When Residential Tariffs Fail to Reward Flexibility: Modelling Prosumers Under Realistic Tariff Structures

Abstract

Residential prosumers combining rooftop PV, stationary batteries (BESS), and vehicle-to-grid (V2G)-capable EVs require distribution tariffs that reward, rather than suppress, flexibility. This paper quantifies how the structural design of monthly peak-demand charges affects prosumer operations in Sweden. Using the EL1XR-Opt MILP framework, we co-optimise PV, battery dispatch, EV smart charging, and V2G under an explicit tariff model over a full year of hourly data across ten representative households from a low-voltage network in the SE3 bidding zone; perfect-foresight results are upper bounds on achievable cost reduction. Five tariff scenarios decompose the current Swedish effekttariff (monthly power-demand charge) into three design dimensions: charge level (μpk), selection window (daily-reset vs. monthly-pool), and averaging intensity (|K|). The peak charge reshapes rather than uniformly suppresses DER dispatch: BESS throughput remains substantial while V2G is disproportionately constrained. More strikingly, structural alternatives at the same nominal charge rate raise household costs by 33–38% and penalise inflexible households most severely, exposing a significant tariff equity risk. Halving the charge rate (μpk÷2) is the sole Pareto-favourable lever: it reduces costs by 11.2% with near-unchanged grid peak. These findings provide quantitative evidence for the tariff parameters that Swedish regulators and DSOs must calibrate before the 2027 rollout.