Retrofitting a Solar Battery: Costs and When It Pays Off in Hanover

Retrofitting a solar battery with PVPro Solar in Hanover means: a BYD battery added to your existing system. If your existing inverter is already a suitable hybrid or should stay anyway, you get BYD AC-coupled, without replacement. If it is old, not backup-capable or due for replacement anyway, we replace it with a Fronius GEN24 Plus with BYD connected directly to the DC circuit. What both routes cost, when retrofitting pays off and what really applies to VAT, backup power and registration, you will find here. Request a free, no-obligation quote now.

Retrofitting a Solar Battery: Key Facts at a Glance

Question	Answer
Possible?	in the vast majority of cases, AC-coupled or with a new hybrid inverter
Costs	approx. €3,800–15,400 depending on route and size, backup power extra
Self-consumption	rises from around 30% to up to 70%
VAT	0% when retrofitted to your own PV system on a residential building
Funding	no federal grant, but the KfW 270 loan
Registration	grid operator beforehand, Market Master Data Register; we handle both

Why Is Retrofitting a Solar Battery Worth Considering?

Anyone who only uses electricity when the sun is shining is wasting potential. During the day, when the system produces most, many residents are not at home. The surplus goes into the grid, and the feed-in tariff for new systems is only around 7.70 cents per kilowatt-hour, while in the evening you have to buy electricity for much more.A battery reverses this. It stores the midday surplus and releases it in the evening and at night. That way you use far more of your own solar power, and that is exactly what makes retrofitting a solar battery attractive for many owners.

Is Retrofitting a Solar Battery Technically Possible?

The good news first: in the vast majority of cases a battery can be retrofitted without problems. What matters is which inverter is already installed.If a modern hybrid inverter is already in place, we often connect the BYD battery directly, AC-coupled, without touching the inverter. With a pure PV system without storage preparation, or if the existing inverter is reaching the end of its life anyway, we replace it with a Fronius GEN24 Plus and connect the BYD battery directly on the DC side. Both routes work reliably; which is right depends on your existing equipment.

Retrofitting with a New Inverter: When Does It Make Sense?

AC coupling is often the simpler route, but not automatically the right one. We recommend replacing it with a Fronius GEN24 Plus if one or more of these points apply:

• The existing inverter is 8 to 12 years old or older; its typical lifespan is running out anyway.
• It has no battery input and no hybrid function, so later expansion would otherwise be limited.
• A heat pump is already planned or foreseeable; then the higher power class and backup capability are worth it straight away.

If none of these points apply, AC coupling is usually the more economical solution; your existing inverter simply stays in place.

Retrofitting a Solar Battery: The Costs

What retrofitting a solar battery actually costs depends on three things: battery size, whether your inverter stays or is replaced, and whether you want backup power. This is the breakdown for the three routes we actually offer:

Route	5 kWh	10 kWh	12–15 kWh
Battery only, hybrid inverter already in place	approx. €3,800–4,600	approx. €7,700–9,200	approx. €9,600–12,400
Battery plus new inverter: AC-coupled with its own battery inverter, or replacement with a Fronius GEN24 Plus	approx. €5,300–7,600	approx. €9,200–12,200	approx. €11,100–15,400
PV Point socket backup	+ approx. €300–800
Full backup for the whole house	+ approx. €1,200–1,800 (changeover device, if the inverter is already backup-capable; if not, the new inverter from the table comes on top)

PV Point and full backup are two different products at two different prices, not a single backup item. PV Point supplies a single socket with up to 3 kW, only while the sun is shining. Full backup supplies the whole house, also at night, but needs a changeover device for safe grid disconnection in addition to the battery.The prices above are guide values and match the BYD battery prices we also quote for new systems (BYD HVS 5.1 approx. €3,800–4,600, HVS 10.2 approx. €7,700–9,200). A new inverter or battery inverter costs about €1,500–3,000 extra. They are not quoted fixed prices for your specific project. Your actual price depends on the meter cabinet, roof position and cable route; we clarify this in the quote.

Is There VAT on the Battery?

The zero VAT rate does not apply across the board to “photovoltaics and storage”. It applies at 0 % if the battery is bought together with a PV system, or if it is retrofitted to an existing PV system that you operate yourself on a residential building. If you buy the battery on its own, without any link to a PV system, or retrofit it to a system you do not operate yourself, the full rate of 19 % may apply instead. We check this for your specific case before we write the quote.

Increasing Self-Consumption: The Real Goal

The main reason for retrofitting is to increase self-consumption. Without storage, the self-consumption rate of a typical system is often only around 30 per cent. With a suitably sized battery it often rises to up to 70 per cent.What does that mean in practice? Every kilowatt-hour you use yourself replaces expensive grid electricity instead of earning the low feed-in tariff. How much that adds up to over the years is shown in the following example.

Is Retrofitting a Solar Battery Really Worth It? An Example Instead of a Rule of Thumb

Take an 8 kWp system and 5,000 kWh annual consumption. Self-consumption rises with storage from around 30 to around 70 per cent, i.e. about 2,000 kWh a year that are used yourself instead of fed in. With an assumed electricity price of 37 cents and a feed-in tariff of 7.70 cents per kilowatt-hour, that saves around €590 a year (2,000 kWh × around 29 cents difference).A 10 kWh battery for around €7,700 to €9,200 takes about 13 to 16 years in this calculation to pay for itself through higher self-consumption alone. If you also use a heat pump or a wallbox that absorbs the midday surplus, this time shortens noticeably because the battery is then discharged more often and more deeply.One important limitation: if your system still receives a high EEG feed-in tariff from 2018 to 2020, often over 10 cents per kilowatt-hour and guaranteed for 20 years from commissioning, a battery often pays off less or not at all. Every kilowatt-hour you then store instead of feeding in gives up an already secured, comparatively good tariff. The roughly 7.70 cents of feed-in tariff that make retrofitting really attractive only apply to new systems, not to your existing system from that period.

AC or DC: How Your Solar Battery Can Be Retrofitted

There are two basic routes for retrofitting a battery:

• AC coupling: the BYD battery gets its own battery inverter and is connected on the AC side. Your existing inverter remains untouched.
• DC coupling: the BYD battery is connected directly to the DC circuit, in our case via the Fronius GEN24 Plus. Somewhat more efficient, but requires this inverter to be either already in place or installed as part of the retrofit.

For retrofitting an existing system, AC coupling is in practice often the simpler solution; see also the section above on inverter replacement. Which option makes more sense for you is clarified by an individual on-site analysis.

When Does Retrofitting Pay Off, and When Not?

To be honest: a battery does not pay off equally well in every case. Retrofitting tends to be worth it if these points apply:

1. High electricity consumption, especially in the evening and at night.
2. A planned or existing wallbox or heat pump that further increases self-consumption.
3. High electricity prices for grid power.
4. Surplus solar power that has so far mostly been fed in.

Retrofitting makes less sense if your consumption mainly takes place during the day, you already achieve a high self-consumption rate, or your system still receives the high EEG feed-in tariff from 2018 to 2020; see the example above. Serious advice tells you this openly instead of selling you a battery at any price.

Post-EEG Systems: A Battery After the Feed-In Tariff Ends

The EEG feed-in tariff applies for 20 years plus the year of commissioning. After that, the system may keep running, but power fed into the grid only earns the market value of solar power minus marketing costs, recently just a few cents per kilowatt-hour. That makes a battery particularly interesting for post-EEG systems: every kilowatt-hour you use yourself saves the full electricity price instead of earning almost nothing.

Have two points checked: many old systems feed in all their power and first have to be converted to self-consumption, usually with changes to the meter cabinet and meter. And an inverter from the early years is almost always at the end of its life, in which case replacing it with a Fronius GEN24 Plus and a BYD battery is usually the better route. More on inverters under solar inverters.

Funding for a Retrofitted Battery

There is no nationwide grant for private batteries, and the Hanover Region’s Dach-Solar programme and proKlima DachVollToll fund the module area or the PV system, not the battery. What remains is the zero VAT rate, see above, and the low-interest KfW 270 loan, which is a loan, not a grant. All programmes in the region are listed under solar funding in Hanover.

The Paperwork: What Has to Happen Before Switching On

A retrofitted battery needs its own registration in the Market Master Data Register, separate from the PV part, and a notification to the responsible grid operator, in Hanover usually enercity Netz. The grid operator is notified before commissioning, and the registration in the Market Master Data Register follows within one month at the latest. We take care of this paperwork for you as part of the installation, not as an extra job you have to sort out yourself.

Conclusion

If you want to retrofit a solar battery, it is a sensible decision in many cases, provided battery size, coupling type and your own EEG tariff fit your individual case. In Hanover we retrofit BYD for this, AC-coupled if your inverter can stay, or with a Fronius GEN24 Plus if it is being replaced anyway. Our local battery service with all prices is described under battery storage in Hannover.Would you like to know whether and how a battery pays off for your system? As a regional specialist from Hanover, we check your existing system and advise you honestly and without sales pressure.Request your free quote now or call us directly on +49 511 3360603. If you want to read up on the basics of battery storage first, start with power storage for your home; a comparison of brands and test results is under best battery storage, and the costs of a 5 kWh system are under 5 kWh battery storage.

Retrofitting a solar battery: is it possible with an existing system?

Yes, in the vast majority of cases this is no problem. With an existing, suitable hybrid inverter we often connect the BYD battery directly AC-coupled without replacing the inverter. If the existing inverter is unsuitable or outdated, we replace it with a Fronius GEN24 Plus and connect the BYD battery directly on the DC side.

What does retrofitting a solar battery cost?

It mainly depends on whether your inverter stays or is replaced. If a suitable hybrid inverter is already in place, the BYD battery costs around €3,800 to €12,400 depending on size, around €7,700 to €9,200 for 10 kWh. If a new inverter or battery inverter is needed, around €1,500 to €3,000 comes on top. Backup power costs extra: a simple socket backup from around €300, full backup for the whole house from around €1,200.

How many kWh of storage do I need?

As a rough rule of thumb, a storage capacity roughly equal to daily consumption often fits, usually between 5 and 10 kWh for a single-family home. With a heat pump or wallbox, more makes sense. What matters is your individual consumption profile, which we go through with you in the consultation.

How much does my self-consumption rise with a battery?

Without storage, the self-consumption rate is often around 30 per cent. With a suitably sized battery, self-consumption can often be raised to up to 70 per cent. With 5,000 kWh annual consumption and an 8 kWp system, that corresponds to around 2,000 kWh a year used yourself instead of fed in.

Do I have to replace my inverter for the retrofit?

Not necessarily. With AC coupling the existing inverter stays and the BYD battery gets its own battery inverter. If your inverter is older than 8 to 12 years, not hybrid-capable, or you are planning a heat pump, we recommend replacing it with a Fronius GEN24 Plus with direct DC coupling.

Is there VAT on the battery?

Not across the board. The zero VAT rate applies if the battery is bought together with a PV system or retrofitted to an existing PV system that you operate yourself on or at a residential building. A battery without any link to a PV system, or for a system you do not operate yourself, may still be taxed at 19 %.

Is a battery worth it despite the low feed-in tariff?

For a new system precisely because of it, since the feed-in tariff there is only around 7.70 cents per kilowatt-hour and self-used electricity is correspondingly more valuable. If your system still receives the high EEG tariff from 2018 to 2020, often over 10 cents and guaranteed for 20 years, a battery often pays off considerably less.

Does PVPro Solar carry out retrofits in the Hanover region?

Yes. As a regional specialist from Hanover, we check your existing system, size the right BYD battery, handle AC or DC coupling and take care of installation, MaStR registration, grid operator notification and monitoring from a single source.

Is a battery worth it for a post-EEG system?

Often, yes. After the EEG tariff ends, power fed into the grid only earns the market value, recently a few cents per kilowatt-hour. Every kilowatt-hour you use yourself saves the full electricity price instead. Many old systems first have to be converted to self-consumption, and the old inverter is usually replaced at the same time.

Is there funding for a retrofitted battery?

There is no nationwide grant, and the programmes in the Hanover region fund the PV system, not the battery. What remains is the zero VAT rate and the low-interest KfW 270 loan.