Choosing The Right Battery

Choosing a battery for your home

Although installing different types battery technology is still possible for your home, the many advantages of lithium battery technologies coupled with the reductions in price have seen them dominate the residential battery market. It is for this reason This page will concentrate on  lithium battery technologies.

For more information on some of  the different battery types see our page battery types  

How will a battery in the home benefit me?

A battery can provide power backup when there is  a blackout ?

For this application we need to know how long the power is generally off for and how frequent the blackouts. Then we need to know what appliances you intend to be using throughout this time. From this we can calculate your peak current and total kWh requirements and select a battery to suit.

The maths are below are simplified (for estimation only**):

I have an average of two blackouts a week for around 1 hour each time while the power is off I use my air conditioner that draws 1kW and my cool room draws 1kW also. there have never been two power outages on the same day but that’s not to say it won’t happen I want to be prepared. well 1kW A/C + 1Kw Cool room = 2kW for 1 hour so 2kWh required. The customer specified that they want to be prepared in case 2 blackouts occur in one 24hr period so 2kWh  x 2 = 4kWh battery is required for this task.

A battery can save money on a split tariff bill.

For customers that are already on or have the option to change to a split tariff bill, they would charge the battery at the cheap (off-peak) price sometimes around 12c/kWh and use it when the price is higher sometimes around 50c/kWh

The maths are below are simplified (for estimation only**):

One example is the above split tariff and a usable 10 kWh in battery storage.

So for each kWh that you use you save 38c then 38c x 10 kWh is $3.80 per day multiply that by 365 days in the year and x 10 years which is the warranty period of this battery and you get $13 870 saved from your bill. if this figure is close to or greater than the cost of the battery installation then this may be a good idea. A more thorough set of calculations need to take place to assess your suitability for a battery installation.

With Solar Panels you can store the excess solar power in batteries to use at night?

If so we need to know how much unused solar power you generate each day.  Then we need to know what appliances you intend to be using throughout this time. From this we can calculate your peak current and total kWh requirements and select a battery to suit.

­­­

The maths are below are simplified (for estimation only**):

A Customer has a solar installation that produces an excess of 10kWh  even on its lowest performing day he lives in a rural location with no feed in tariff

During the night the customer has a cool room running that uses a total of 4kWh as well as this the TV’s and computers and fridges use a further 2kWh and finally the lights use 0.5kwH so

4kWh Cool room + 2kWh TV and Computer and fridges + 0.5kWh lighting = 6.5kWh min battery size required for this task.

The customer will save 6.5kWh each day at 25.75c by 365 days for 10 years = $6109.19 if this figure is close to or greater than the cost of the battery installation then this may be a good idea. A more thorough set of calculations need to take place to assess your suitability for a battery.

Feel free to use this information to see if your cost vs. return reasons = good idea to buy or not, but be sure to base your final choice on further professional calculation and design.

That being said some customers are purchasing battery systems just for the reassurance of uninterrupted power.

For some customers the power going off during just one important football match was enough motivation to get a  battery installed so it would never happen again

Batteries used for Backup or Uninterrupted Power Supplies: They are not all the same !

UPS (Uninterrupted Power Supply) for selected circuits or the whole installation

Do you run a server or have medical equipment that needs uninterrupted power.

If this is the case then this is a very important question to ask your battery retailer. The different technologies in inverters and also the different ways that they can be installed will affect how they will operate in the case of a power outage. uninterrupted power supply is not offered by all. You need to be clear of your requirements so you can select the right battery and inverter combination to suit your needs. Some of the more common features are explained below.

Nominated backup for Selected Circuits or outlets.

When the power goes out then one or two predetermined circuits will either have backup power after a brief interruption or an uninterrupted power supply  depending on the inverter selected and the way it is installed.

Backup power for the whole installation.

When the power goes out the whole electrical installation will either have backup power after a brief interruption or an uninterrupted power supply would provide a seamless transition from grid to battery and back to grid again depending on the inverter selected and the way it is installed

Do your solar panels charge your batteries while the power is out?

At first this sounds like a silly question but if you’re using a standard grid tied solar inverter then as a requirement it shuts down when the grid power is down so no charging your battery or assisting it with the load at this time. There are many different combinations of technology that do allow the solar to work with the grid down you just need to discuss that with your solar retailer as I have already mentioned it depends on the inverter selected and the way it is installed

** Please Note: There are many considerations to be taken into the full calculations.

• You will save less money on each day the batteries cannot fully charge up. This can be mitigated with further investigation and a possible increase in solar array size.
• The cost of electricity is likely to rise leading to bigger savings.
• The 7.135c that some electricity retailers pay for electricity sold back to the grid may go down up or disappear altogether there is no guarantee.
• Some areas do not have feed in tariff’s at all.
• Cost of electricity varies wildly per kWh throughout Australia you need to know your tariff’s.
• The total storage capacity of the batteries diminishes at a set rate over time, this needs to be accounted for.
• As well as other general considerations are also brand and model specific limitations that need to be taken into account.

WE at Northern Perth Electrical would be happy to help you decide if a battery with or without solar power is right for your situation. Give us a call or send us an email and we will arrange a suitable time to discuss your options.