Summary of "Heimspeicher vor dem Aus? Lohnt sich ein Kauf überhaupt noch?"

Brief overview

The video examines Vehicle-to-Grid (V2G) and Vehicle-to-Home (V2H), covering technical principles, economics, battery impact, hardware requirements and real-world program examples — and evaluates whether buying into these systems makes sense today.

Key technological concepts

V2G: bidirectional charging where an EV can feed energy back to the public grid (traded on power markets or held as reserve capacity).
V2H: using an EV battery as additional home storage (for example, to store PV surplus and supply the house in the evening).
Power markets: reserve capacity, day‑ahead and intraday markets determine when storage is called on or traded; market rules can limit how long or how deep batteries are discharged.

Round‑trip efficiency: typical losses ≈20% (i.e., feed 10 kWh → need ≈12 kWh back), so compensation/pricing must cover losses.

Real‑world program example (BMW + E.ON)

Offer: plug a BMW i3 into a BMW wallbox; E.ON trades the battery on the exchange and pays a standby fee (advertised €0.24/hour while plugged in).
Cap: €60/month (≈250 paid hours).
Hardware constraint: current program requires BMW i3 and BMW DC wallbox (~€2,095).
Example cost: purchase + wallbox example ≈ €71,000.
Contract constraints: program comes with an E.ON green fixed tariff and monthly fee; dynamic tariffs are generally not allowed — this can materially affect economics.

Battery usage, markets and protections

Market mechanics:
- Batteries are often offered as reserve capacity and are only called upon if needed.
- Trading typically limits discharge to short periods (experts: max ~2 hours in one direction).
State of charge (SOC) protections: traders/operators reportedly keep at least ~50% SOC to ensure the car remains drive‑ready.
Transparency issue: V2G is often a “black box” for users — limited visibility on when and how the battery is used once plugged in.

Battery degradation analysis

Summary of experts and findings:

Prof. Dirk Uwe Sauer (RWTH Aachen)
- Full daily equivalent cycles (365/year) are unrealistic under current market rules.
- Discharge depth per event is limited (example: ~20% with 11 kW).
Tom Böttcher (battery expert/YouTuber)
- Calendar aging usually dominates EV battery wear.
- Controlled, gentle bidirectional cycles (small depth, slow rates; e.g., a 30–60% window) cause minimal extra degradation.
Empirical finding
- A cited 2025 study found ~1.8–2.5% additional degradation over 10 years from regular bidirectional use (when done with certified equipment and controlled cycles).

Practical takeaway: properly controlled V2G/V2H has relatively low impact on battery life; most manufacturers currently keep warranties intact under specified conditions.

V2H economics and scenarios

Key determinants:

Existing home battery size
PV system size
Household consumption profile
Charging power
Grid/network fees (especially fixed components)

Typical scenarios:

No home storage + PV: V2H can be very beneficial — the EV replaces a basement battery for evening demand.
Small home battery (~8 kWh): adding an EV often gives little extra benefit because night demand is already met.
Very small PV (balcony panels): V2H is generally not cost‑effective; household base load consumes most generation and round‑trip losses erase gains.

Arbitrage (buy low, use when prices are high):

Creator’s calculator example: small household with 20 kWh usable EV storage → ~€69/year savings without special grid fee treatment.
Three levers that matter:
1. Household consumption — more consumption raises absolute savings.
2. Charging power — “speed is money”; need sufficient charging power (~3 kW+ to be useful; 11 kW typical).
3. Battery size — bigger is not always better if the household can’t deplete it during expensive periods.

Network fees effect:

Fixed grid/network charges greatly reduce arbitrage margins.
Example (Germany, Paragraph 14a Module 3): if available, it can drop fees during charging windows and substantially increase potential savings (example moving from ~€69 to >€200/year).
Availability of Paragraph 14a varies by grid operator; only a few households have it active today.

Hardware, cost and compatibility

Wallbox types:
- AC bidirectional wallbox (11 kW): cheaper (≈€800–€1,500) because DC/AC conversion happens inside the car.
- DC wallbox: more expensive (BMW wallbox example €2,095) because conversion electronics are in the wallbox.
Car compatibility: only a few EV models currently support bidirectional charging. You must buy a compatible car and compatible wallbox.
Contract limitations: some provider programs bundle fixed‑rate electricity contracts and may restrict choice of dynamic tariffs.

Practical advice / checklist before pursuing V2G/V2H

Does your car support bidirectional charging?
Which wallbox types are compatible and what do they cost?
Do you already have home storage? What are your PV size and household consumption profile?
What are your local network charges and is Paragraph 14a available from your grid operator?
Ask providers about SOC guarantees and transparency of usage (can you see when/what your battery is used for?).
Consider long‑term degradation vs. expected earnings and check manufacturer warranty conditions.

Tools mentioned:

Creator’s free arbitrage calculator (no registration) to estimate V2H savings.
PV modelling tool linked in the video.
PV Magazine and Battery Charts for market and battery data.

Conclusions

V2G and V2H are technically feasible and can be financially attractive in certain cases, but outcomes are highly case‑specific.
Major constraints: hardware availability and cost, car compatibility, grid fees/regulations, limited market windows, and current lack of transparency.
Properly controlled bidirectional use appears to cause only modest additional battery degradation.
Market and product evolution and broader compatibility will be decisive over the next few years.

Main speakers / sources referenced

Video presenter (host; developer of the arbitrage/PV tools; sponsor promo code “Akkudoktor”).
Prof. Dr. Dirk Uwe Sauer — RWTH Aachen University; co‑founder of Battery Charts.
Tom Böttcher — battery expert and YouTuber.
BMW & E.ON — commercial V2G program example.
Additional sources: Battery Charts, PV Magazine, an unnamed 2025 study on bidirectional cycling, and German regulatory detail Paragraph 14a Module 3.