Electric vehicle batteries: V2G technologies and storage

Introduction: The electric vehicle battery, an asset to protect

Electric vehicles represent a significant investment (€40,000 to €80,000), with the battery accounting for 30 to 40% of the total value. With capacities ranging from 40 kWh to over 100 kWh, these batteries are generating increasing interest for home energy storage via V2G, V2H, and V2L technologies.

But beware: marketing promises about the durability of vehicle batteries and their use in energy storage mask a much less rosy reality. Actual degradation is two to three times faster than manufacturers claim , and intensive V2G use can void your warranty or cost you €12,000 to €20,000 for out-of-warranty replacements.

"At Wattuneed, our recommendation is clear: for home energy storage, opt for a dedicated LFP stationary battery (like our 15 kWh model at €2400 including VAT) rather than prematurely wearing out your electric vehicle's battery, a valuable and expensive asset to replace."

In this guide, we reveal the truth about different battery chemistries , real degradation data (far from marketing promises), the pitfalls of manufacturer warranties , and why a stationary solar battery remains the safest and most cost-effective choice for your photovoltaic installation.

🔴 Reality vs. Marketing: The true degradation of electric vehicle batteries

What manufacturers say (marketing)

• "Our batteries retain 90% of their capacity after 200,000 km"
• "Average degradation of only 1 to 2% per year"
• "8-year/160,000 km warranty with a minimum of 70% capacity"
• "V2G usage does not significantly impact lifespan"

What the actual data shows (2024-2025)

Genuine customer testimonial: "My Tesla Model X with 69,000 km has only 89% usable capacity left, a loss of 11%. I can clearly see its wear and tear in charging speed and actual range." – Tesla owner for 2 vehicles

Sources: Reddit r/TeslaLounge, Tesla Motors Club, Geotab 2024-2025 studies, Tessie App user feedback

The 3-phase degradation curve

1. Phase 1 (0-50,000 km): Rapid degradation of 5-8% – this is the most critical period
2. Phase 2 (50,000-150,000 km): Stabilization at 1-2% per year
3. Phase 3 (>150,000 km): Accelerated degradation, risk of module failure

Major implication: A vehicle with 70,000 km has already lost 8-12% of its capacity. Using it daily for V2G will accelerate this degradation irreversibly.

The different battery chemistries: real advantages and disadvantages

1. NMC (Nickel-Manganese-Cobalt) Batteries

NMC batteries equip the majority of European electric vehicles: Volkswagen ID.3/4, Hyundai Ioniq 5, Kia EV6, Renault Mégane E-Tech, Peugeot e-208, etc.

Benefits :

• High energy density: 200-240 Wh/kg → range 400-600 km
• Discharge power: excellent acceleration
• Fast charging: accepts up to 250 kW DC

MAJOR drawbacks (often hidden):

• Actual lifespan: 1200-1800 complete cycles (not the advertised 2000)
• Rapid degradation: 10-12% loss at 100,000 km under standard use
• Sensitivity to full charges: recommendation to limit to 80% → you already lose 20% of usable battery life
• Replacement cost: €12,000 to €18,000 excluding warranty
• Risky V2G usage: accelerates degradation by 30-50% according to studies

2. LFP batteries (Lithium-Iron-Phosphate or LiFePO4)

LFP batteries are used in: Tesla Model 3 Standard Range, BYD, Dacia Spring, some MG models and Chinese vehicles.

Benefits :

• Longer lifespan: 2500-4000 actual cycles (compared to the advertised 3000-5000)
• Cost 30-40% lower
• Daily 100% load: more stable chemistry
• Enhanced safety: minimal risk of thermal runaway
• Better V2G tolerance (but with some degradation nonetheless)

Disadvantages:

• Lower energy density: 150-180 Wh/kg → 20% less range
• Cooling performance: significant loss of autonomy below 0°C
• Weight increased: +15-20% at equal capacity
• Actual degradation: 5-8% at 100,000 km (not the advertised 3-4%)

3. NCA (Nickel-Cobalt-Aluminum) Batteries

Primarily Tesla Model S and Model X (older versions up to 2022).

Features :

• Maximum energy density: up to 250 Wh/kg
• ACTUAL lifespan: 1000-1500 cycles (the worst of the 3 chemistries)
• Rapid degradation: 10-15% at 100,000 km
• Replacement cost: €15,000 to €22,000 (Model S/X)
• ⚠️ AVOID for any V2G use

⚠️ V2G/V2H Technologies: Hidden Dangers and Safe Alternatives

V2L (Vehicle-to-Load): The only reasonable use

The V2L allows you to power portable devices via a 230V socket (2.3 to 3.6 kW).

Reasonable use: Camping, construction sites, occasional repairs (a few hours per month)

Battery impact: Negligible if used < 10 times/year

Equipped vehicles: Hyundai Ioniq 5/6, Kia EV6/EV9, Dacia Spring, Renault 5 E-Tech, MG4/MG5, Peugeot e-3008

V2H (Vehicle-to-Home): Appealing but financially risky

The concept: Use the vehicle's battery to power your home (7-10 kW)

⚠️ Real dangers:

• High investment: €4,000-€6,000 (bidirectional hybrid inverter + V2H charger + installation)
• Accelerated wear: Daily use (5 kWh/day) = 180 additional cycles/year
• Guaranteed risk: Many manufacturers exclude "commercial" or "non-standard" use.
• Hidden cost: Out-of-warranty battery replacement = €12,000-€20,000
• Reduced flexibility: Your vehicle must remain plugged in → loss of mobility

V2G (Vehicle-to-Grid): The Marketing Trap

The concept: Sell electricity back to the grid and generate passive income

🔴 The economic reality:

Realistic calculation:

• V2G income over 8 years: €1,200-€2,400
• Value of lost battery: €3,600-€7,200
• Net loss: -€2,400 to -€4,800

"Using a €40,000-€60,000 electric car battery to save €200/year on V2G is like using a €50,000 professional tool to save €200 per year. It's economically irrational." – Wattuneed Expert

✅ The smart alternative: Dedicated LFP stationary battery

Why is a stationary battery superior to V2G?

Concrete example: Belgian house with solar panels

Profile: House consuming 20 kWh/day, 6 kWp installation (production 25 kWh/day in summer)

V2G solution (60 kWh NMC vehicle):

• Investment: €50,000 (vehicle) + €5,000 (equipment) = €55,000
• Daily usage: 10 kWh (home storage) = 180 cycles/year
• Degradation over 8 years: 12% × 60 kWh = 7.2 kWh lost → lost value: €4,320 (at €600/kWh)
• Electricity savings: €400/year × 8 years = €3,200
• Result: -€1,120 + loss of mobility

Wattuneed solution (stationary 15 kWh LFP battery):

• Investment: €2,400 including VAT ( Delong 15kWh Lithium battery )
• Daily usage: 10 kWh = 240 cycles/year
• Degradation over 8 years: < 5% × 15 kWh = 0.75 kWh → negligible loss
• Electricity savings: €400/year × 8 years = €3,200
• Result: +€800 + total flexibility + vehicle preserved

Discover our LFP stationary batteries

Our range of LFP stationary batteries

• Pylontech US3000C battery (3.5 kWh): €1,200 incl. VAT – modular, stackable
• Pylontech US5000 battery (4.8 kWh): €1,650 including VAT – market reference
• Sofar Solar 5.12 kWh battery: €1,890 incl. VAT – compatible with all inverters
• Delong 15 kWh battery: €2,400 including VAT – best capacity/price ratio
• Modular batteries up to 30 kWh

All our batteries: 10-year warranty, 6000+ cycles, LFP CALB/EVE prismatic cells, CE certified

🚨 Manufacturer warranties: Hidden clauses and exclusions V2G

What manufacturers don't say clearly

Standard warranty: 8 years or 160,000 km with a minimum of 70% capacity maintained

⚠️ Translation: They anticipate and allow for 30% loss ! Your battery can lose 30% without them intervening.

Common exclusions (read in the small print)

• "Commercial or non-compliant use" → V2G can be considered as such
• "Excessive charge/discharge" → daily V2G cycles = possible exclusion
• "Use contrary to recommendations" → legal ambiguity
• "Modification of the electrical system" → V2H installation = risk
• Frequent fast charging → may void the warranty with some manufacturers

Table of actual warranties by manufacturer

⚠️ Crucial advice: Before making any V2G investment, ask your dealer in writing if daily V2H/V2G use is covered by the warranty. Most will refuse to do so.

Concrete examples: Vehicle capacities and replacement costs

Popular vehicles in Belgium/France (2025)

Calculating the actual cost per kWh stored

Vehicle battery (example VW ID.3, 58 kWh NMC):

• Vehicle cost: €43,000
• Estimated battery cost (35% of the vehicle): €15,000
• Actual guaranteed cycles: 1,500 cycles
• Cost per kWh stored: €15,000 / (58 kWh × 1,500 cycles) = €0.17/kWh
• With daily V2G usage (5 kWh/day): 8 kWh battery wear → €1.36 per day of wear

Wattuneed stationary battery (15 kWh LFP):

• Battery cost: €2,400 including VAT
• Guaranteed cycles: 6,000 cycles
• Cost per kWh stored: €2,400 / (15 kWh × 6,000 cycles) = €0.027/kWh
• With daily storage (10 kWh/day): €0.27 per day of wear and tear

Conclusion: A vehicle battery costs 5 times more per kWh stored than a dedicated LFP stationary battery!

Calculate your storage needs

Optimal coupling: Solar panels + Stationary battery + EV for mobility

The winning strategy recommended by Wattuneed

Optimal configuration:

1. Photovoltaic panels : 6-10 kWp depending on your consumption
2. Hybrid inverter : Sofar Solar, Deye, Fronius (5-10 kW)
3. LFP stationary battery : 10-20 kWh depending on needs
4. Electric vehicle : used solely for mobility, charged with surplus solar energy
5. Occasional V2L use : camping, breakdown assistance (< 10 times/year)

Typical scenario (Belgian house, 6 kWp solar panels)

Data :

• Annual solar production: 5,500 kWh
• Household energy consumption: 6,500 kWh/year
• Surplus solar energy (without battery): 2,000 kWh/year sold back to the grid at €0.05/kWh = €100
• Vehicle energy requirements: 2,500 kWh/year (15,000 km)

With a Wattuneed 15 kWh stationary battery:

• Home self-consumption: 85% (instead of 40%)
• Electricity savings: 2,000 kWh × €0.30/kWh = €600/year
• Vehicle charging with surplus solar energy: 1800 kWh/year free (savings of €540/year)
• Total savings: €1,140/year
• Battery return on investment (€2,400): 2.1 years

Required equipment:

• Hybrid inverter: €1,800-€3,500 depending on power
• LFP 15 kWh battery: €2,400 incl. tax
• Installation: €800-1,200
• Total: €5,000-€7,100
• Depreciation: 4-6 years

Request a free personalized study

⚠️ Final precautions and recommendations

What you absolutely must avoid

• ❌ Using your new vehicle daily in V2G mode → guaranteed premature wear
• ❌ Trusting marketing promises about battery durability
• ❌ Investing €5,000 in V2H equipment without a written manufacturer's warranty
• ❌ Always charging at a supercharger → accelerates degradation
• ❌ Leave the battery at 100% or 0% for several days
• ❌ Ignoring warranty exclusions in the fine print

What we recommend

• ✅ Invest in a dedicated LFP stationary battery (€2,400 for 15 kWh)
• ✅ Use your EV only for mobility → preserve the asset
• ✅ Charge your EV with excess solar energy via the hybrid inverter
• ✅ Occasional V2L use only (< 10 times/year, a few hours)
• ✅ Maintain a daily charge of 20-80% for NMC batteries
• ✅ Prefer slow charging at home (7-11 kW AC)
• ✅ Monitor degradation with apps like Tessie, TeslaMate

Wattuneed guarantees on our stationary batteries

• ✅ Firm 10-year warranty with no vague exclusion clauses
• ✅ 6,000+ certified cycles (manufacturer data verified)
• ✅ LFP prismatic CALB/EVE cells (premium quality)
• ✅ Compatible with all hybrid inverters (Sofar, Deye, Fronius, Victron, etc.)
• ✅ Wattuneed technical support : support.wattuneed.com
• ✅ Installation by certified professionals (on request)
• ✅ Replacement of individual modules in case of failure (not a complete replacement)

Frequently Asked Questions (FAQ)

1. My builder is offering me an "official" V2G service, is that safe?

Answer: Ask in writing if the battery warranty explicitly covers daily V2G use and additional cycles. Check the financial balance: does the V2G revenue (€200-€400/year) offset the accelerated wear of your battery (value: €12,000-€20,000)? In 90% of cases, the answer is no.

2. I already have an electric vehicle, can I still invest in a stationary battery?

Answer: Yes, and it's even recommended! This allows you to preserve your vehicle for mobility while optimizing your 24/7 solar self-consumption. The stationary battery will always be present, unlike your vehicle which may be in motion.

3. What stationary battery capacity do I need for my home?

Answer: Simple rule: 50-70% of your consumption should be at night . For a house consuming 20 kWh/day (14 kWh at night), aim for 7-10 kWh of storage. Use our free sizing calculator .

4. Are LFP batteries really more durable than NMC batteries?

Answer: Yes, real-world data confirms 2,500-4,000 cycles for LFP batteries versus 1,200-1,800 for NMC batteries. Our Wattuneed batteries are certified for 6,000+ cycles with a 10-year warranty, which is 2-3 times more than vehicle batteries.

5. What happens if my vehicle battery fails out of warranty?

Answer: Complete replacement costs between €8,000 and €22,000 depending on the model. This is why it's crucial to preserve this asset and avoid premature wear with intensive V2G use. A stationary battery costing €2,400 can be replaced without significant financial hardship.

6. Can I combine a stationary battery + smart EV charging?

Answer: Yes, this is the optimal configuration! Your hybrid inverter manages priorities: (1) home consumption, (2) charging stationary battery, (3) charging vehicle with excess power. Everything is automated via the monitoring app.

Conclusion: Protect your investment, choose the dedicated solution

Electric vehicles represent a major investment (€40,000 to €80,000), with the battery accounting for 30 to 40% of that value. Real-world degradation data shows that vehicle batteries wear out two to three times faster than marketing claims suggest , with an 8-15% loss over 100,000 km in standard use.

Using this expensive battery for home energy storage via V2G/V2H is economically risky:

• Cost per kWh stored: €0.17/kWh (vehicle battery) vs €0.027/kWh (LFP stationary battery)
• Risk of exclusion from manufacturer's warranty
• Replacement cost outside of warranty: €12,000-€20,000
• Loss of flexibility and mobility

The smart solution recommended by Wattuneed:

1. Dedicated stationary LFP battery (15 kWh at €2,400 including VAT) for solar storage
2. Hybrid inverter to control your entire installation
3. Electric vehicle preserved for mobility, charged with surplus solar energy
4. Occasional use by two-wheeled vehicles only (camping, breakdown assistance).

Advantages of this approach:

• ✅ Controlled investment: €2,400 vs. €50,000 (vehicle)
• ✅ Firm 10-year warranty, 6,000+ cycles
• ✅ Total independence: battery available 24/7
• ✅ Cost per cycle 5x lower
• ✅ Vehicle preserved for mobility
• ✅ Optimal solar self-consumption: 80-90%
• ✅ Depreciation: 2-4 years

At Wattuneed, we believe in transparency and protecting your investments. Don't be swayed by V2G marketing promises that conceal hidden costs and real risks. Choose a dedicated, reliable, and guaranteed solution that respects both your electric vehicle and your budget.

Discover our LFP stationary batteries. Request a free study.

Wattuneed SPRL – Your Belgian partner for photovoltaic and energy storage solutions. Transparency, honest advice, and personalized support for your energy transition.
📞 Contact: support.wattuneed.com | 🔧 Toolbox: Calculators and sizing tools | 📚 Blog: Photovoltaic Guide
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