Battery Storage Explained
How home batteries actually work, what the specs really mean, and how to read a quote without getting bluffed.
Battery quotes are full of numbers — kWh, kW, DoD, round-trip efficiency, cycle life, warranty throughput. Most of them matter. A few of them are marketing. This guide cuts through it so you can compare a Sigenergy SigenStor, a Power Plus LiFe Premium and a GoodWe ESA on the same terms.
kWh vs kW — capacity vs power
kWh (kilowatt-hours) is the size of the fuel tank — how much energy the battery stores. kW (kilowatts) is how fast you can pour fuel out — the continuous power output. A 10 kWh / 5 kW battery holds 10 units of energy and can discharge at 5 units per hour. If your house pulls 8 kW when the air-con and oven are running, that battery will be supplemented by the grid even though it's not empty.
Stackable systems (Sigenergy SigenStor, Power Plus LiFe Premium, GoodWe ESA) let you add capacity and inverter modules over time. That matters because most households underestimate how much battery they actually want once they have one.
Lithium chemistry — LFP is the standard now
Almost every reputable residential battery sold in Australia now uses Lithium Iron Phosphate (LFP / LiFePO4) cells. LFP is more thermally stable than older NMC chemistry, has a longer cycle life, and is the chemistry used by Sigenergy, Power Plus, GoodWe, BYD, Sungrow and Tesla Powerwall 3. If you see a quote for an NMC battery installed inside the house, ask why.
DoD, round-trip efficiency and cycle life
Depth of Discharge (DoD) — how much of the nameplate capacity you can actually use. LFP batteries are typically rated at 95-100% usable. Round-trip efficiency — how much of the energy you put in comes back out. Good LFP systems hit 90-96%. Cycle life — how many full charge/discharge cycles before the battery degrades to 60-70% of original capacity. 6,000-10,000 cycles is the current benchmark, which translates to 15-25 years of one-cycle-per-day use.
Warranty throughput (in MWh) is the most honest metric — it tells you how much energy the manufacturer will guarantee through the battery before pro-rata kicks in.
Hybrid vs AC-coupled
A hybrid inverter (Sigenergy SigenStor, GoodWe ET, Sungrow SH) handles both solar and battery on one DC bus — higher round-trip efficiency, single warranty, cleaner install. AC-coupled retrofits add a battery to an existing solar system via a separate battery inverter (Tesla Powerwall 3, Enphase). Round-trip efficiency is slightly lower but you don't have to replace your existing inverter.
If you're installing solar and battery together, hybrid is almost always the right call.
Backup — read the fine print
Not every battery does whole-home backup. Some only back up a small 'essential loads' circuit. Some need a separate backup gateway box. Some can run off-grid indefinitely with solar topping up; others shut down after a fixed time. Sigenergy, Power Plus and Tesla Powerwall 3 all do strong whole-home backup with the right install; cheaper hybrid systems often don't.
Key takeaways
- kWh = capacity, kW = power. You need both right.
- LFP chemistry is the modern standard — don't accept anything else.
- Warranty throughput (MWh) is the most honest comparison metric.
- Whole-home backup is an install + product decision, not a freebie.
Sources & further reading
- Sigenergy — SigenStor product page
- Power Plus Energy — LiFe Premium
- GoodWe Australia — ESA
- Clean Energy Council — Battery Assurance Program
This article is general information only. Figures change with policy, tariffs and product pricing — for a current quote tailored to your home, start an assessment or contact our team.