to the last possible moment is optimal when EV charging is co-optimized with flexible demand, and the policy thresholds can be computed easily offline. When battery storage is part of the co-optimization, it is shown that the net consumption of the prosumer is a two-threshold piecewise linear function of the behind-the-meter renewable generation under the optimal policy, and the procrastination threshold policy remains optimal, although the thresholds cannot be computed easily. We propose a simple myopic solution and demonstrate in simulations that the performance gap between the myopic policy and an oracle upper bound appears to be 0.5-7.5%.