Solar battery storage is it worth it?
Solar battery storage
A solar battery captures any unused solar power generated during the day, which is then used later at night and low-sunlight days. Solar installations that include batteries are becoming increasingly more popular. There is a real attraction to being independent from the grid: for most buyers it isn’t just an economic decision, but an environmental one. Whilst for some it is an expression of their wish to be independent of energy companies.
If your solar panel array and battery included are large enough, you can run your entire home on solar power. Using the energy from your battery can be cheaper per kWh than using electricity from the grid, depending on the time of day and electricity tariffs in your area.
Grid-connected vs off-grid
There are four main ways your home can be set up for electricity supply.
Grid-connected solar (no solar battery storage)
The most general set-up for homes with solar panels. The solar panels supply power throughout the day, and the home normally uses this power first, and resorting to grid power for any extra electricity needed on low sunlight days, times of high power usage and night.
Grid-connected no solar
The most generic set-up, where all of your electricity comes from the main grid. The home has no solar panels or batteries installed.
This system does not connect to the main grid. All the home’s power comes from solar panels, and possibly some other types of power generation as well e.g. wind. The battery is the main source of power at night and low-sunlight days. The final back-up is usually a dieseled-powered generator, which may also kick in when theres a high demand for power (such as a pool pump starting up).
Off-grid systems generally are much more complex and expensive than grid-connected systems. They need extra solar and battery capacity than your typical grid-connected system and might also need inverters capable of higher loads to deal with peak demands. Homes that are run off-grid need to be particularly energy-efficient and the load demand must be well-managed during the day.
Off-grid systems usually only make sense for remote properties where grid connection isn’t available or would be too expensive to install.
Grid-connected solar + Battery also known as a “Hybrid System”
These have solar panels, a hybrid inverter (or multiple) and a battery, including connection to the main grid. The solar panels supply power throughout the day, and the home generally uses the solar power first, using the excess to charge the battery. During times of high power usage, or night and low sunlight-days, the home draws power from the battery, and as a last resort from the grid.
What happens during a blackout?
For most grid-connected systems, having a battery doesn’t necessarily protect you during a blackout. You can still lose all power to your home, despite having solar panels producing power and a charged battery waiting. This is due to grid-connected systems having a “anta-islanding protection”. During the course of a blackout, the grid and the engineers working on the lines have to be protected from “islands” of electricity generation e.g. you solar panels, pumping power unexpectedly into the lines. for most solar PV systems, the simplest way to provide anti-islanding protection is to completely shut down. When the grid senses a grid blackout, your solar PV system shuts down and you have no household power.
However, more sophisticated inverters provide anti-islanding protection during the course of a blackout, but still keep solar panels and batteries operating leaving the house with some power. You can expect to pay a bit more for a system like this, as the hardware is more expensive and you may need more battery and solar capacity than you think to run the house during a blackout. You may also choose to only allow critical household circuits to operate in this situation, such as the fridge and lighting.
Below are the key specifications for a home battery.
How much energy the battery can store, this is usually measured in (kWh) kilowatt-hours. The nominal capacity is the total amount of energy the battery can hold; the usable capacity is how much of that can actually be used, after the depth of discharge has been factored in.
DoD (depth of discharge)
Expressed as a percentage, this is the amount of energy that can be safely used without accelerating battery degradation. Most batteries need to hold some charge at all times to avoid any damage. Lithium batteries can be safely discharged to about 80-90% of their usual capacity. Lead-acid batteries can usually be discharged to 50-60%, whilst flow batteries can be full discharged at 100%.
How much power in kW (kilowatts) the battery can deliver. The maximum power is the most the battery can deliver at any moment, but this burst of power can usually only be sustained through short periods. Continuous power is the amount of power delivered while the battery has enough charge.
For every kWh of charge put in, how much the battery will actually store and put out again. There is always some loss, but a lithium battery should usually be more than 90% efficient.
Total number of charge/discharge cycles
This is how many cycles of charge and discharge the battery can perform before it is considered to reach the end of its life. Lithium batteries can usually last for several thousand cycles.
Years of cycles
The expected life of a lithium battery can be rated in cycles. The lifespan should also state the expected level of capacity at the end of life; for lithium batteries this will usually be about 60-80% of the original capacity.
Ambient temperature range
Batteries are sensitive to temperature and need to operate within a certain range. They can degrade or shut down in very cold or hot conditions.
Types of battery
The most common type of battery being installed in homes, these batteries use similar technology to their smaller counterparts in laptop computers and smartphones. There are multiple types of lithium-ion chemistry. A common type that is used in home batteries is lithium-nickel-manganese-cobalt (NMC), used by LG Chem and Tesla.
- They can give several thousand charge-discharge cycles
- They’re suitable for a wide range of ambient temperatures
- They can be discharged heavily (80-90% of their overall capacity)
- They should last for 10+ years in normal use
- End of life may be an issue for large lithium batteries
- The batteries need to be recycled to recover valuable metals and prevent toxic landfill, but large-scale programs are still in their infancy. As home and automative lithium batteries become more common, it’s expected that recycling processes will improve.
Lead-acid, advanced lead-acid (lead carbon)
The lead-acid battery technology that helps start your car is also used for larger-scale storage. It’s a well-understood and an effective battery type. However, without a significant development in performance or reduction in price, it’s hard to see lead-acid competing long-term with lithium-ion or other technologies.
- Established disposal and recycling processes, whilst also being relatively cheap
- Sensitive high ambient temperatures, which can shorten their lifespan
- They have a slow charge cycle
One of the best alternatives to lithium-ion, this type uses a pumped electrolyte (such as zinc bromide or vanadium ions) and chemical reactions to store charge and release it again. However, this is currently unavailable in Australia.
- They can be discharged to 100% of their capacity with no residual discharge meaning they won’t lose charge over time
- Operate well in high ambient temperatures
- Easy to recycle
- Should last for 10+ years
- As they’re new technology, they are more expensive than lithium-ion
- Don’t tolerate cold that well (below 15°C)
- Require frequent maintenance
Other types available
Battery and storage technology is in a state of development. Other technologies currently available include the Aquion hybrid ion (salt water) battery, molten salt batteries, and the recently announced Arvio Sirius supercapacitor.
How long do solar batteries last?
Most solar batteries should be able to last 10 years or more under normal usage and not put through extreme climates (temperatures). Most batteries have a 10 year warranty, and should be able to outlast that.
Are solar batteries worth it?
Many people are investing in home battery storage, or at least ensuring their solar PV systems are battery-ready. The price of solar batteries continues to drop, and is becoming a more popular investment for home owners. We recommend that you ensure your battery has a 10 year warranty, and we will ensure you have continuous support along the way.
Rebates, subsidies and virtual power plants
Currently in Western Australia we do not have any rebate schemes for battery systems. We will continue to update this as more information becomes available.
When you’re adding up whether a battery makes sense for your home, remember to include the feed-in tariff. This is the amount you are paid for any excess power generated by your solar panels which is then fed into the grid. Every kWh diverted instead into charging your battery, you’ll forgo the feed-in tariff. This should be considered as an opportunity cost when installing your system.
Solar battery storage costs
Costs vary significantly for solar batteries, however, the higher the capacity of the battery the higher the cost usually is.
Below are some typical battery costs for common capacity sizes which covers just the battery. Installation will include an additional cost.
- 6kWh: $4,000 – $9,600
- 10kWh: $7,600 – $13,500
- 13kWh: $9,600 – $15,000
Generally you will need to add the cost of a new inverter and extra cabling for connection. It can be more cost-effective to buy a battery as part of a brand new solar panel system than to fir it it to an existing one.
Your home insurance
Your solar system (battery, inverter, panels) are part of your house, meaning it is covered by your home insurance. However, you should make sure your home’s insured amount is increased to cover replacement costs of the solar system.
At Westsun Solar we have over 10 years experience in the solar industry. To find out more about solar battery storage feel free to contact us with any questions or queries. Our team of professionals will be more than happy to help you find the solution you are looking for.