Blog Details

10kWh vs 13.5kWh vs 20kWh Battery: What Size Battery Does Your Home Need?

Solar Batteries
Sep 12, 2026
25 minutes read
60 Views

Not sure whether you need a 10kWh, 13.5kWh or 20kWh battery? Compare battery capacity, solar surplus, evening usage, EVs, backup and costs to find the right size for your home.

Battery Storage

10kWh vs 13.5kWh vs 20kWh Battery: What Size Battery Does Your Home Need?

If you're looking at home batteries, you've probably already come across three numbers: 10kWh, 13.5kWh, and 20kWh.

At first glance, the decision looks simple.

"I have a big house, so I should get the 20kWh battery."

But that's not how battery sizing really works. A battery isn't sized according to the number of bedrooms in your home. It is sized around how much solar energy you have available to store, how much electricity your home uses after solar production falls, how often the battery can be charged and discharged, and what you want the battery to do.

For some Melbourne households, 10kWh may be enough. For a home with higher evening consumption, 13.5kWh can provide a useful middle ground. And for a high-energy household with a large solar system, EV, heat pump or significant evening demand, 20kWh may be worth considering — but only if the solar system can regularly charge it and the household can use the stored energy.

Solar Victoria's current guidance specifically warns against simply buying the largest battery available. The battery should be regularly charged and discharged to an appropriate level, with sizing based on solar generation, overnight consumption and backup requirements.

So the real question is: Which battery size fits the way your home actually uses electricity?

Quick Answer: 10kWh vs 13.5kWh vs 20kWh

Battery	Best For	Main Advantage	Main Risk
10kWh	Moderate evening household	Lower upfront	May be too small if solar surplus is limited
13.5kWh	Medium/high-use homes	Large solar + higher evening demand	Capacity and flexibility
20kWh	High-energy homes	More stored energy and greater flexibility	Higher cost and may remain under-utilised

These are planning categories, not universal recommendations. A 20kWh battery isn't automatically better than a 10kWh battery.

If your solar system cannot regularly charge 20kWh of usable storage, or your home doesn't consume the stored electricity, the additional capacity may not deliver enough value to justify its cost.

First: What Does "10kWh Battery" Actually Mean?

This is important because battery marketing can make comparisons confusing. kWh = kilowatt-hours. It describes the amount of energy a battery can store.

So, in simple terms:

10kWh battery → about 10kWh of nominal stored energy
13.5kWh battery → about 13.5kWh nominal
20kWh battery → about 20kWh nominal

But don't stop at the headline number. You should also ask:

What is the usable capacity?

A battery may have a nominal capacity that is higher than the energy the homeowner is actually permitted or expected to use.

What is the continuous power output?

A 20kWh battery with limited power output may not be able to run several large appliances simultaneously.

What is the round-trip efficiency?

Energy is lost during charging and discharging.

What happens to capacity over time?

Battery capacity decreases as the battery ages. Solar Victoria recommends asking what usable capacity will remain around the end of the warranty period, rather than looking only at the battery's new capacity.

The Golden Rule of Battery Sizing

A battery should be big enough to store useful surplus solar, but not so big that most of it sits unused.

Solar Victoria's current guidance says the best financial outcome generally comes from a battery that is regularly charged and discharged to the recommended level. It also warns against buying a battery that is too large for the available solar or household demand.

Think about your battery like a water tank. If your roof collects 10 litres of water per day, there isn't much point installing a 50-litre tank if you rarely collect enough water to fill it. Solar works in a similar way.

10kWh Battery

Who is a 10kWh battery best for?

A 10kWh battery can be a sensible starting point for households with:

Moderate electricity consumption
A reasonably sized solar system
Meaningful evening electricity use
Moderate overnight demand
Limited daytime solar self-consumption
No exceptionally large electrical loads

It can be particularly attractive when the goal is: "I want to store enough of my surplus solar to cover a good portion of my evening usage" rather than "I want my house completely independent from the grid."

Where 10kWh Wins

Lower initial investment — All else being equal, a smaller battery requires less storage capacity. That can make the financial calculation easier to justify.

Easier to keep well utilised — If your solar surplus is moderate, a 10kWh battery may reach a useful state of charge more often than a much larger battery.

Good for moderate evening loads — If your household typically uses several kWh after sunset rather than 15–20kWh, a 10kWh system may be enough to make a meaningful difference.

Can work well with medium-sized solar — A moderately sized solar system may not consistently have enough surplus energy to fill a 20kWh battery.

When 10kWh May Be Too Small

You may need to look at a larger battery if your home has high evening electricity consumption, multiple air conditioners, electric hot water, large heat-pump loads, a pool, an EV, a large family, high overnight usage, substantial solar exports, or backup requirements. For example, if your home regularly needs 12–15kWh after solar production has stopped, a 10kWh battery may not cover all of that demand. That doesn't necessarily make the 10kWh battery a bad choice.

13.5kWh Battery

Why is 13.5kWh such an interesting size?

13.5kWh sits in the middle. It gives you more storage than a 10kWh system without jumping all the way to 20kWh. For many higher-consumption households, that can make it a useful compromise.

Samsun Energy currently has real residential projects using 13.5kWh battery systems, including:

10kW solar + 13.5kWh AlphaESS in Hoppers Crossing
10.5kW solar + 13.5kWh Sungrow battery in Geelong

Those are real Samsun project examples, but they should not be interpreted as proof that every 10kW solar system needs a 13.5kWh battery. The important lesson is that battery capacity is being matched with the broader solar and household energy system.

Where 13.5kWh Wins

More evening coverage — Compared with 10kWh, additional capacity can provide more stored energy for later use.

Good fit for larger solar systems — A home with 10kW or 10.5kW of solar may have more surplus energy available to store than a smaller solar installation.

Future flexibility — If the household is planning EV charging, electric hot water, heat pumps, additional air conditioning, or greater electrification, the additional capacity may provide useful headroom.

Middle-ground economics — You don't always need to jump from a 10kWh battery directly to 20kWh. A 13.5kWh system can be a practical compromise.

When 13.5kWh May Be Too Large

Suppose your household only exports 3–5kWh of solar per day on average. A 13.5kWh battery may rarely charge anywhere near its usable capacity from solar. You could still charge from the grid where the system and tariff allow it, but that changes the economics. The battery should therefore be assessed against your actual export data.

20kWh Battery

Who should consider 20kWh?

A 20kWh battery is generally more relevant to a high-energy household rather than an average home. It may be worth investigating when you have several of the following:

Large solar system
High annual electricity consumption
High evening electricity demand
Large family
EV
Electric hot water
Heat pump
Multiple air conditioners
Pool equipment
High overnight consumption
Backup requirements

The key word is: Demand. If the home genuinely uses a lot of electricity after solar production has ended, a larger battery may have a role.

Where 20kWh Wins

More stored energy — There's simply more energy available for later use.

Higher evening demand — If your home uses 15–20kWh after sunset, a 20kWh battery may be more appropriate than a 10kWh battery.

Large solar systems — A sufficiently large solar system can provide more energy to charge a larger battery.

Future electrification — If your household is transitioning toward Solar + battery + EV + heat pump + electric appliances, future electricity demand may justify a larger storage system.

The Big Problem With 20kWh: It Can Be Too Much Battery

This is the part battery advertisements don't always emphasise. If your solar system only produces enough surplus to charge 6–8kWh on many days, what is going to charge the remaining capacity? And if your household only uses 6–8kWh after sunset, why pay for substantially more storage?

A larger battery can make sense. But it needs a job to do.

The Solar-to-Battery Relationship

This is one of the most important calculations. Imagine three homes.

Home A

6.6kW solar
Daily surplus available for battery: ~5kWh
A 20kWh battery may be difficult to utilise fully.

Home B

10.5kW solar
Daily surplus: ~10–14kWh
A 13.5kWh battery may be much easier to utilise.

Home C

13.2kW solar
High household consumption + significant daily surplus: ~15–20kWh
A larger battery may become more reasonable.

These numbers are illustrative only. Actual surplus depends on location, season, shading, roof orientation, household consumption and solar generation. Solar Victoria specifically recommends sizing batteries around actual solar generation and household usage rather than selecting a battery simply because it has more capacity.

Your Evening Electricity Use Is Even More Important

Look at your household after sunset. Suppose your solar stops meaningfully contributing around evening. From 5pm → midnight your household uses 9kWh. A 10kWh battery may already be enough to cover most of that energy requirement, subject to usable capacity, losses and battery operating limits.

Buying 20kWh doesn't necessarily double your savings. You may simply have unused capacity.

Now imagine another household uses 16kWh between sunset and midnight. Here, a larger battery becomes more interesting.

This is why your electricity bill is more useful than your house size. Don't say: "We have five bedrooms, so we need 20kWh." Instead ask: How many kWh do we use after solar generation falls? Then ask: How much of that electricity could realistically come from stored solar? That's the number that matters.

10kWh vs 13.5kWh vs 20kWh: A Practical Comparison

Factor	10kWh	13.5kWh	20kWh
Moderate household	★★★★	★★★	★★
Larger family	★★	★★★★	★★★★
High electricity usage	★★	★★★	★★★★★
Large solar system	★★	★★★★	★★★★★
EV household	★★	★★★★	★★★★★
Heat-pump / electrified home	★★	★★★★	★★★★★
High evening usage	★★	★★★★	★★★★★
Lower upfront investment	★★★★★	★★★	★★
Easy to keep utilised	★★★★★	★★★★	★★★
Maximum stored energy	★★	★★★	★★★★★
Backup potential	Depends on inverter / load

The stars are a planning comparison, not a performance rating. Battery power output, usable capacity and backup design can matter just as much as kWh capacity.

Don't Confuse Battery Capacity With Battery Power

This is one of the most important technical distinctions.

kWh

Tells you how much energy can be stored.

kW

Tells you how much power the battery/inverter can deliver at a given time.

Imagine you have a 20kWh battery but its inverter can't provide enough power for several large appliances running simultaneously. You may have plenty of stored energy, but insufficient instantaneous power. That's why a battery quote should show both.

So don't ask only: "How many kWh is the battery?" Also ask: "What continuous and peak power can the battery system deliver?"

Usable Capacity vs Advertised Capacity

Suppose a battery is advertised as 13.5kWh. Ask: "How much of that capacity is actually usable?" Then ask: "What will the usable capacity be near the end of the warranty?"

Battery systems are designed with operating limits that protect the battery and support its life. The number printed on the brochure isn't necessarily the amount of energy you'll repeatedly use from 0% to 100%. Solar Victoria specifically recommends checking end-of-life usable capacity when comparing battery systems.

What happens to battery capacity over time?

Batteries don't stay exactly the same forever. Capacity gradually declines. That's why warranty terms matter. Compare Year 1 capacity with Year 10 guaranteed capacity rather than looking only at the starting number.

A battery advertised as 20kWh may still be useful after many years, but the amount of usable energy available at that point depends on the product's warranty and degradation terms.

10kWh vs 13.5kWh vs 20kWh for Different Homes

Small / Moderate Household

Typical situation: 2–3 occupants, moderate electricity use, 6.6kW solar, moderate evening demand, no EV.

Consider: 10kWh. The priority is keeping the battery well utilised. A 20kWh battery could be unnecessary.

Growing Family

Typical situation: 3–5 occupants, larger home, 10kW+ solar, air conditioning, higher evening consumption, possible EV.

Consider: 13.5kWh. This can provide a useful balance between storage and investment.

High-Energy Home

Typical situation: Large family, 10–13kW+ solar, multiple air conditioners, electric hot water, pool, EV, high evening demand.

Consider: 13.5kWh or 20kWh. The deciding factor should be actual electricity data. If the home consistently has enough solar surplus and evening demand to use the additional capacity, 20kWh deserves consideration.

EV Owner

An EV changes the calculation. Suppose the car is away during the day and home in the evening. The household may want to use stored solar to charge the vehicle. But a large battery isn't automatically the answer.

Ask: How many kWh does the EV need each day? When is it home? Can it charge directly from solar? Can charging be scheduled? What is the EV charger power? A home with an EV can potentially have much greater electricity demand than a similar home without one.

Heat Pump + Battery

Heat-pump hot water can create a useful daytime electricity load. Instead of:

Solar → Grid

you can potentially have:

Solar → Heat Pump → Hot Water

The hot water then acts as a form of thermal storage. This can reduce the amount of surplus electricity that needs to be stored in a battery.

So before buying a bigger battery, consider whether your home has flexible loads that can be moved into solar hours. Solar Victoria specifically recommends shifting flexible energy use into the daytime and gives hot-water systems as an example of how surplus solar can be used.

What If You Work From Home or Are Away During the Day?

Work From Home

This can reduce the battery size you need. If you are using electricity during the day, Solar → Home is already doing the job. You don't need to store electricity you're going to use immediately. A household that works from home may therefore have different battery requirements from a household that is empty from 8am to 5pm.

Everyone Away During the Day

Now the situation changes. You may generate a lot of solar when nobody is home. That creates Solar surplus → Grid export. A battery can potentially capture some of that energy for evening use. This is one of the situations where battery storage can be particularly useful. Solar Victoria identifies households that are often out during the day but have high evening and morning consumption as a group that may benefit from batteries.

What About a Battery for Blackout Backup?

This is another reason people choose a larger battery. But: battery capacity and backup capability are not the same thing.

A 20kWh battery does not automatically mean: "My entire house will run for 20 hours."

Your actual backup runtime depends on:

Usable battery capacity
Inverter output
Household load
Essential circuits
Appliances running
System configuration

Solar Victoria says a battery can provide backup during a grid outage only when the system is designed for backup, and not all storage systems provide this functionality.

10kWh vs 13.5kWh vs 20kWh for Backup

Imagine essential backup loads consume 1kW average. Very roughly:

10kWh battery — could provide around 10 hours of stored energy before accounting for system losses and operating limits.
13.5kWh — potentially around 13.5 hours.
20kWh — potentially around 20 hours.

But these are not real-world guaranteed runtimes. If the home suddenly runs heating, cooking, air conditioning or hot water, the battery can discharge much faster. And inverter power limits may prevent some loads from operating simultaneously. Always ask the installer to model your actual backup loads.

Battery Size and the 2026 Federal Incentive

There is another reason not to automatically choose 20kWh. Under the current Australian Government Cheaper Home Batteries Program, eligible battery installations receive support through the Small-scale Renewable Energy Scheme.

For 2026, the STC treatment is not a flat percentage applied equally to every kWh. For May–December 2026:

First 14kWh receives the full STC factor
14kWh to 28kWh receives 60%
28kWh to 50kWh receives 15%
The 2026 STC factor is 6.8

So the first 14kWh has a different incentive treatment from the additional capacity. This doesn't mean: "Never buy a 20kWh battery." It means: Don't assume the extra 6.5kWh receives the same incentive value as the first 13.5kWh.

The financial calculation should use the current rules and the actual quote.

The Economics: Bigger Battery Doesn't Automatically Mean Better Payback

This is probably the most important financial point.

10kWh Battery

Costs less
Provides meaningful evening storage
Is regularly charged
Is regularly discharged

20kWh Battery

Costs considerably more
Only reaches 50–60% charge on many days
Household doesn't use all the stored energy

The 10kWh system could potentially deliver a better return despite having less storage. Solar Victoria's current modelling explicitly notes that battery payback is highly sensitive to sizing, and that smaller batteries can have quicker payback than larger systems in some circumstances.

What determines battery payback?

Battery purchase price — The actual installed cost.
Incentive — Current STC value and eligibility.
Solar exports — How much surplus electricity would otherwise go to the grid.
Feed-in tariff — How much you'd receive for that exported electricity.
Electricity import rate — How much you're avoiding by using stored energy.
Battery utilisation — How often and how deeply the battery cycles.
Efficiency — Energy lost during charging and discharging.
Degradation — Capacity decline over time.
Future electricity use — EVs, heat pumps and other loads can change the economics.

A Simple Battery Value Example

Imagine you export 10kWh of solar during the day. Your feed-in tariff is 5c/kWh.

Export value: $0.50

If instead you store and later use 8kWh after accounting for losses, and those 8kWh replace electricity you would otherwise buy at 35c/kWh, the avoided purchase could be:

Avoided purchase: $2.80

The gross difference is $2.30. But that's not your battery saving. You still need to account for battery cost, installation, degradation, financing, maintenance, efficiency, and opportunity cost.

The example simply shows why the relationship between FiT and grid electricity prices matters.

What If I Have a Low or High Feed-in Tariff?

Low Feed-in Tariff

A lower FiT can make storing solar more attractive. If your retailer pays only a few cents for exported solar while your grid electricity costs substantially more, there is a larger difference between exporting and using stored energy later. But again: battery cost determines whether that difference is enough to justify the investment.

High Feed-in Tariff

Then the economics become less obvious. If you're already receiving a relatively attractive export rate, you are giving up more value when you divert solar into the battery. That's why a battery should be assessed using your actual electricity plan, not a generic Victorian tariff.

10kWh vs 13.5kWh vs 20kWh: Who Should Choose What?

Choose 10kWh when:

Your solar surplus is moderate
Evening usage is moderate
You want to keep the upfront cost under control
You want a battery that is easier to utilise regularly
You don't have unusually high electricity demand

Best fit: Moderate household + moderate solar surplus.

Choose 13.5kWh when:

Your solar system is larger
Evening usage is higher
You have a growing family
You are adding an EV or heat pump
You want more storage without jumping to 20kWh
Your solar exports justify the additional capacity

Best fit: Medium/high electricity use + substantial solar surplus.

Consider 20kWh when:

Your home genuinely uses a lot of electricity
You have a large solar system
Evening/overnight demand is high
You're adding an EV
Your home is becoming heavily electrified
Backup requirements are significant
The battery can be regularly charged and discharged

Best fit: High-energy home + high solar surplus + high evening demand.

What Samsun Energy's Current Projects Show

Samsun's residential portfolio provides useful real examples of different solar-and-battery combinations.

Smart Storage – Wyndham Vale

6.6kW solar + 10kWh Dyness — Installed August 2024.

Battery Storage – Hoppers Crossing

10kW solar + 13.5kWh AlphaESS — Installed September 2024.

Future-Ready Home – Geelong

10.5kW solar + 13.5kWh Sungrow battery + EV-ready — Installed July 2024.

These examples are useful because they show that 10kWh and 13.5kWh batteries are already being used across different residential solar configurations. They don't establish a universal rule such as: "6.6kW solar always needs 10kWh." Every property still needs its own assessment.

What About 20kWh?

A 20kWh system can absolutely make sense. But it should be treated as a high-capacity storage decision, not simply an upgrade from 13.5kWh. Before choosing it, ask:

Can my solar regularly charge it?
Will my household regularly use the stored energy?
Do I need the additional capacity for backup?
Do I have an EV?
Am I planning major electrification?
What is the incremental cost?
What is the incremental saving?
What is the incremental payback?

That final question is often overlooked.

Compare the Incremental Battery Cost

Don't ask only: "What does a 20kWh battery cost?" Ask: "What does the extra 6.5kWh from 13.5kWh to 20kWh cost me, and what additional value will it provide?" That is a much better buying question.

For example: 13.5kWh → 20kWh

Additional capacity: 6.5kWh

Now calculate: Additional installed cost + additional annual benefit = incremental payback. If the extra capacity is rarely used, the incremental payback could be unattractive.

Modular Batteries Can Change the Decision

Some battery systems are modular. That means you may be able to start smaller and add capacity later. Solar Victoria notes that some systems allow future capacity expansion, although the ability to expand depends on the battery architecture and must be confirmed before purchase.

This can be useful if:

Your current electricity use is moderate
You're planning an EV
Your family is growing
You want to spread the investment
You're unsure how much storage you actually need

But don't assume every battery can be expanded. Ask: "Can I add modules later, and under what conditions?"

Don't Buy Battery Capacity You Can't Charge

This sounds obvious. But it's one of the easiest mistakes to make. Your solar system might produce plenty of electricity in summer. But what happens in winter?

Melbourne has shorter days and lower solar generation during winter. Your battery may therefore behave very differently across the year. Solar Victoria notes that seasonal solar generation and household demand should be considered when sizing a battery.

A battery that looks perfect on a sunny January day may be significantly harder to fill during cloudy winter periods.

Don't buy a battery that's too small either

The opposite problem exists. If your home consistently exports 15kWh+ during the day and uses 12–15kWh after sunset, a 10kWh battery may leave substantial potential storage unused. That's where 13.5kWh or 20kWh can become worth investigating.

The goal is:
Not too small. Not too large. Right-sized.

What About Battery Brands?

Battery size is only one part of the decision. Samsun Energy currently lists:

AlphaESSSungrowDynessGoodWe Lynx

When comparing brands, look beyond capacity. Check:

Usable capacity
Inverter compatibility
Continuous output
Warranty
End-of-warranty capacity
Chemistry
Operating temperature
Expansion capability
Backup capability
VPP compatibility
Monitoring
Installation requirements
Local support

Two 13.5kWh batteries can be very different products.

What About Battery Chemistry?

Most modern residential lithium batteries use lithium-based chemistry. Solar Victoria's current buyer guidance discusses lithium-ion systems, including LFP/LiFePO4 and NMC chemistries.

Don't choose solely on the chemistry label. Look at the complete product:

Chemistry + warranty + usable capacity + power output + safety + installation + support

Battery Location Matters

A 20kWh battery also isn't just: "Put a bigger box on the wall." Larger systems can have greater physical and installation requirements.

Solar Victoria advises that batteries should be installed in suitable locations, protected from hazards and direct harsh environmental exposure, and not inside domestic habitable rooms under the applicable Australian safety standards. Your installer should check:

Wall/floor mounting
Clearances
Weather exposure
Temperature
Accessibility
Fire safety requirements
Electrical equipment
Switchboard position

What About VPPs?

A battery can potentially participate in a Virtual Power Plant (VPP). A VPP connects multiple batteries through software so stored energy can be managed collectively.

Solar Victoria says VPP-ready systems need to meet certain technical capabilities, and programs can have their own product requirements. If VPP participation interests you, ask:

Is this exact battery eligible?
Which VPPs support it?
What are the payments?
What control does the retailer have?
Can I leave the program?

Don't assume every battery automatically qualifies.

What About Grid Charging?

Some batteries can be configured to charge from the grid. This can potentially be useful when electricity prices are lower at certain times. For example:

Cheap electricity → battery → higher-price period

But the economics depend on your tariff and battery system. Solar Victoria confirms that some battery systems can charge from the grid during off-peak periods. The important question is whether your particular battery and electricity plan make this worthwhile.

How Samsun Energy Would Size Your Battery

A good battery assessment should follow the actual energy flow of your home.

Step 1 – Assess Solar

Solar system size, annual generation, seasonal generation, roof orientation, shading, inverter, and existing system performance.

Step 2 – Assess Electricity Use

Annual consumption, daytime consumption, evening consumption, overnight consumption, and seasonal changes.

Step 3 – Assess Solar Exports

How much solar are you currently sending to the grid? This is one of the most useful numbers for battery sizing.

Step 4 – Assess Future Loads

Ask whether you're adding EV, heat pump, air conditioning, pool, electric hot water, induction cooking, home office, or additional occupants.

Step 5 – Model 10kWh

What would the battery actually do?

Step 6 – Model 13.5kWh

What additional energy would it capture?

Step 7 – Model 20kWh

Would the extra capacity actually be used?

Step 8 – Compare Economics

Calculate upfront cost, incentives, annual savings, battery degradation, and expected useful life for realistic ownership economics.

Don't Just Ask for a Battery Quote

Ask for a battery comparison. A good proposal should show something like:

	10kWh	13.5kWh	20kWh
Installed price	$	$$	$$$
Incentive	$	$$	$$$
Net price	$	$$	$$$
Usable capacity	kWh	kWh	kWh
Continuous output	kW	kW	kW
Estimated annual cycles	—	—	—
Estimated annual savings	—	—	—
Estimated payback	—	—	—
Backup	—	—	—
End-of-warranty capacity	—	—	—

That lets you compare value, rather than just capacity.

What Doesn't This Comparison Tell You?

A battery size alone cannot tell you:

Exact annual savings
Exact payback
Blackout runtime
Whether the battery will fully charge every day
Whether your network will approve the connection
Whether your inverter is compatible
Whether your switchboard needs upgrading
How much energy you'll export
Your actual usable capacity
The battery's performance after years of use

That's why 10kWh vs 13.5kWh vs 20kWh is only the beginning of the decision.

A Quick Decision Tree

Do you have moderate evening consumption?

Yes → Start by modelling 10kWh.

Do you have higher evening consumption and a larger solar system?

Yes → Compare 10kWh vs 13.5kWh.

Do you have high evening demand, a large solar system, and future electrification plans?

Yes → Compare 13.5kWh vs 20kWh. A 10kWh battery that is used every day can be more valuable than a 20kWh battery that is rarely filled. Likewise, a 10kWh battery that repeatedly runs out at 7pm may be too small for a high-consumption household. The right battery sits somewhere between those two extremes.

Size the battery around the energy your home can realistically store and use — not the biggest number on the brochure.

Frequently Asked Questions

Is 10kWh enough for a house?

It can be. A 10kWh battery may suit a household with moderate evening electricity use and enough solar surplus to regularly charge the battery. The correct size depends on actual energy consumption and solar generation.

Is 13.5kWh better than 10kWh?

Not automatically. A 13.5kWh battery provides more storage, but the additional capacity only creates additional value if your solar system can charge it and your household can use the stored energy.

Is a 20kWh battery too big for a home?

Not necessarily. It can be appropriate for high-energy homes with large solar systems, high evening consumption, EV charging, electric appliances or significant backup requirements. But it may be unnecessarily large for a moderate household.

How do I know what battery size I need?

Start with three numbers: your solar surplus, your evening/overnight electricity consumption and your future electricity demand. Then compare battery sizes against those numbers.

Does a bigger battery save more money?

Not necessarily. A larger battery costs more and may be under-utilised. Solar Victoria's current guidance notes that battery sizing has a significant effect on payback and that smaller batteries can sometimes have faster payback.

Should I get a 20kWh battery if I have a 13.2kW solar system?

Not automatically. A 13.2kW solar system can provide substantial generation, but your household consumption, solar exports and future loads determine whether 20kWh of storage is justified.

Can I expand my battery later?

Some battery systems are modular and can be expanded, but not all are. Solar Victoria recommends confirming expansion capability with the installer before purchasing.

Does battery size determine blackout runtime?

Only partly. Runtime depends on usable capacity, household load, inverter power and which circuits are backed up. A 20kWh battery does not automatically provide 20 hours of whole-home backup.

Can a battery charge from the grid?

Some systems can. Grid charging can potentially be used during lower-cost periods depending on the battery, inverter and electricity tariff.

What is more important: kWh or kW?

Both. kWh describes stored energy capacity, while kW describes how much power the system can deliver at a given time. For backup and large appliances, inverter power can be particularly important.

Sources & Further Reading

These authoritative resources complement Samsun Energy's practical expertise and help homeowners make informed decisions about the right battery size for their home.

Ready to Find Your Battery Size?

Samsun Energy designs battery storage around the complete energy system rather than choosing capacity in isolation. The assessment can consider solar generation, electricity consumption, solar exports, future EV/heat-pump loads, backup requirements and current incentives — then compare whether 10kWh, 13.5kWh, 20kWh or another size is the better fit.

Get a Battery Assessment Explore Battery Storage

Explore More Resources

Tags:

Author

Samsun Energy

Your email address will not be published. Required fields are marked *

Office Address

Phone Number

Email Address

Blog Details