Home battery storage

By Mozo ·

According to the Clean Energy Council, more than 2 million Australian households use solar energy to power their homes. And as renewable energy continues to grow in popularity, it’s almost certain the number of solar installations is also set to climb. 

In addition to solar panels, home battery storage can also work to delivery energy savings, reduce dependency on the grid and provide a sustainable solution to where Australian households source their power. 

If you’ve been thinking about making the switch over to solar power, here’s what installing a home battery system could mean for your energy bills. 

What is home battery storage?

To answer this, we’ll need to start from the top. We all know that solar power is generated by converting the sun’s rays into electricity, which can power all kinds of household appliances, from the kettle to heating up water. Any ‘excess’ generated electricity is then fed back into the grid and households are paid a fee for their contribution, called a feed-in tariff.

But what if it was possible for household’s to use every bit of electricity their panels generated? Enter home battery storage systems. Just like you’d use a battery to store electricity for your laptop or smartphone, a home battery stores excess sunlight before converting it into electricity that can be used whenever needed. 

What does home battery storage consist of?

There are three parts that make a typical home battery storage system, they are:

  • Solar panels: These are responsible for converting sunlight into electricity. The size of your system varies depending on factors, like the number of people in your household and the structure of your home. You can check out our solar panels FAQ guide for more information. 

  • Home battery: A home battery stores excess electricity generated from solar panels so that it can be used when generation is not at its highest, like during the night.

    Inverters: Electricity generated by solar panels is known as a ‘direct current’ (DC), while household appliances require an alternating current (AC) to function. Inverters, which are connected to both your solar panels and home battery, work to convert the DC electricity into AC.

What are the benefits of home battery storage?

Together with rooftop solar system, battery storage presents a huge opportunity for Australian homes to use a larger percentage of the solar power they generate at home and minimise the need to purchase expensive electricity from the grid. Advantages of home battery storage include: 

Lower bills:

Since many homes use the bulk of their energy at night, a battery storage system will power the house after the sun goes down reducing your dependency on the electricity from the local grid, therefore lowering your bills. 

Green power:

Apart from saving you money, battery storage is also good for the environment because it uses solar energy. Also, with the upfront cost for solar systems dipping over time, more people will be encouraged to adopt sustainable energy solutions.

Blackout support:

A battery storage system should be able to keep some of your home’s appliances running for a number of hours even when the power is out. 

Battery sizes and specifications

When choosing a home battery, there are a number of things to get your head around. While it may seem that the size or total capacity of the battery is the most important feature, a number of other interdependent factors determine how much power can actually be used at a given time and how your battery will perform in the long run. Some of the important aspects to consider include: 

Capacity

A battery’s capacity is how much electricity can be produced over a period of time - usually measured in kilowatt hours (kWh). The capacity of your battery should relate to the capacity of your solar system and the amount of excess energy you are able to send back to the grid. For example, say your solar export is between 6 kWh and 9kWh in a day, you can consider a battery with a 7 kWh capacity and if your solar export is between 9 kWh and 15 kWh in a day, you can consider a battery with a capacity of about 11 kWh. 


Depth of Discharge (DoD)

This is an important feature of a home battery. DoD is what tells us what percentage of the battery capacity has been used up. For instance, if a 10kWh nominal capacity battery has only 2kWh stored in it, then its current DoD is 80%. While a battery bank may have a capacity of 10kWh, that doesn’t necessarily mean it can store a useable 10kWh of energy. DoD limitations could mean it may only be possible to access 5kWh or 50% DoD. 

The higher the DoD, the more battery capacity you can use before recharging is required. While you can use up all the energy stored in the battery, discharging batteries too deeply can significantly reduce the value that they provide over their lifetime. 

Cycle life of a battery

The cycle life of a battery is the number of complete charge/discharge cycles that the battery is able to support. Each battery manufacturer will class its batteries as having a set cycle life at a specified average depth of discharge (DoD): for example, 3,000 cycles at 40% DoD. 

Round trip efficiency

When you store energy in a battery, some of it is lost due to heat or other inefficiencies. Round-trip efficiency can be defined as how much energy is lost in a “round trip” between the time the energy storage system is charged and then discharged. Say, if 1kWh of electricity is fed into a battery and the amount of energy which can be extracted from that input is only 800Wh then the efficiency of the battery is 80%. 

What is the lifespan of a solar battery?

Solar batteries can typically last between 5 to 15 years, however it will depend on how you look after it. For instance, you’ll need to protect your battery from both incredibly hot and cold temperatures. In drastically cold temperatures, your battery will need more voltage to fully charge, while in sweltering conditions, the voltage will need to be reduced to avoid overheating.

How long does a solar battery take to fully charge?

This will depend on the size of the battery, but generally, solar batteries take up to 8 hours to fully charge. A great way to effectively charge your battery is to make sure your panels are in the best position, pointing toward the sun.

Who offers battery storage in Australia?

As more households opt for solar power, product availability improves. While solar panels are available through accredited installers, there is more flexibility in where you can purchase your battery - you might even be able to pick one up through your retailer! Some examples of where you can purchase home solar batteries are:

Tesla Powerwall

Tesla, which made its name in electric cars has launched Tesla Energy here in Australia. Powerwall is a wall mounted, rechargeable lithium ion battery with liquid thermal control and comes in 10 kWh and 7 kWh models. It comes with a 92% round-trip DC efficiency and is expected to cost around $3800 for 7 kWh and $4435 for 10 kWh. The Powerwall is expected to start shipping in late 2015. The system can be reserved via the Tesla website and must be installed by a trained technician. 

AGL Power Advantage

AGL was the first major energy retailer to announce it was launching a battery storage device for the Australian market. AGL’s Power Advantage lets you choose from three different battery sizes (7.2kWh, 11.6 kWh and 19.4kWh) to fit with your existing solar system, or with a new installation. 

The Power Advantage range comes with an inverter and all installation costs included. It is compatible with solar PV systems from 3kW to more than 5kW in size. The three sizes are priced at $9,990, $14,990 and $19,990 respectively and come with a 10-year warranty. While the DoD for the 7.2kWh battery is 90% for the other two it is 80%. If you are interested in AGL’s solution you can register for further updates.

Origin Batteries

Origin Energy have two solar battery options available: the Tesla Powerwall 2 and LG Chem Resu. The Tesla battery option offers a 13.5kWh capacity and can be added to an existing solar system or be included in a new system. Prices for this model start at $14,995. With the LG Chem Resu, households have a choice between 6kWh and 10kWh capacity, both of which come with a 5-year warranty. Prices start from $10,795. 

Enphase

Enphase are a global energy innovator who aim to make solar power simple, efficient and effective. The Enphase AC battery has a capacity of 1.2kWh and an impressive 100% DoD and minimum 10-year life expectancy. According to Enphase, their simple installation process also helps keep costs low. Battery Storage payback period

According to a Climate Council report, in Australia, most solar PV systems ‘pay for themselves’ in less than a decade. Other studies (Commonwealth of Australia 2014; ESAA 2015) have estimated solar PV systems pay for themselves between 4 to 12
years, with the shortest payback periods in the Northern Territory or South Australia.

Are home battery storage systems worth it?

Switching to solar power is a massive financial investment for any Aussie household, so it’s not uncommon for many solar customers to wonder how long it will take for the potential savings to cover the upfront costs. This is commonly referred to as the ‘payback period’. 

According to Zen Energy, an Australian solar energy and battery storage company, “a well-designed solar battery storage system that is combined with a new solar system typically takes around 6 to 12 years to payback”. 

Home battery storage to overtake feed-in tariffs incentive 

When feed-in tariffs were quite generous, Australian households with solar PV had greater incentive to feed as much electricity into the grid as possible. But as these feed-in tariff schemes have been scaled back or stopped in recent years, the incentive is also steadily dropping. 

For instance, a typical house in Victoria earns 6.2c/kWh for solar power fed into the grid, (dropping to 5c/kWh in 2016), but are paying a much higher price to buy electricity from the grid (typically around 33c/kWh) when the sun is not supplying the solar panels with any energy.

As feed-in tariffs are phased out and electricity prices increase (particularly at peak times), solar PV systems with added battery storage will become the most economical solution to meet household electricity needs.

You can read more on how solar energy or renewable energy works by checking out our handy range of energy guides!

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