In this video, Finn discusses the different types of home solar battery backup and what happens with each in a mains grid blackout scenario.
In the last video I went through the economics of batteries versus solar power. Batteries do not pay for themselves before the warranty is up at the moment â€“ theyâ€™re not an economically rational purchase in Australia.
But what if you want the other benefits of batteries â€“ and one of the big benefits is backup. What is that worth to you? Well, everyoneâ€™s different and you have to put your own price on it.
Iâ€™ve got a battery in my house and a few months ago the street was totally blacked out. I was cycling home and this is what I saw.
Mine was the only house in the street that had its lights on and life carried on as normal for us for about two or three hours. It was awesome.
So whatâ€™s that worth to you? Only you can decide, but if you do choose to buy a battery for the backup capability, itâ€™s really important that you get the right kind of backup. There are four levels of backup â€“ the following is terminology weâ€™ve invented at SolarQuotes to show you how different the levels of backup power are in the batteries on the market in Australia today.
Letâ€™s start with level zero. Level zero means you donâ€™t actually get any backup. If the grid goes down, your battery stops working. There are plenty of batteries available that do that, believe it or not â€“ avoid those batteries.
Then thereâ€™s level one backup. These batteries will back up your home when the grid goes down, but they will reduce their output power. You might have a five kilowatt battery, so that is a battery that stores energy but its power rating is five kilowatts. When the grid goes down, it reduces its power to say 1.82 kilowatts. Thatâ€™s not a lot for powering your home, so itâ€™s a degraded performance when the grid goes down. Avoid those batteries.
Then youâ€™ve got level two backup. The grid goes down and your battery can pump out electricity at five kilowatts. It is the same power whether itâ€™s in backup mode or itâ€™s in grid-connected mode. I think you should avoid Level 2 as well and thereâ€™s a reason for that â€“ they will not charge your batteries from the solar panels when the gridâ€™s down.
Why wonâ€™t they do that? Because it takes extra electronics to do so.Â Say your solar power system is generating four kilowatts and the grid is not connected. Your house is using two kilowatts. Your battery is full, youâ€™ve got an extra two kilowatts of solar power. Itâ€™s got nowhere to go because the grid is not connected. That means somethingâ€™s going to catch fire or go bang unless you throttle back the solar panels.
So you need extra electronics to throttle back the solar panels. If you want to charge your batteries from solar without the grid, thatâ€™s what we call level three backup. I call it apocalypse-proof backup, because in theory, if youâ€™re careful with your electricity usage, you can go almost indefinitely on battery backup because the batteries will charge up from the solar panels1 as soon as the sun comes up.
If you havenâ€™t got level three backup, once your batteryâ€™s flat and youâ€™re not connected to the grid youâ€™re out of power. So, if youâ€™re going to spend thousands of dollars on a solar battery, get level three backup. To make sure youâ€™ve got level three backup, here is what you say to the person selling you the solar.
â€śI want the solar panels to charge my battery when the gridâ€™s down.â€ť
â€¦ and you get them to write that on the quote.
IfÂ youâ€™re considering buying solar power and/or energy storage, check out Finnâ€™s book â€“ The Good Solar Guide â€“ which is free to read online.