Techno-Economic Analysis of Integrated PV-Battery-EV Systems with Price-Responsive Control under Dynamic Pricing: A Scottish Residential Case Study

Abstract

This study evaluated the techno-economic performance of integrated photovoltaic-battery-electric vehicle systems in UK residential applications, with a focus on Scottish conditions where solar resources are limited. The baseline for this study is a cottage in Fintry, Scotland with an existing 12 kW heat pump system (HP) . The property is currently being considered for the addition of solar PV, battery storage, and electric vehicle charging infrastructure. The analysis specifically excluded thermal storage from the HP system, operating without hot water tank to isolate the impacts of electrical battery storage, aligning with emerging zero-bill home concepts that prioritize electrical solutions. Using a case study property in Fintry, Scotland with a 6.37 kWp PV system, three scenarios were analyzed: standalone PV system, integrated PV with battery storage and EV charging, and smart battery control under dynamic pricing. The analysis evaluated performance under flat-rate, Economy 7, and Agile Octopus dynamic tariffs using PV*SOL simulation software and Python-based control algorithms to assess technical and economic performance over a 25-year period. Results showed that control strategy selection was more important than component capacity in determining economic viability. Among the control strategies evaluated, the integrated PV-battery-EV system where PV first supplies household demand, then charges EV and battery when sufficient surplus exists (with batteries charging exclusively from solar while EVs can also charge from grid) achieved 8.90% internal rate of return and 13.4 year payback despite lower annual electricity cost savings (£1,107) compared to Night Charging configurations (where batteries charge from grid during off-peak hours for later discharge) which achieved £1,294 annually but required three battery replacements costing £28,500 over the project lifetime. This solar-optimized configuration achieved 93.6% self-consumption rate compared to 47.5% for standalone PV systems, demonstrating the combined benefits of coordinated storage systems. Price-responsive battery control under Agile Octopus dynamic tariff reduced annual electricity costs by up to 41.5% (£2,183 savings) compared to grid-only supply, though this optimization reduced solar self-consumption from 93.6% to 70-72% as the control algorithms prioritized low-price grid charging over solar utilization. The study found that current UK tariff structures, with only 1.5% difference between import and export rates, prevent profitable battery arbitrage (time-shifting energy for price differential gains). After accounting for 93.7% round-trip efficiency (meaning 6.3% of stored energy is lost), systems lose £0.008 per kWh cycled through the battery. The research demonstrates that viewing batteries as self-consumption tools rather than arbitrage devices, combined with conservative cycling strategies that preserve battery longevity, makes these integrated systems economically viable even in Scotland with its challenging solar conditions. The findings are specific to the case study, input parameters chosen, and control strategies investigated, but also provide useful insights in general. The methodology developed in this project provides a useful template for further work.