Modeling Solar, Battery and EV Charging Together: A Verified Residential Case Study
July 17, 2026
The Engineering Challenge
As electric vehicles become a standard household load, solar designers face a new layer of complexity. A rooftop PV system can no longer be sized against a static household consumption profile alone. It must account for a variable, often unpredictable charging demand that can rival or exceed the base electrical load of the property itself. In this project, located in a residential area of Baden-Württemberg, Germany, the engineering task was to integrate a 14.4 kWp photovoltaic array, a lithium iron phosphate battery system, and a home EV charging station into one coherent, simulated energy system using PV*SOL.
The core challenge was not simply installing enough panels. It was determining how solar generation, battery storage, and EV charging interact hour by hour across a full year, using real climate data, to avoid oversizing or undersizing any single component. Without this level of simulation, EPC contractors risk delivering systems that either waste generation capacity or fail to deliver the self-consumption and cost savings the customer expects.
The Approach and Methodology
The system was modeled using PV*SOL premium 2026 with climate data for Heilbronn, Germany, sourced from PVGIS-SARAH3/ERA5 at one-hour resolution. The 14.4 kWp array consists of 32 modules split across two roof orientations, one facing west at 271 degrees and one facing east at 91 degrees, both at a shallow 10 degree tilt on an elevated mounting structure. This east-west split was itself a deliberate design decision to flatten the generation curve across the day rather than concentrating output around solar noon, which is particularly relevant when a portion of that generation needs to reach an EV charger during working hours.
A single hybrid inverter rated at 12 kW AC handles both PV strings, connected to a lithium iron phosphate battery system with 9.6 kWh of usable capacity. The electric vehicle, with a 42 kWh battery and a WLTP range of 305 km, charges through an 11 kW AC Type 2 home charging station in standard charging mode. The simulation explicitly modeled the vehicle’s annual driving requirement of just over 15,000 km against the household’s separate 4,500 kWh annual electricity consumption, allowing PV*SOL to calculate how solar, battery, and grid energy are allocated across these two distinct and competing demands.
The Results
The simulation produced a specific annual yield of 1,033.13 kWh per kWp, with a performance ratio of 88.39 percent and a shading loss of only 1.7 percent, reflecting a largely unobstructed rooftop. Total PV generator energy delivered to the AC side reached 14,573 kWh per year.
Of that generation, 3,742 kWh per year was consumed directly by the household, 1,815 kWh per year went specifically to charging the electric vehicle through the battery system, and 9,017 kWh per year was exported to the grid. This gives an overall self-consumption ratio of 38.0 percent, a figure that is meaningfully higher than what a household-only load profile would typically achieve, precisely because the EV charging demand absorbs a portion of the midday and afternoon solar surplus that would otherwise be exported.
Looking at the vehicle side specifically, the EV required 2,559 kWh per year for charging in total, of which 1,815 kWh per year, or roughly 71 percent, was covered by PV and battery energy rather than grid electricity. Of the 15,017 km driven annually, 10,651 km were effectively powered by solar energy. The simulation also quantified the resulting economic effect precisely: driving costs before PV installation were calculated at 5.28 euros per 100 km, dropping to 2.39 euros per 100 km once the solar and battery system was in place, a reduction of more than 50 percent in per-kilometer energy cost.
On the household side, the overall solar coverage of combined consumption, including EV charging, reached 78.4 percent, with the battery system cycling at only 5.0 percent of its rated capacity annually and an expected service life beyond 20 years. The full system, with an investment of 19,440 euros, achieved a calculated payback period of 8 years and 5 months and an overall capital return of 11.31 percent, with a levelized cost of electricity of 0.0709 euros per kWh.
What This Means for EPCs and Investors
This case demonstrates why EV charging can no longer be treated as an afterthought bolted onto a conventional solar design. When the charging load, battery dispatch strategy, and PV generation profile are modeled together in a single hour-by-hour simulation, the resulting self-consumption and payback figures are materially different, and generally more favorable, than a simplified household-only analysis would suggest.
For EPC contractors, this means that quoting hybrid inverter capacity, battery sizing, and charger specifications in isolation from one another introduces real risk of underperformance against customer expectations. For investors and developers evaluating residential or small commercial portfolios with EV integration, the verified split between direct self-consumption, EV-directed solar energy, and grid export provides the kind of granular, defensible data needed to model returns with confidence rather than relying on generic assumptions about self-consumption ratios.
As EV adoption accelerates across German, UK, and Turkish residential and commercial markets alike, this type of integrated simulation approach, grounded in verified PVsyst and PV*SOL outputs rather than rule-of-thumb estimates, is becoming a baseline requirement for bankable system design.
