When we talk about energy efficiency at home, we usually mean things like insulation, glazing and efficient appliances. A battery is different. It doesn't make your home more efficient in the traditional sense. It changes what happens to the energy your home produces.
That's becoming more relevant as the federal government's Home Energy Rating scheme has been extended to existing homes, with solar and batteries among the things considered as part of a home's rating.
What the Home Energy Rating scheme covers
The Nationwide House Energy Rating Scheme, or NatHERS, has been used to rate new homes for more than 30 years. The existing homes scheme now gives households a way to assess the energy performance of a home that's already been built.
A Home Energy Rating looks at the home's design and construction, insulation, windows, shading, fixed appliances, solar and battery storage, as well as the local climate. The assessment produces both a Home Energy Rating, scored from 0-100+, and a separate Star Rating out of 10 that measures the performance of the building itself.
The rating is designed to help households understand where energy is being used and which upgrades could make the biggest difference to running costs and comfort.
It can also help inform decisions around upgrades, renovations, selling or renting a property, and accessing government rebates or low-interest loans.
Where a battery fits in
A battery is one of the upgrades that can be recognised in a Home Energy Rating, alongside things like solar panels and efficient appliances.
The reason is straightforward: a battery lets a home use more of the solar energy it generates instead of exporting it to the grid and buying electricity back later.
But there's a limitation to looking at the battery alone. The rating can account for the battery installed at the home, but it doesn't tell you how that battery is being operated day to day.
Two identical batteries can deliver very different results depending on the electricity plan they're connected to and how they're being used.
The plan matters too
Most home batteries are set up to maximise self-consumption. Solar charges the battery during the day, then the home uses that stored energy at night rather than buying from the grid.
That's useful, but it doesn't take the wholesale electricity market into account. Electricity prices can be close to zero in the middle of the day and spike in the evening, while a battery on a standard self-consumption setting will largely follow the same routine regardless.
Chris, in Paddington, Sydney, saw this with his previous retailer, AGL. He had solar and a battery, but was on a flat-rate plan with a low feed-in tariff. As he put it, he couldn't really take advantage of what was happening in the energy market.
The problem wasn't his battery. It was the way the battery and electricity plan were working together.
With Amber, there is no retailer margin added to the energy price. Customers pay and receive the real-time wholesale price, with Amber's revenue coming from its flat monthly subscription. Smart battery automation can then respond to those prices, charging when electricity is cheap and discharging when prices are high.
Chris now uses his SolarEdge battery this way. Most of the time, SmartShift manages it automatically, although he can take control himself when he wants to. He also uses the app to keep an eye on market prices and feed-in forecasts.
What that can look like on the bill
Chris's quarterly electricity bills used to be around $1,000 in winter with his previous retailer. Since switching, he says they're closer to $100. In summer, some months have been as low as $10, and on some occasions he's been paid rather than receiving a bill.
He estimates his battery will pay for itself in around eight years without a rebate. Under his previous five-cent feed-in tariff, he estimated it would have taken closer to 15 years.
Anthony, in Sydney's inner west, had a similar experience. He has a 9kW solar system and two SolarEdge batteries with a combined capacity of 19kWh.
Before switching, he was exporting 70-80kWh a day in summer for five cents per kilowatt hour, while paying around 35 cents per kilowatt hour for electricity at night. Since switching, he says he earns between $1,200 and $1,600 a year from his system, typically around $100-$200 a month.
During one price spike, he made $375 in a single day by discharging his battery to the grid. He estimates his household is around $10,000 better off after two and a half years, and expects the system to pay for itself three years earlier than originally planned.
A battery is only part of the equation
A Home Energy Rating can tell you a lot about the energy performance of your home, including the contribution of solar and battery storage. If you live in an older home, getting a rating can help identify which improvements could make the biggest difference. You can find an accredited assessor through the Home Energy Rating website.
But a battery's performance doesn't stop at the hardware.
If it's only being used for self-consumption, it's following a fairly simple routine: charge from your solar during the day, use that energy at night. Put the same battery on a plan that responds to real-time electricity prices, and it can do much more - charging when energy is cheap and sending energy back to the grid when prices are high.
So when you're looking at how efficiently your home uses energy, it's worth looking at both sides: the equipment you've installed and what you're doing with it.
If you already have a battery, get a quote with Amber to see what it could do with access to real-time wholesale prices.
