Battery Storage for Solar Power Systems

With a battery storage system, you can use your free solar power during the day, then draw down on your excess solar energy from your battery bank at night. Energy independence!

Jump To

Why Use Battery Storage

Who doesn’t want a nil bill? Households and businesses alike want to be more self-sufficient and less reliant on the grid by storing clean energy generated by their solar panels.

At the moment, the greatest shortcoming of solar power is that you need to use your solar energy at the time that it’s produced to get the greatest benefit. Not everybody can take full advantage of their solar panels’ output. For example, a typical working family which has higher usage early in the morning and in the late afternoon/evening, as the graph below demonstrates:

This is where battery storage comes in.

There are 3 main reasons you’ll want to add batteries to a grid-connected solar power system:

  1. you want to store the excess energy that your solar power system generates during the day and then use this at night when your panels aren’t working.
  2. you want to have backup power available if the grid goes down (mostly applicable in regional areas).
  3. you’re tired of electricity tariff increases and want to cut the cord to the grid and never pay an electricity bill again.

If you’re unsure of the critical questions to ask when it comes to choosing and installing a battery, here’s our Battery Storage Buying Guide with the Top Ten Questions You Need To Ask.

Household Power Consumption

How Does a Battery Storage System Work

Here’s an example of how a system with a SolarEdge battery storage technology works.

Here’s an example of how a system with a Tesla Powerwall battery storage system works:

  • your solar panels convert sunlight to DC electricity (Direct Current).
  • any surplus DC electricity that your home or business doesn’t use charges the Tesla Powerwall.
  • the inverter converts the DC electricity to AC (Alternating Current) for use in the home or business.
  • a special type of inverter also converts AC to DC to charge the PowerWall.
Battery Storage System Layout

With batteries, both your daytime and evening electricity usage is free because:

  • any appliances that have run during the day can run at zero cost direct from the solar panels; and
  • many appliances that run of an evening can also run for free, drawing your stored solar energy from your batteries

How Much Energy Can Batteries Store?

This depends on the brand of batteries that you buy, but most household battery storage units are capable of storing between 3.2kWh and 10kWh. When you use up the storage capacity of your batteries of an evening, you simply draw any remaining power from the grid.

Can I Disconnect From the Grid If I Get Batteries?

Although we all like the idea of disconnecting from the grid altogether, for most households and businesses, it’s advisable to stay connected. This is because the cost of a hybrid system (where you have solar panels + battery storage + the grid as your backup) is so much cheaper than an off-grid system.

The cost of an off-grid or stand-alone system is about $50,000. If you’d like us to design an off-grid system for you, our accredited designers can do this for you. Just complete this Load Assessment Worksheet as thoroughly as you can and email it across to us.

What’s The Difference Between Hybrid and Off-Grid Battery Storage?

With a hybrid battery solution, you remain connected to the grid. You use your solar panels during the day, draw down from your battery system overnight and have the grid as your backup if your panels and batteries don’t provides sufficient power to cover your consumption. 95% of customers in metropolitan areas will opt for this solution because hybrid systems are so much cheaper than off-grid systems.

As the name suggests, with off-grid systems, you are not connected to the grid. You use your solar panels during the day, draw down on your (larger) battery system when required and usually have a diesel or petrol generator as your backup.

You can choose to go completely off–grid (usually a minimum of $50,000), but this is only really advisable if:

  • you’re building a new house and it’s going to cost you as much or more to install poles and wires to your house as it is to install an off-grid system; or
  • you get regular blackouts and/or brownouts
  • you want to be 100% self-sufficient as far as your energy needs are concerned

What Are The Different Kinds Of Battery Storage Solutions Available?

There are many different kinds of batteries now available, but the 2 main types used in residential and commercial environments are lithium-ion and lead acid:

Lead acid batteries are the way to go if:

  • you have ample storage space to accommodate the batteries
  • you want an energy storage solution with a relatively low upfront cost
  • you want a technology that’s widely used and well-established

Lithium-ion is the go-to energy storage solution if:

  • you want/need a relatively large amount of power instantaneously
  • you’re prepared to invest a bit more money
  • you want a longer life-cycle and a deeper discharge rate

Pros and Cons of Lithium-Ion Batteries

LITHIUM-ION – If you want battery storage that can provide an immediate and relatively large amount of power (and you’re prepared to invest a bit more money in your battery solution), lithium-ion is the go-to energy storage solution. The leading lithium-ion battery brands are currently LG Chem, Tesla and Samsung.


  • This type of battery lasts longer, greater cycle life: 3000-5000 cycles (in other words, 3000-5000 days of storage if cycled once a day).
  • Latest technology
  • Decent storage capacity e.g. 6.4kWh-10kWh
  • Scalable – you can easily add to it
  • Lighter
  • Great for retrofits
  • You can discharge lithium-ion batteries more than lead acid (80% of their rated kWh capacity, compared to around 30% with lead acid) without significantly damaging their ability to hold a charge
  • You can manage the batteries online so that your household automatically tops itself up from the grid if required
  • Lower maintenance


  • Potentially dangerous if poorly installed (runs at very high voltage and the electrolyte is highly combustible)
  • Poor recyclability
  • Generally has to be located indoors or in a weatherproof ventilated enclosure; can’t be located in a habitable room.
  • More expensive than lead acid

Lithium-ion overview:

  • Cycle life: Up to 8,000 @ 80% DoD (depending on type)
  • Lifespan: Up to 12 years
  • Recommended depth of discharge: up to 80% (depending on type)

Pros and Cons of  Lead Acid Batteries

If you want an energy storage solution with a relatively low upfront cost that’s widely used and well-established, lead acid batteries are the way to go.

The leading lead acid battery brands are currently Selectronics and Ecoult.


  • Longer lifespan; designed to work in partial state of charge (ie. discharged and charged more than lithium-ion).
  • Proven technology: lead acid batteries have been in widespread commercial use longer than any other battery type
  • High recyclability
  • Weatherproof; can be positioned outdoors; doesn’t have to be mounted on a wall
  • Scalable – you can easily add more storage capacity down the track
  • You can manage the batteries online so that your household automatically tops itself up from the grid if required
  • Cheaper
  • Safe to install/use


  • Fewer cycles than lithium-ion
  • Can’t be discharged as deeply as other battery types without damaging their ability to hold a charge
  • They’re big: lots of space required
  • They have a relatively short cycle life

Lead acid overview:

  • Cycle life: 800-5,600 @ 30% DoD (depending on type)
  • Lifespan:Up to 12 years
  • Recommended depth of discharge*: usually 30%

* Depth of discharge = the degree that a battery is emptied relative to its total capacity. For example, if you have a battery bank with a capacity of 10kWh, at 70% DoD, for example, that battery bank has 3kWh of charge remaining, which will not be used.

What Size Battery Storage System Do I Need?

For most households, 5–10kWh of storage is ample for evening/overnight use.

If you can skew your energy consumption so that you’re using the bulk of your total energy during daylight hours you’ll only need a 3kW – 6.5kWh battery storage unit. This is because you’ll be able to run your heavy duty appliances directly from your solar panels during the day for free and just use your battery bank to power your fridge, lights, TV, standby power and computers at night.

If more of your usage is of an evening, then a larger battery storage unit (10kWh) would be advisable.

If you’re not sure how much of your overall consumption is during the day vs late afternoon/overnight, you can work out your energy usage profile a number of different ways:

  • the cheapest way of doing this (in fact, it’s free) is to take a note of your meter reading in the morning (eg. 8am) and again late in the afternoon (eg. 5pm) for a number of days. This will tell you how much energy you’re consuming during daylight hours vs overnight
  • if you want to get really specific about your energy usage profile, contact us and we can organise for interval data to be measured in real time over a week-long period. This will tell us how much energy you’re using in 15 minute increments.

How Much Energy Can You Save With A Battery System?

  • You can reduce your reliance on the grid by 80-90% with a solar + hybrid battery system.
  • You can reduce your reliance on the grid by 100% with an off-grid battery system.

In order to do this accurately, we recommend a Free Home Assessment or Free Business Assessment.

How Much Do Battery Storage Systems Cost?

The cost of energy independence has dropped over the last 12 months. Lithium-ion systems start from $9,800 for 6.5kWh of storage (eg. LG Chem) and cost around $13,900 for 14kWh of storage (eg. Tesla Powerwall 2).

Your usage System size GOLD system
Expected savings
over 10 yrs*
Return on
Small user
8kW system $8,800 $34,000 2.7 years*
Medium user
10kW system $10,200 $42,700 2.3 years*
Large user
20kW system $16,400 $85,400 1.9 years*
XL user
50kW system $35,100 $213,500 1.6 years*

* Assumes tariff is 30c/kW inc GST; 100% of electricity produced will be self-consumed; panels will degrade at .025% p.a.
Systems above 30kW require a DA, Engineers Report and Grid Protection (total approximate cost: $9,500).

Off-grid systems using lead acid batteries start from $45,000 for 16-17kWh of usable storage.

You can hasten the payback period of your battery by installing a clever Australian-made technology called Reposit Power. It’s a simple-to-use energy trading system that allows you to charge your battery for free or at cheap rates and on-sell your power to the grid for a profit at peak times. It’s like a smart meter that works for you. Take a look at the video below to see how Reposit is working for one of our customers, based in the Northern Illawarra:

Who Should I Choose To Install My Battery Storage System?

More important than the quality of the components you choose is the quality of the installation, as batteries – especially lithium-ion – are highly combustible. It’s imperative to have your battery system installed by a professional who is highly experienced (ideally an accredited off-grid installer who has been installing systems for at least 3–5 years).

Battery Storage Quotes

The Energy Experts fast-track the quoting process for you by sourcing multiple competitive quotes on your behalf from local, professional battery storage installation companies. We’ve cherry picked solar + battery installers in your area that have a reputation for excellence and who are very competitively priced.

Need More Help Finding the Right Battery Storage System

Contact The Energy Experts on 1300 516 474 to receive a free quote/initial consultation about battery storage systems.

Although our home base is in the Illawarra, we have reputable and experienced installers across the state, from the NSW South Coast (Tura Beach; Narooma; Ulladulla) to the Shoalhaven (Nowra), Southern Highlands (Bowral), Sutherland Shire (Greenhills Beach), Sydney (Gladesville; Auburn; Minto; Smeaton Grange), the ACT (Canberra), the Central Coast (Tuggerah), Newcastle (Warabrook) and the North West Slopes (Moree), New England (Glen Innes), the Blue Mountains (Katoomba) and the Central Tablelands (Oberon) regions.