Buying a home battery: what to know before you get quotes

Wholesale costs are only one part of a power bill, and network costs are still rising in some areas, so your own bill may not fall by as much.

Cheaper grid power also means each kilowatt-hour a battery replaces is worth a little less. Ask installers to base any savings estimate on your current tariff, not last year's, and check whether a time-of-use plan, a virtual power plant or the Solar Sharer Offer's free midday power changes the numbers.

The evening peak is still when the grid works hardest. A home battery covers your own evening use with solar you stored during the day, and that doesn't depend on what the wholesale market does. In AEMO's sample, homes with solar and a battery took about three-quarters less from the grid between 4 pm and 9 pm than homes with solar alone.

Say your data shows you use about 9 kWh between 4pm and 7am, and your solar exports about 15 kWh on a typical day. To deliver 9 kWh after losses, the battery needs roughly 10 kWh of usable capacity, and your exports can fill it on most days. A 20 kWh battery would rarely fill, so the extra capacity would add cost without adding much benefit.

The federal discount also shapes the decision. It pays the full rate for the first 14 kWh of usable capacity, 60% of the rate from 14 to 28 kWh, and 15% from 28 to 50 kWh. Large batteries cost more per kWh after the discount.

Most home batteries are lithium-ion, in two main chemistries. A NSW Government guide notes lithium iron phosphate (LFP) is generally considered safer than nickel manganese cobalt (NMC) because of its better thermal stability, while stressing that overall product quality matters most. The chemistry is on the datasheet, so ask if it isn't in the quote.

Installation must follow the Australian standard AS/NZS 5139. Guidance from Australia's electrical regulators lists places a battery must not go, including ceiling spaces, set into wall cavities, under stairs or along exit and escape routes, on most roofs, and where a vehicle could hit it. There are also minimum distances from windows into living areas and from exits. If the battery is close to a wall of a habitable room, a non-combustible barrier is needed.

Fire and Rescue NSW recommends a cool, ventilated, low-traffic spot away from entries and exits. A garage wall is a common choice, but ask how the installer will protect the battery from cars.

The federal Cheaper Home Batteries Program cuts the upfront cost. The Clean Energy Regulator puts the discount at around 30%, and installers normally apply it directly to the quote. To qualify, the battery must be on the Clean Energy Council's approved list, installed by a Solar Accreditation Australia installer with a battery endorsement, compliant with AS/NZS 5139, and installed with new or existing solar.

The discount steps down every six months until 2030, so the same battery costs a little more over time. Some states add their own support. See battery rebates for the current details in your state.

Eligible batteries must be able to join a virtual power plant (VPP), but you don't have to join one. A VPP lets a company use some of your battery's charge in return for credits or payments. Some state incentives, like the NSW one, require it. Check how much charge is kept for you before you sign up.

Look for a retailer that has signed the New Energy Tech Consumer Code. Signatories commit to clear information, no pressure selling, itemised quotes and written contracts, and to honouring warranties. Check the installer's accreditation and licence numbers, and get at least two or three quotes so you can compare like with like.

When you request quotes through Energy Quotes, up to three participating installers who service your area will contact you. Use the checklists on this page to compare what they offer.