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body_diff: "[{\"diffs\":[[1,\"# PV, Battery & EV Charging Analysis — Complete Study\\\n\\\n**Date:** 2026-06-25 (updated)\\\n**Data basis:** 87 days of smart meter cumulative readings (Mar 30 – Jun 25, 2026)\\\n**Location:** Austria (Styria, near B73)\\\n\\\n---\\\n\\\n## Current System\\\n\\\n| Parameter | Value |\\\n|-----------|-------|\\\n| PV system | 5 kWp roof |\\\n| Inverter | 5 kW |\\\n| Heating | Heat pumps |\\\n| Vehicles | 2 × EV |\\\n| Grid import | ~7,475 kWh/year (€0.36/kWh flat) |\\\n| Grid export | ~1,853 kWh/year (€0.06/kWh feed-in) |\\\n| Estimated PV production | ~5,000 kWh/year |\\\n| Self-consumed PV | ~3,147 kWh/year (63% self-consumption rate) |\\\n| **Total consumption** | **~8,373 kWh/year (22.9 kWh/day)** |\\\n| **Net electricity cost** | **~€2,580/year** |\\\n\\\n---\\\n\\\n## Part 1: Tariff & Battery Analysis (Current 5 kWp System)\\\n\\\n### Dynamic tariff comparison\\\n\\\nDynamic tariff model: `(spot_price + €0.015 margin + €0.150 grid/taxes) × 1.20 VAT`\\\n- Summer avg: ~€0.26/kWh, Winter avg: ~€0.32/kWh\\\n\\\n| Scenario | Annual cost | vs Current |\\\n|----------|--------:|--------:|\\\n| Flat, no battery (CURRENT) | €2,580 | — |\\\n| Dynamic, no battery | €2,097 | **-€483** |\\\n| Dynamic, with battery | €1,839 | -€741 |\\\n\\\n**Verdict: Switch to dynamic tariff immediately (saves €483/yr, zero investment).**\\\n\\\n### Battery on current system\\\n- BYD Battery-Box 10.24 kWh: saves ~€258-312/year\\\n- Payback: 13-20 years depending on tariff\\\n- **Only worth it with subsidy**\\\n\\\n---\\\n\\\n## Part 2: PV Expansion — 10× Scenario (50 kWp)\\\n\\\n### Scenario: Scale current yield ×10, sell via awattar, no EV charger\\\n\\\n| Metric | Current (5 kWp) | 10× PV (~50 kWp) |\\\n|--------|----------------:|-----------------:|\\\n| PV production | 5,000 kWh | **50,000 kWh** |\\\n| Self-consumed | 3,147 kWh (63%) | 6,084 kWh (12%) |\\\n| Grid import | 7,475 kWh | **2,288 kWh** (night only) |\\\n| Grid export | 1,853 kWh | **43,916 kWh** |\\\n| **Net energy position** | **€2,580 cost** | **€2,094 income** |\\\n| **Total benefit vs current** | | **€4,673/year** |\\\n\\\nWith 10× PV + awattar, the household becomes a **net energy producer** — earning ~€2,094/year after covering all daytime demand.\\\n\\\n### Investment & ROI\\\n\\\n| Cost scenario | Investment | Payback | 25-year net profit |\\\n|---|---:|---:|---:|\\\n| Optimistic | €41,000 | **8.8 years** | +€76,000 |\\\n| Mid-range | €52,000 | **11.1 years** | +€65,000 |\\\n| Pessimistic | €64,000 | **13.7 years** | +€53,000 |\\\n\\\n### Export revenue breakdown\\\n\\\nMost export happens at midday when spot prices are lowest:\\\n\\\n| Period | kWh/yr | Revenue | Avg price |\\\n|--------|-------:|--------:|----------:|\\\n| Morning 06-10 | 1,297 | €108 | €0.083 |\\\n| **Midday 10-15** | **27,484** | **€1,563** | **€0.057** |\\\n| Afternoon 15-18 | 13,355 | €864 | €0.065 |\\\n| Evening 18-22 | 1,780 | €191 | €0.107 |\\\n\\\n**Key limitation:** 63% of export revenue comes from midday hours at only €0.057/kWh. This is the bottleneck — you produce the most when prices are worst.\\\n\\\n### Sensitivity to export prices\\\n\\\nEven if awattar export prices collapse, the system remains profitable:\\\n\\\n| Export price | Annual benefit | Payback |\\\n|---|---:|---:|\\\n| Very low (€0.03/kWh avg) | €3,310/yr | 15.7 years |\\\n| Base case (€0.06/kWh avg) | €4,673/yr | 11.1 years |\\\n| High (€0.09/kWh avg) | €6,038/yr | 8.6 years |\\\n\\\nSelf-consumption savings alone (avoiding ~€2,058/yr in import costs) carry most of the value.\\\n\\\n### Stone wall PV — winter game changer\\\n\\\nVertical south-facing 40 kWp wall produces 2.8× more than roof PV in December:\\\n- December: Wall 1,079 kWh vs Roof 386 kWh\\\n- The wall catches the low winter sun directly, solving the seasonal mismatch\\\n\\\n---\\\n\\\n## Part 3: Battery Analysis with 50 kWp + awattar\\\n\\\n### Three battery strategies evaluated\\\n\\\n#### Strategy 1: Self-consumption (charge midday PV, discharge at night) ✅ MARGINAL\\\n\\\n- Charge from PV surplus: opportunity cost €0.057/kWh (lost export)\\\n- Discharge at night: saves €0.277/kWh (avoided import)\\\n- Effective spread after 96% RTE: **€0.20/kWh**\\\n\\\nNightly import to cover: **6.3 kWh/day**\\\n\\\n| Battery size | Cost | Annual value | Payback |\\\n|---|---:|---:|---:|\\\n| 3 kWh | €2,000 | €382 | **5.2 years** |\\\n| 5 kWh | €3,000 | €316 | 9.5 years |\\\n| 7 kWh | €4,000 | €269 | 14.9 years |\\\n| 10 kWh | €5,000 | €198 | 25.3 years |\\\n\\\n**Smaller is better.** A 3-5 kWh battery has the best payback because it charges from the cheapest hours (earliest midday surplus). Optimal size: 5-7 kWh (matches nightly deficit). Beyond 7 kWh, extra capacity is wasted.\\\n\\\n#### Strategy 2: Export arbitrage (store midday, sell at peak) ❌ NOT WORTH IT\\\n\\\n- Midday export price: €0.055/kWh\\\n- Peak export price (18-21): €0.111/kWh\\\n- Spread after RTE: **€0.051/kWh**\\\n\\\n| Season | Midday spot | Peak spot | Spread after RTE |\\\n|--------|----------:|---------:|----------------:|\\\n| Summer | €0.020 | €0.084 | €0.061 |\\\n| Winter | €0.096 | €0.151 | €0.053 |\\\n| Shoulder | €0.049 | €0.097 | €0.046 |\\\n\\\nRevenue per kWh capacity: ~€10/year. Battery cost: ~€400/kWh. **Payback: 40 years.**\\\n\\\nThe Austrian spot price spread between midday and evening (€0.05-0.06/kWh) is too thin for profitable arbitrage.\\\n\\\n#### Strategy 3: Pure grid arbitrage (buy cheap, sell expensive) ❌ IMPOSSIBLE\\\n\\\nGrid fees (€0.15/kWh) on import are NOT refunded on export. Best case:\\\n- Buy at 03:00: €0.258/kWh (incl. fees + VAT)\\\n- Sell at 19:00: €0.120/kWh\\\n- **Spread: -€0.143/kWh (NEGATIVE for ALL hour pairs)**\\\n\\\nEven with full grid fee exemption (Speicherbefreiung): spread only €0.037/kWh → payback 57 years.\\\n\\\n### Battery verdict\\\n\\\n| Question | Answer |\\\n|----------|--------|\\\n| Self-consumption battery? | **Marginally yes.** 5-7 kWh, payback ~10-15 years |\\\n| Export arbitrage? | **No.** Spread €0.05/kWh, payback 40+ years |\\\n| Grid arbitrage? | **No.** Grid fees make all spreads negative |\\\n| Optimal size? | **5-7 kWh** (covers nightly deficit of 6.3 kWh) |\\\n\\\nThe real value spread is self-consumption (€0.22/kWh) vs export arbitrage (€0.05/kWh). The battery should only displace your own night import, never buy-to-re-sell.\\\n\\\n---\\\n\\\n## Part 4: EV Charging Business (Smatrics near B73)\\\n\\\n### Opportunity\\\nAn empty parking lot near the B73 could host public EV charging powered by the large PV system. Instead of exporting at €0.057/kWh, energy sells at EV charging rates (€0.45-0.60/kWh).\\\n\\\n### Economics — the real arbitrage\\\n\\\n```\\\nPV energy cost:     ~€0.08-0.12/kWh (amortized)\\\nEV selling price:   ~€0.45-0.60/kWh\\\nGross margin:       ~€0.33-0.48/kWh  ← 7.5× better spread than battery arbitrage\\\n```\\\n\\\n| Charger type | Hardware cost | Sessions/day | Annual margin | Payback |\\\n|---|---:|---:|---:|---:|\\\n| AC 22 kW | €5,000 | 5-15 | €10,000-30,000 | **0.2-0.5 years** |\\\n| DC 50 kW | €25,000 | 10-25 | €20,000-50,000 | **0.5-1.2 years** |\\\n| DC 150 kW | €45,000 | 15-40 | €30,000-81,000 | **0.6-1.5 years** |\\\n\\\nExcess summer PV (40,000+ kWh) can fuel ~1,000-1,500 EV charges/year on surplus alone.\\\n\\\n### Smatrics engagement plan\\\n\\\n**Status: Should reach out, come prepared.**\\\n\\\nSmatrics handles backend billing, app integration, payment processing, roaming, and customer support. Three possible deal structures:\\\n\\\n1. **You own, Smatrics = backend only** — you keep ~85-90% of revenue\\\n2. **Smatrics turnkey** — they install & operate, you get revenue share or lease\\\n3. **Hybrid** — you provide PV + location, they provide everything else\\\n\\\n**Key questions for Smatrics:**\\\n- Revenue share percentage?\\\n- Dynamic pricing support (cheaper when PV surplus)?\\\n- Hardware recommendations for B73 location?\\\n- Grid connection requirements for DC charging?\\\n- Permitting support (Gewerbe, E-Control, Baueingabe)?\\\n- Maintenance SLA?\\\n- Exclusivity contract terms?\\\n- PV-coupled load management?\\\n\\\n**Also get quotes from:** KEBA (Austrian hardware), evon / The Mobility House (PV-coupled expertise), Energie Steiermark (local utility, may have subsidies)\\\n\\\n**Watch out for:**\\\n- Long-term exclusivity clauses (10-15 years) — avoid on first deal\\\n- Pricing control — ensure YOU can set charging prices\\\n- Seasonal margin compression in winter (grid backup at €0.27/kWh)\\\n- Grid connection upgrade costs for DC fast charging\\\n\\\n---\\\n\\\n## Updated Recommendations\\\n\\\n### Priority 1: Switch to awattar (immediate, free)\\\nSaves ~€483/year with zero investment.\\\n\\\n### Priority 2: Wall PV (30-50 kWp) — 10× scale\\\n- Annual benefit: **€4,673/year** (self-consumption + awattar export)\\\n- Payback: **8.8-13.7 years** depending on installation cost\\\n- 25-year net profit: **€53,000-76,000**\\\n- Turns household from net consumer (€2,580/yr cost) to net producer (€2,094/yr income)\\\n- Unique winter production from vertical south-facing wall\\\n\\\n### Priority 3: EV charger on B73 lot — talk to Smatrics\\\n- Margin: €0.33-0.48/kWh (7.5× better than feed-in, 6× better than battery arbitrage)\\\n- Fast payback: 0.5-1.5 years\\\n- Start with AC charger (low cost, test demand)\\\n- Expand to DC if utilization justifies it\\\n- **This is where the real money is** — not the battery\\\n\\\n### Priority 4: Small battery (optional)\\\n- 5-7 kWh for self-consumption only\\\n- Payback: 10-15 years\\\n- Eliminates remaining €633/yr night import cost\\\n- Lifestyle choice (energy autonomy) more than financial optimization\\\n- **DO NOT oversize** — extra capacity has 40+ year payback\\\n\\\n### Recommended phasing\\\n1. **Now:** Switch to awattar (free, saves €483/yr)\\\n2. **Phase 1:** Talk to Smatrics + wall PV 30 kWp (~€35,000)\\\n3. **Phase 2:** AC charger on B73 lot (~€5,000)\\\n4. **Phase 3:** Additional roof PV 5-10 kWp (~€7,000-13,000)\\\n5. **Phase 4:** DC fast charger if AC utilization good (~€25,000-45,000)\\\n6. **Optional:** 5 kWh battery for night autonomy (~€3,000)\\\n\\\n---\\\n\\\n## Methodology & Assumptions\\\n\\\n### Data source\\\n- Smart meter cumulative totals from Home Assistant\\\n- 45,709 import + 4,474 export data points, 87 days (Mar 30 – Jun 25, 2026)\\\n- Hourly consumption profile derived from P90 import percentile (cloudy-day demand)\\\n- PV production calibrated to 5,000 kWh/year (typical 5 kWp Austria, ~1,000 kWh/kWp)\\\n- PV = 0 for nighttime hours (22:00-06:00)\\\n\\\n### Price model (awattar)\\\n- Import: `(spot + €0.015 margin + €0.150 grid/taxes) × 1.20 VAT`\\\n- Export: `spot - €0.005 deduction`\\\n- Seasonal spot averages: summer €0.07, shoulder €0.09, winter €0.12\\\n- Hourly profiles from EPEX/EXAA patterns\\\n\\\n### Battery simulation (corrected)\\\n- Daily cycle: charge midday surplus (hours 9-18), discharge evening+night (hours 19-8)\\\n- Charge order: hours 9→23→0→8 (solar-day sequence)\\\n- 96% round-trip efficiency (sqrt applied per direction)\\\n- Nightly import: 6.33 kWh/day (hours 0-8, 20-23)\\\n\\\n### PV expansion model\\\n- 10× scaling of current hourly PV profile\\\n- Self-consumption: all daytime demand covered (PV >> demand)\\\n- Remaining import: nighttime only (6.3 kWh/day = 2,288 kWh/year)\\\n- Export: 43,916 kWh/year, mostly midday (63% during hours 10-15)\\\n\\\n### Limitations\\\n- Winter data is synthetic (modeled from spring/summer patterns)\\\n- Actual awattar spot prices vary — verify with historical data\\\n- EV charger utilization depends on actual B73 traffic (unverified)\\\n- Wall PV yield depends on exact orientation and shading\\\n- Regulatory costs not fully modeled (permits, grid upgrades, Gewerbe)\\\n- No PV degradation modeled (typically 0.5%/year)\\\n- Battery costs assumed at ~€400-500/kWh (BYD LVS pricing)\\\n- Investment estimates are rough (±20%)\"]],\"start1\":0,\"start2\":0,\"length1\":0,\"length2\":11058}]"
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updated_time: 2026-06-25T07:57:26.876Z
created_time: 2026-06-25T07:57:26.876Z
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