Battery sizing Guide

Getting your battery size right makes a bigger difference than most people expect. The right capacity helps you store more daytime solar and use it at night, reduce grid use during peak times, and add real backup coverage during outages.

Most home batteries fall into two categories:

• Fixed-size batteries like Tesla Powerwall 3, which start as one set capacity and can be expanded later using Expansion Packs.
• Modular batteries, which grow by adding modules.

In this blog, we’ll explain how battery sizing works and walk through the battery systems we offer, including fixed and modular options. You’ll learn how each model scales, what the maximum capacities look like, and how to choose the right size for your home and energy goals.

Fixed sized battery

A fixed-size battery is a single unit with a set storage capacity. It’s usually the simplest option because the footprint is clean and the sizing decision is straightforward.

A strong example is Tesla Powerwall 3. It starts as a fixed-size battery, but it can scale up later using Expansion Packs. That gives you the simplicity of fixed sizing with a clear upgrade path if your usage grows.

Fixed sizing is often ideal when you want:

• a simple “choose once” battery decision
• reliable night-time coverage for bill savings
• a neat install with strong performance

Modular batteries

A modular battery system builds capacity in blocks. You start with a base number of modules and expand later by adding more.

Modular batteries suit homeowners who want:

• more control over sizing and budget
• the ability to grow storage as the household grows
• flexibility for future loads like EV charging or bigger air-conditioning use

The key advantage is simple. You can start at a practical size now, then expand later instead of replacing the system.

SolarBright’s battery range

Our current solar batteries range covers both fixed and modular sizing styles:

• Tesla Powerwall 3 (fixed-size battery, expandable with Expansion Packs)
• Tesla Powerwall 3 Expansion Pack (adds extra storage to a Powerwall 3 system)
• Sungrow SBR (modular battery, expands by adding modules)
• Sungrow SBH (modular battery, designed for higher-capacity storage builds)
• SolaX Triple Power (5.1kWh modules) (modular battery system)

Tesla Powerwall 3 and Expansion Pack

Powerwall 3 is a fixed-size battery designed for strong household coverage and a clean installation. The key sizing advantage is that you can start with one battery, then increase storage later using the Powerwall 3 Expansion Pack.

Base size, expansion steps, and maximum capacity:

• Powerwall 3 usable capacity: 13.5 kWh
• Each Expansion Pack adds: 13.5 kWh
• Maximum Expansion Packs supported: up to 3
• Maximum total storage: up to 54 kWh

That creates clear “steps” you can size to:

• 13.5 kWh (Powerwall 3 only)
• 27 kWh (Powerwall 3 + 1 Expansion Pack)
• 40.5 kWh (Powerwall 3 + 2 Expansion Packs)
• 54 kWh (Powerwall 3 + 3 Expansion Packs)

Current Powerwall 3 Deals

• Tesla Powerwall 3
• Tesla Powerwall 3 Expansion Pack
• Tesla 27kWh solar battery deal
• Energy Independence Package

These packages are built for households that want noticeable night-time coverage, stronger self-consumption, and a cleaner pathway to expand later.

Sungrow SBR

Sungrow SBR is a modular battery designed to scale by adding modules. It’s ideal if you want to start with a sensible size, then expand later as your needs increase.

Module size and maximum configuration

SBR uses modular blocks that scale storage up in steps.

• Module size: 3.2 kWh
• Minimum configuration: 2 modules (6.4 kWh)
• Maximum per stack: 8 modules (25.6 kWh)
• Maximum total storage (with supported expansion): 32 modules is 102.4kWh

This makes SBR a strong option for households that want to start mid-size and still have a high ceiling if they later want a bigger build.

Current Sungrow SBR Deals

• Sungrow SBR
• 9.6kWh Battery + 6.6kW Solar Special

Sungrow SBH

Sungrow SBH is another modular platform, often chosen when you want a higher-capacity build from day one.

Module size and maximum configuration

SBH is designed for larger storage sizing in modular steps.

• Module size: 5 kWh
• Minimum configuration: 4 modules (20 kWh)
• Maximum per stack: 8 modules (40 kWh)
• Maximum total storage (with supported expansion): 32 modules is 160kWh
• Best for: SBH suits larger homes aiming for stronger overnight coverage, heavier night loads, and higher energy independence goals.

Current Sungrow SBH Deals

• Sungrow SBH

SolaX Triple Power Battery

SolaX Triple Power uses 5.1kWh modules, making it a practical modular option when you want storage to scale in clean steps.

Module size and maximum configuration

• Module size: 5.1 kWh
• Common starting points: 10.2 kWh (2 modules) and 15.3 kWh (3 modules)
• Maximum supported storage: can scale substantially depending on model and tower configuration

This is why SolaX is popular for homeowners who want to start at a sensible capacity, then expand later rather than oversizing upfront.

Current SolaX Deals

• SolaX Triple Power Battery
• 10.2kWh Battery + 6.6kW Solar Rebate Offer
• 15.3kWh Battery + 13.2kW Solar Rebate Offer

Are these batteries qualified for rebates?

Eligibility depends on current rebate rules, your install timing, and your site details. In many cases, these battery systems can be eligible when installed and commissioned to program requirements.

The safest approach is to confirm:

• your address and state program settings
• whether rebates have been claimed at the premises before
• which battery and system configuration you’re installing

If you need help confirming rebate eligibility for your home, get in touch with SolarBright and book a free consultation.

Do you do custom solar battery installation?

Yes. Custom installs are available for both:

• battery-only upgrades (if you already have solar)
• solar and battery packages (for maximum charging performance and long-term value)

Sizing is based on your usage, tariff, goals, and future plans so you get a system that actually delivers results.

Get in touch

Get in touch to choose the right battery size.

Book a free consultation for tailored sizing advice, or call us to speak with a battery specialist today.