What Size Solar Battery Do I Need?

Not sure whether you need a 5kWh, 10kWh or 13kWh+ battery? This guide helps you work out the right battery capacity for your Central Coast home based on your energy usage, solar system size and what you want the battery to do.

The Quick Answer

How to Work Out Your Battery Size

The right battery size comes down to one key number: how much electricity your household uses between sunset and sunrise. This is your “evening and overnight consumption” — the energy your solar panels can’t provide because the sun isn’t shining. A battery stores your surplus daytime solar to cover this gap.

A typical Central Coast household uses between 8–15 kWh between sunset and sunrise. So for most homes, a battery in the 10–13.5 kWh range covers the majority of your evening and overnight needs. A smaller 5 kWh battery covers the peak evening hours but runs out before morning. A larger 15–20 kWh battery provides near-complete overnight coverage and whole-home blackout protection.

The simplest way to estimate your ideal battery size is to look at your energy usage data on your monitoring app or electricity bill, focusing specifically on what you consume outside of solar generation hours. During your free consultation, we analyse your actual data to recommend the exact right size.

Battery Sizes Compared

Solar Battery Sizes at a Glance

Here’s how the three most common home battery capacities compare for a typical Central Coast household.

5kW

Entry Level

Covers your peak evening usage (cooking, TV, lights) for 2–4 hours after sunset. Will likely run out before midnight on most nights.

Evening Coverage

2 – 4 hours

Best For

1 – 2 person household

Solar System

5 – 6.6kW

Self-Consumption

60 – 70%

Blackout Backup

Essentials only

10kW

Standard Home

Covers most of your evening and overnight usage. Enough for a typical family to run through to early morning before needing the grid.

Evening Coverage

8 – 12 hours

Best For

3 – 4 persons

Solar System

6.6 – 10kW

Self-Consumption

80 – 90%

Blackout Backup

Essential circuits

13.5kW

Large Home

Near-complete overnight coverage for larger households. Handles high evening consumption from pool pumps, AC, and EV charging.

Evening Coverage

12 – 18 hours

Best For

4+ persons

Solar System

10 – 13kW

Self-Consumption

85 – 95%

Blackout Backup

Whole home capable

Solar + Battery Pairing

What Size Battery for My Solar System?

Your solar system size determines how much surplus energy is available to charge your battery each day. Here’s a guide to how different solar system sizes pair with common battery capacities on the Central Coast.

*Daily surplus varies by season, roof orientation and household daytime usage. Winter surplus is lower than summer. These figures are based on typical Central Coast conditions with north-facing panels.

Important: you don’t need a battery large enough to store all your surplus. You only need enough to cover what you’d otherwise buy from the grid in the evening and overnight. Any surplus beyond your battery’s capacity still gets exported for a feed-in tariff — it doesn’t go to waste.

Solar System Daily Surplus (typical) Recommended Battery Result
5–6.6 kW 8–15 kWh 5–10 kWh Covers peak evening. Some grid overnight.
6.6–10 kW 15–25 kWh 10–13.5 kWh Covers most evening & overnight usage.
10–13 kW 25–35 kWh 13.5–20 kWh Near-complete overnight. Minimal grid use.
13 kW+ 35+ kWh 20+ kWh Full coverage. Near energy independence.

Factors to Consider

What Else Affects Your Battery Size Decision?

Beyond your basic evening consumption, there are several other factors that may influence the optimal battery capacity for your home.

Time-of-Use Tariffs

If you’re on a time-of-use electricity plan, peak rates (typically 2pm–8pm) are significantly higher. A battery that covers this peak window saves you the most money — even a smaller battery focused on peak hours can deliver strong ROI.

Blackout Protection

If keeping your home powered during grid outages is a priority, you’ll want a larger battery (13.5kWh+) with backup capability. A 10kWh battery can run essential circuits (lights, fridge, internet) for 8–12 hours during an outage.

Future Energy Needs

Planning to get an EV, add a pool, or switch from gas to electric appliances? Your future energy consumption may be higher than today. Consider sizing up now to avoid needing a second battery later.

Budget

A bigger battery saves more, but costs more upfront. The sweet spot for most households is a 10–13.5kWh battery — it covers the bulk of your evening usage without oversizing. You can always expand modular batteries like the Sungrow SBR or Enphase IQ later.

The key point: these two incentives can be stacked. A typical Central Coast household installing a 10kWh battery can receive approximately $3,000–$3,400 from the federal program plus up to $1,500 from the NSW VPP incentive — a combined saving of $4,500+ before you’ve even started reducing your electricity bills.

Not Sure? We’ll Analyse Your Usage Data for Free

During your consultation, we review your actual energy consumption and recommend the exact right battery size — no guesswork.

Frequently Asked Questions

Battery Sizing FAQs

Common questions about choosing the right size solar battery for your home.

A 5kWh battery covers 2–4 hours of typical evening usage — enough for lights, cooking and entertainment during peak evening hours. However, it will likely run out before midnight, meaning you’ll still draw from the grid overnight. A 5kWh battery is best suited to small households (1–2 people) with low evening consumption, or as a budget entry point for peak-hour tariff savings.

For most Central Coast families (3–4 people), a 10kWh battery covers the majority of evening and overnight usage — typically 8–12 hours of power. It’s the most popular size we install and offers the best balance between coverage and cost. You may still draw a small amount from the grid in the early morning hours or on very high-consumption evenings, but overall you’ll achieve 80–90% self-consumption.

A 6.6kW solar system typically produces 8–15kWh of surplus energy per day (after your home uses what it needs during daylight hours). A 10kWh battery is the ideal match — it stores most of the surplus without being oversized. A 5kWh battery works for smaller households, but you’ll export more surplus than you store. A 13.5kWh battery is an option if you have high evening consumption.

Yes — if you choose a modular battery like the Sungrow SBR or Enphase IQ, you can start with a smaller capacity and add modules later as your needs grow or budget allows. The Sungrow SBR starts at 9.6kWh and can expand to 25.6kWh by adding 3.2kWh modules. Enphase IQ batteries can be stacked in 5kWh increments. Tesla Powerwall units can also be added alongside each other (up to 3 units). We’ll advise on the best expandable option during your consultation.

If you have solar monitoring (like the Fronius, Enphase or Sungrow app), check your daily consumption graph and look at how much electricity you import from the grid between sunset and sunrise. That number is your evening/overnight consumption — and it’s the amount a battery needs to cover. If you don’t have monitoring, your electricity retailer’s usage data (often available via their app or portal) shows the same information. During our consultation, we pull this data and analyse it for you.

Not necessarily. An oversized battery costs more upfront but may not fill completely each day — especially in winter when solar production is lower. The sweet spot is a battery that covers your typical evening and overnight usage without being significantly larger than what your solar system can charge. That said, if you’re planning to add an EV, pool or more appliances in the next few years, a slightly larger battery now can be a smart investment. We help you balance current needs with future-proofing during the consultation.