PV + Storage + EV Calculator
Autarchy, Self-Consumption & Payback — a fast, understandable scenario calculation (no external libraries).
Values Tip: First PV + Consumption, then Storage & Smart-Charging
Result Live Charts + Payback
FAQ
What does "Autarchy" mean specifically?
Autarchy is the share of your total electricity demand (Household + EV charging at home) that you can cover via PV and storage. 70% autarchy means: 30% still comes from the grid on annual average.
Why isn't "Self-Consumption" automatically high with large PV?
The larger the PV in relation to consumption, the more surplus is generated that cannot be used in time. Then the self-consumption ratio drops, even though the autarchy level may rise.
How does Smart-Charging work for the EV?
Smart-Charging shifts charging into times with PV generation (e.g., noon). This increases the direct PV share for the EV and improves self-consumption as well as autarchy, often cheaper than "even more storage".
Why is this a monthly simulation and not minute-by-minute?
Monthly values are fast, stable, and easy to understand. For exact planning (quarter-hour load profiles, shadows, tariff details) you need specialized simulations, but for scenario comparisons, this model is usually sufficient.
Which inputs are most important for realistic results?
Household consumption from your annual bill, realistic PV yield (Region, Roof), electricity price, feed-in tariff, and your EV charging behavior (home-share + smart-charging).
How is the Payback calculated?
The calculator simulates annual net cash flows (Savings + Feed-in − O&M) over 25 years, incl. PV degradation and optional price increases. Payback is the year in which the cumulative cash flow first becomes ≥ 0.
What does "Uplift via Storage" mean?
This is the difference "with storage" vs. "without storage" in Autarchy and annual net benefit. This way you see immediately if the storage actually brings value in your scenario.
PV + Battery + EV Calculator: Autarchy, Cash Flow & 25-Year Payback
This calculator models the complete interaction between a rooftop PV system, a home battery, and an electric vehicle — the three-component energy system that is becoming the standard setup for German homeowners seeking maximum energy independence. It outputs autarchy rate, self-consumption, annual cash flow, and a full 25-year economic projection including payback period.
Autarchy Rate
Percentage of total household + EV energy demand covered by own PV generation (directly consumed + from battery). System benchmark: PV only ~50–60%; PV + battery ~75–85%; PV + battery + smart EV charging ~85–95%.
Self-Consumption Rate
Percentage of generated PV electricity used within the system (household + battery + EV) vs. fed into the grid. Higher = better economics, as self-consumed kWh avoids grid purchase at ~33 ct; fed-in earns only ~8 ct.
EV Charging Analysis
Annual EV energy demand (km/year ÷ EV consumption in kWh/100km), split between PV-covered charging vs. grid charging. Charging from own PV saves ~10 ct/km vs. public charging at ~45 ct/kWh.
Annual Cash Flow
Electricity cost savings + EV charging savings + feed-in revenue minus system financing cost (if financed). Shows net annual benefit per year for 25 years, adjusting for electricity price increases and PV panel degradation.
Payback Period
Year when cumulative cash flows equal total system investment. Displayed on the cash flow chart as a highlighted crossover point. With EV: typically 1–3 years faster than PV + battery without EV.
25-Year Cash Flow Chart
Annual and cumulative net cash flow for 25 years, accounting for: electricity price escalation (default 3%/year), PV degradation (0.4%/year), and optional battery replacement at year 12–15.
Recommended System Sizing by Household Profile
| Household profile | PV system | Battery | Expected autarchy | Est. total cost |
|---|---|---|---|---|
| 2-person, no EV (3,500 kWh/year) | 6–8 kWp | 7–10 kWh | 75–82% | €20,000–28,000 |
| 4-person, no EV (4,500 kWh/year) | 8–10 kWp | 10–12 kWh | 72–80% | €25,000–35,000 |
| 4-person + 1 EV (15,000 km/year) | 10–12 kWp | 10–15 kWh | 80–88% | €30,000–42,000 |
| 4-person + heat pump + EV | 14–18 kWp | 15–20 kWh | 82–90% | €40,000–58,000 |
| 5+ person, high consumption, 2 EVs | 18–25 kWp | 20–30 kWh | 85–93% | €55,000–80,000 |
Battery sizing tip: Sizing the battery to store ~1.0–1.5× your average daily household consumption (excluding EV) is optimal. Larger batteries have diminishing returns — the additional capacity sits unused on sunny summer days and barely bridges winter nights. EV charging provides an additional large buffer if the car is charged during the day from PV surplus.
System Configurations: Economic Comparison Over 25 Years
Example: 4-person household in Bavaria, 4,500 kWh/year base consumption, 10 kWp PV, electricity price €0.34/kWh, 3%/year price escalation. EV: 15,000 km/year, 18 kWh/100km.
| Configuration | Total investment | Autarchy | Payback period | 25-year net benefit |
|---|---|---|---|---|
| PV only (10 kWp) | ~€14,000 | ~58% | ~10–11 years | ~€38,000 |
| PV + 10 kWh battery | ~€24,000 | ~78% | ~12–14 years | ~€44,000 |
| PV + battery + EV charging | ~€24,000 | ~84% | ~10–12 years | ~€58,000 |
| PV + battery + EV + heat pump | ~€38,000 | ~87% | ~13–16 years | ~€72,000 |
Key insight: Adding an EV to a PV + battery system often pays back faster than the battery alone — because EV charging from own PV replaces expensive public charging (~€0.45/kWh or petrol) with nearly free energy, creating very high effective savings per kWh consumed.
Frequently Asked Questions
How does bidirectional EV charging (V2H / V2G) affect the calculation?
Vehicle-to-Home (V2H) and Vehicle-to-Grid (V2G) allow the EV battery to discharge back into the home (V2H) or the grid (V2G), effectively using the car as an additional ~40–80 kWh battery. This can dramatically increase autarchy — particularly in winter when PV generation is low — by drawing on the car's battery at night after daytime PV charging. V2H-capable vehicles (as of 2026: Nissan Leaf Gen 2, Hyundai Ioniq 5/6, Kia EV6, select Volkswagen ID models with bidirectional charging hardware) require a compatible V2H home unit (~€3,000–5,000 additional investment). Enable the "Bidirectional charging" toggle in the Advanced settings to model V2H economics — it typically adds 5–10 percentage points of autarchy and improves payback by 1–2 years.
What happens to the calculation after the battery needs replacement?
Home batteries have a guaranteed cycle life of typically 4,000–6,000 full cycles, equivalent to approximately 12–15 years of daily use. After this point, battery capacity drops to 70–80% of original — still functional but with reduced performance. The calculator includes a battery replacement event at year 12 or 15 (configurable) with an estimated replacement cost of €300–500/kWh (prices are declining ~8–10%/year). This replacement cost is deducted from the cash flow in that year. In practice, many users choose to upgrade to a larger battery at replacement time, which is modeled by the "Battery upgrade at replacement" option.
Does the calculator account for the German Balkonkraftwerk (plug-in solar) separately?
No — the calculator models full rooftop PV installations from 3 kWp upward. Balkonkraftwerke (plug-in solar, up to 2 kWp registered as of 2024 in Germany, or up to 800W without registration) are a separate product category with different economics and a much simpler installation. For balcony solar, the relevant calculation is simply: annual kWh produced × (grid electricity price − any curtailment loss) to estimate savings. A separate Balkonkraftwerk calculator on this site covers that scenario. The rooftop PV + battery + EV calculator is designed for full installations where professional installation and grid connection are involved.
How accurate is the 25-year cash flow projection?
The projection is directionally accurate but relies on assumptions that introduce uncertainty over 25 years. The most sensitive assumptions are: (1) electricity price escalation — the calculator defaults to 3%/year based on German historical average (2000–2025), but actual rates could be 1–5%. (2) Feed-in tariff — locked in for 20 years from commissioning, so this is actually one of the more predictable inputs. (3) PV panel degradation — well-established at 0.3–0.5%/year for quality panels. (4) EV charging behavior — varies significantly by season and driving pattern. The sensitivity analysis tab in the Advanced section lets you run scenarios with low (1.5%/year), base (3%/year), and high (5%/year) electricity price escalation to see the range of possible outcomes.
Embed this Calculator on Your Website
You can integrate this calculator for free into your own website. Get the embed code on our overview page.