Solar Wallbox in Germany: Charging Your EV From PV Surplus

Every kilowatt-hour of your own rooftop solar you pour into the car instead of selling to the grid is worth about 29 cents in Germany right now. That single number — not the panels, not the wallbox brand — is why PV surplus charging (Überschussladen) is one of the best returns a solar owner can get. Here is the real economics, the wallboxes that can do it, and the honest catch.

TL;DR — solar EV charging in Germany

Self-consumed solar effectively costs you the foregone feed-in tariff — 7.78 ct/kWh in 2026 — versus a ~37 ct/kWh grid average, so each surplus kWh into the car saves roughly 29 ct.
Surplus charging needs a wallbox that modulates power to your solar export: minimum 1.4 kW single-phase (6 A), or 4.2 kW three-phase.
Capable 2026 boxes include go-e Gemini, myenergi Zappi, KEBA PV Edition, Fronius Wattpilot, and openWB — each needs an energy meter or EMS.
A realistic annual saving is ~€200–€350 for a typical driver; solar covers around 46% of charging without a battery.
The catch is seasonality: solar share collapses in winter and needs daytime charging or a home battery.

~29 ct/kWhwhat each kWh of surplus solar charged into your EV saves versus the German grid average (2026)

The number that makes solar charging worth it

The mistake most explanations make is pricing solar by what it cost to generate. Once your panels are paid for and on the roof, that is a sunk cost. The number that actually decides each kilowatt-hour is the opportunity cost: what you give up by not exporting it.

In 2026, a new small rooftop system (up to 10 kWp) earns a feed-in tariff of 7.78 ct/kWh for surplus export, set by the Bundesnetzagentur for systems commissioned between 1 February and 31 July 2026. Meanwhile, the average German household pays 37.0 ct/kWh for grid electricity (BDEW, reference April 2026). So when you send a kWh of solar to the car instead of the grid, you forgo 7.78 ct of income but avoid 37 ct of cost — a net gain of about 29 ct per kWh.

Note

That ~29 ct is the honest figure, and it is opportunity cost, not generation cost. Solar's levelised cost for a small roof is roughly 6–12 ct/kWh (Fraunhofer ISE, 2024) — but that money is already spent. For an owner deciding where each kWh goes today, the foregone 7.78 ct feed-in is the number that counts.

How PV surplus charging (Überschussladen) works

Surplus charging keeps the car drinking only what the roof is exporting. An energy meter or current sensor at the grid connection watches your live feed-in; the wallbox then modulates its charging current up and down to match, so you draw from solar rather than the grid.

There is a physical floor. A single-phase wallbox can throttle down to 6 A ≈ 1.4 kW; a three-phase one needs 3 × 6 A ≈ 4.2 kW to run at all. The best systems do automatic one-/three-phase switching, so charging can start from as little as 1.4 kW of surplus on a cloudy afternoon instead of waiting for a full 4.2 kW.

Which wallboxes support surplus charging

Not every wallbox can do this, and most need an extra piece of hardware — an energy meter or an energy-management system (EMS). The current German-market options:

Wallbox	Extra hardware needed	Notes
go-e Charger Gemini flex 2.0	go-e Controller (meter) or evcc/openWB	Open API, flexible
myenergi Zappi	only a harvi CT sensor	Built-in phase switching from 1.4 kW
KEBA P30 PV Edition	energy meter + phase-switching device	Solid all-rounder
Fronius Wattpilot	native with Fronius PV	Auto 1-/3-phase from 1.4 kW
openWB series2 / Pro	EMS built in	Open-source, controls many boxes
Easee Home	—	Cloud-dependent; not recommended for surplus

If you are still choosing hardware, the full home-wallbox comparison weighs these boxes on price, features, and smart-charging support.

What you actually save: a worked example

Concrete numbers beat percentages, so here is a conservative case with every assumption on the table. Take a driver covering 13,500 km a year at 19 kWh/100 km including charging losses (mid-range for the ADAC Ecotest fleet) — about 2,565 kWh of charging a year. Field data from HTW Berlin puts the solar share at roughly 46% for a 5–10 kW system without a battery.

Charging approach	Solar kWh	Grid kWh	Annual cost
100% grid @ 37 ct	0	2,565	€949
Surplus solar + grid mix	~1,180 @ 7.78 ct	~1,385 @ 37 ct	€604
Difference	—	—	≈ €345 saved/yr

When I ran this math against my own per-100km home-charging figures, the saving held up — but it is sensitive to your grid price. Charge the non-solar share on a cheaper ~28 ct/kWh EV tariff and the all-grid baseline drops to about €718, so the solar saving narrows to roughly €240 a year. Real, worthwhile, but not the "free driving" some marketing implies.

The catch: seasonality and daytime charging

The averages hide a seasonal swing that matters. Solar yield in December is a fraction of June, so the 46% annual solar share is mostly earned in summer; winter charging is largely grid. And surplus charging only works when the car is plugged in during daylight — a commuter who charges at 8 pm captures very little sun unless a home battery bridges the gap.

Warning

Do not size your expectations on a sunny July afternoon. Without a battery, a night-charging commuter may see far less than the 46% headline solar share, and three-phase cars that cannot phase-switch need a full 4.2 kW of surplus before they will start at all. Match the setup to when you actually charge, not just how much you drive.

Do you need a home battery?

No — surplus charging works without one, and the car itself acts as a large daytime "battery" for your solar. But a home battery raises the solar share on your EV from about 53% to 62% in the HTW data and, crucially, lets you charge from stored sun in the evening. Whether that extra share justifies the battery cost depends entirely on your driving pattern and roof size; it is an add-on, not a requirement.

Getting solar for EV charging

If you do not yet have a PV system, the panels are the bigger decision than the wallbox — and the price and payback vary widely by roof, region, and installer. The sensible move is to compare several quotes rather than take the first offer, then pair the system with a surplus-capable wallbox and, if it fits your schedule, a battery.

Thinking about adding solar?

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Frequently asked questions

How much of my EV charging can come from solar?

On average around 46% for a 5–10 kW rooftop system driving 10–15k km a year without a battery, rising to about 62% with a home battery (HTW Berlin field study, data to end-2024). It is much higher in summer than winter.

What does self-consumed solar actually cost me?

Roughly the foregone feed-in tariff — 7.78 ct/kWh in 2026 — because that is the income you give up by not exporting it. Against a ~37 ct/kWh grid average, each surplus kWh into the car saves about 29 ct.

What is the minimum power for solar surplus charging?

About 1.4 kW single-phase (6 A). A three-phase wallbox needs roughly 4.2 kW unless it does automatic phase switching, which lets charging start from 1.4 kW of surplus.

Which wallboxes support PV surplus charging?

Current options include the go-e Charger Gemini (with a Controller), myenergi Zappi (with a harvi sensor), KEBA P30 PV Edition, Fronius Wattpilot, and openWB. Each needs an energy meter or EMS; the Easee Home is not recommended for surplus charging.

Do I need a home battery to charge my EV from solar?

No. Surplus charging works without a battery whenever the car is plugged in during daylight. A battery mainly raises the solar share (about 53% to 62%) and enables evening charging from stored solar.

This article is for general information and is not financial or tax advice; solar economics depend on your roof, tariff, and driving pattern. Feed-in tariff (Bundesnetzagentur) and grid-price (BDEW) figures are 2026 values and change over time. Compare independent quotes before deciding.