The million dollar question recently has been “what about batteries?”

We’ve all heard that the Tesla Powerwall battery storage for solar is coming to Australia. Here’s a basic explanation of what these Lithium ion batteries mean for your average Australian home

Why is it revolutionary?

Battery storage to complement a solar PV system has existed for some time but would involve lead-acid batteries. Lead acid batteries need regular maintenance, are very large and heavy, emit hydrogen gas and have to be replaced approximately every 5 years. The new lithium ion batteries are lighter, low maintenance, don’t emit hydrogen gas and are guaranteed for up to ten years with a life expectancy of around 10-15 years.

The advantage of having battery storage is that you can store the power when it is generated (when the sun is shining) and use it when your panels are not generating electricity (eg after dark).

Great, so that means I should get them?

Well, in the same way that the Tesla car is very desirable and now available it’s price of over $130,000 means that we can’t all rush out and buy one! For most of us in-home battery storage system is still prohibitively expensive. When adding the panels, the inverter, the batteries and all the components for a 5kW system (which would probably be sufficient for a fairly energy conscious Melbourne family home that remains connected to the grid but wants the benefit of being able to store solar power that is not used during the day) you’d be looking at paying around $18,000-$25,000 to set up a system with battery storage. The return on investment would be around 12-14 years and the batteries are usually guaranteed for 10 years, so financially batteries don’t yet stack up. However, the fact that the technology is now readily available hopefully means that more companies will develop similar systems (which seems to be happening already), creating a competitive and more affordable market.

But I already have solar PV and an inverter, so can’t I just add batteries?

Although possible it is not that simple. Most existing inverters are not ‘battery ready’. This is mainly due to the fact that your inverter is designed to convert the DC power from your panels, into AC power, which your home can use. So to add batteries you would essentially have to add another inverter to convert the power back to DC to charge the battery from the house. This would mean a large cost increase and also means some loss in efficiency by the time the power has been converted from DC to AC and back again. A ‘battery ready’system would allow the battery to be charged directly from the panels or for the power to go into the house. Some systems will do this automatically, while some can be programmed or manually set to send then power either to the home or the battery depending on when you need the power.

Hopefully soon a ‘bolt on’ battery back-up system will come on the market but at the moment it is worth considering buying a new ‘battery ready’ inverter.

But I’ve already got the panels, so that must save me some money?

True. And in most cases when you do add on battery storage you will not need to replace your panels. However your panels
themselves are not really the bulk of the cost of a system. Your inverter and the labour involved in installing it (electricians are highly skilled and risk their lives, so they charge accordingly) are.

What do you mean ‘in most cases you won’t need to replace panels’?

For those of you who were early adopters let us first say well done! And hopefully you have been receiving the premium feed in tariff and reaping the benefits. Although your panels should still be working fine the rules and regulations have changed, so you may find that some of your wiring and panels no longer meet requirements. Please also note that if you make any adjustments to your existing system you will lose the premium feed in tariff.

So I should hold off getting solar until I can get the full package?

It is entirely up to you. However we firmly believe that it is worth getting solar as soon as you can. You will start saving on your bill and adding more renewable energy into the power supply. If you get the system size right for your energy usage then your system should pay for itself in savings within 3-6 years. So if you are going to be looking at adding a battery back-up system in 3 or more years then it is still well worth getting solar now. All being well the technology will quickly come on the market that can be added to your system, so you won’t need to start again.

If I get batteries will I be able to go off grid?

If you are setting up an off grid system for example on a rural property, then the financial case for getting solar and batteries or your system is strong. Traditionally these sorts of systems would have had a back up generator, which can be high maintenance, expensive to run and usually run on diesel, which emits nasty fumes. However if you are installing solar and batteries to a grid (mains) connected house then it is not really worth your while installing solar and batteries to go off grid, as you would need a large battery bank to get you through several cloudy days in winter and during summer days you would be generating far more electricity than you need. The batteries will be expensive and will need quite a lot of space to be stored in. By staying grid connected excess power is not wasted (because it is fed back to the grid) and you will always have the ability to buy power from the grid when you are not either generating power or are using stored power. By staying grid connected you are adding renewable energy to the mains supply. Most grid connected systems are set up to maximise the power you can use from your solar but are not set up to allow you to get all your power from your solar year round.

If I get batteries will I still have power in a power outage

Most grid connected solar and battery systems will cut out in a power outage, in order to keep people working on the lines safe. Some systems will have the option to switch off from the grid and only use your solar and batteries. There are already a lot of different options available, so you can discuss these when getting quotes.

If you are already off grid then power outages won’t make a difference to your power supply.

Read more on battery storage in our latest news section here, and here.