How Long Does a Battery Retrofit Take? What Sussex Homeowners Can Expect
Written by Green Earth Sussex — NAPIT Approved Electricians serving all of East & West Sussex.
One of the most common questions we get from Sussex homeowners considering a battery retrofit is: "How long will it actually take?" The good news is that adding battery storage to an existing solar system is usually a quick, clean process — and in most cases, your solar panels keep generating throughout the installation.
Here's a realistic breakdown of the full timeline, from your first enquiry to a fully commissioned battery system.
The Full Battery Retrofit Timeline
Initial Enquiry & Assessment (1–3 days)
After you get in touch, we'll arrange a free assessment — either a site visit or a remote assessment using photos and your existing system documentation. We'll check your current inverter, consumer unit, available wall space, and energy usage to recommend the right battery size and coupling type.
Quote & System Design (2–5 days)
Once we've assessed your system, we'll provide a detailed written quote with battery options, expected savings, and payback estimates. For most standard retrofits, this is a straightforward process. More complex systems (e.g. three-phase properties or older inverters) may require additional design time.
DNO Application (if required) (1–4 weeks)
Depending on your battery size and grid connection, a Distribution Network Operator (DNO) application may be required before installation. For most domestic systems under 3.68kW export, this is a simple G98 notification that takes just a few days. Larger systems may need a G99 application, which can take 2–4 weeks.
Installation Day (4–8 hours)
The physical installation is typically completed in a single day. Most AC-coupled battery retrofits take 4–6 hours; DC-coupled retrofits with hybrid inverter replacement may take 6–8 hours. Your solar panels will be offline for a short period during the installation but will resume generating once the new system is commissioned.
Commissioning & Handover (1–2 hours)
After installation, we commission the system, configure the battery management settings, set up your monitoring app, and walk you through how everything works. You'll receive all relevant certificates and documentation on the day.
What Happens on Installation Day?
Most homeowners are surprised by how straightforward installation day is. Here's what to expect:
- Morning arrival: Our engineers arrive, confirm the installation plan, and carry out a final check of your existing system
- Battery mounting: The battery unit is mounted on the wall — usually in a utility room, garage, or cupboard. Most modern batteries are compact and wall-mounted
- Electrical connections: The battery is wired into your existing system. For AC-coupled retrofits, this connects at the consumer unit level. For DC-coupled, the existing inverter is replaced with a hybrid unit
- Brief solar downtime: Your solar system will be offline for 1–2 hours during the connection work. This is unavoidable but kept as short as possible
- System testing: We test charge and discharge cycles, verify monitoring connectivity, and confirm backup power operation if applicable
- Handover: We walk you through the monitoring app, explain the settings, and leave you with all certificates
Factors That Can Affect the Timeline
DNO Application Type
G98 notifications are near-instant; G99 applications for larger systems can add 2–4 weeks to the timeline.
Coupling Type
DC-coupled retrofits requiring a hybrid inverter replacement take longer than AC-coupled installations.
Property Access
Difficult roof access, complex consumer unit locations, or long cable runs can add time to the installation.
Installer Availability
During busy periods (spring/summer), installation slots may be 2–3 weeks out. Booking early is recommended.
Typical Total Timeline Summary
| Stage | Typical Duration |
|---|---|
| Assessment & quote | 3–7 days |
| DNO notification (G98) | 1–3 days |
| DNO application (G99, if needed) | 2–4 weeks |
| Installation day | 4–8 hours |
| Total (G98 systems) | 1–2 weeks from enquiry |
| Total (G99 systems) | 4–6 weeks from enquiry |
Battery Retrofits Across Sussex
Green Earth Sussex installs battery retrofits throughout East and West Sussex. We cover all major towns and surrounding villages.
See the full list on our Battery Retrofits hub page.
Ready to Add Battery Storage to Your Solar System?
If you already have solar panels and want to add battery storage, the process is simpler and faster than most people expect. Our team covers all of East and West Sussex and can usually have your system assessed and quoted within a week.
Visit our Battery Retrofits page to learn more, or call us on 01273 076860 to book a free assessment.
Need Help? Get a Free Quote Today
Our NAPIT approved electricians cover all of East and West Sussex. Call us or request a free no-obligation quote.
Related Articles
Is Solar Battery Storage Worth It in Sussex? An Honest 2025 Analysis
We break down the real numbers, payback periods, and when a battery genuinely makes financial sense for Sussex homeowners.
Solar & RenewablesAC vs DC Battery Coupling: Which Retrofit Option Is Right for Your Sussex Solar System?
AC and DC coupling are two very different approaches to retrofitting battery storage. Here's how to choose the right one.
Solar & RenewablesHow to Maximise Solar Self-Consumption in Your Sussex Home
Most Sussex homeowners only use 30–40% of the electricity their solar panels generate. Here are the most effective strategies.