Battery quotes use different capacity figures, power ratings and inclusions, which makes headline prices hard to compare. Learn how to convert every quote to usable kWh, continuous kW and price per usable kWh after the discount. To compare battery quotes fairly, convert every quote into the same three numbers: usable capacity in kWh, continuous power in kW, and price per usable kWh after the federal discount. Then check what each quote includes and how its warranty is structured. Two batteries both described as "10 kWh" can differ in usable energy, power and included work by enough to change which one is better value.
Nominal vs usable capacity
Nominal capacity is the total energy the cells can hold. Usable capacity is what the battery lets you draw after keeping a buffer to protect the cells. For LFP batteries the usable figure is often close to the nominal one, but not always, and some sales material leads with whichever number is larger.
Find the usable capacity on the datasheet, usually listed as usable energy, and if a quote does not state it, ask. Also check the minimum state of charge the system will be set to. If the installer configures a backup reserve, that energy sits unused from day to day, which reduces the capacity available to cut your bills even though the battery's rating has not changed.
Round-trip efficiency is worth a glance too. Some energy is lost each time a battery charges and discharges, and a complete system commonly returns around 90% of what went in, so a battery that stores 10 kWh sends a little less back to your home. If two quotes list different efficiency figures, a gap of a few percentage points adds up over thousands of cycles.
Continuous and peak power
Power ratings tell you how much the battery can deliver at once. Continuous power is what it can supply for long periods. Peak power is a short burst, typically lasting seconds, that helps start motors such as air-conditioner compressors and pumps.
Two points often get missed on quotes:
- The inverter can cap the battery. A battery rated for high output but connected to a smaller hybrid inverter can only discharge up to the inverter's limit. Compare the continuous rating of the whole system, not just the battery module.
- Backup power may be lower. Some systems deliver less power to backup circuits during a blackout than they do when the grid is connected. Ask for both figures.
If your evening peak regularly combines cooking, hot water and air-conditioning, a battery with modest continuous power will leave you importing from the grid even while it still holds charge. The inverter guide explains how inverter ratings interact with storage.
What is included, and what is not
Battery installations vary more than solar installations, so inclusions can move the price a long way. Mark each item as included, excluded or not mentioned:
- Hybrid inverter replacement, or an AC-coupled battery inverter
- Backup circuits or a backup sub-board, and which circuits are covered
- Switchboard upgrade, if the existing board has no room
- Energy meter or current sensors for consumption monitoring
- Communication gateway and monitoring set-up
- Wall mounting and protective barriers where needed
- Network application and export settings
- Integration with your existing solar system
A lower price that leaves out backup or switchboard work you actually need is not cheaper in the end. Existing solar owners should also check whether the quote keeps the current inverter and how it will work alongside the battery; the hybrid vs string inverter guide covers both approaches.
Warranty terms side by side
LFP batteries are commonly warranted for 10 years, so the period alone rarely separates quotes. Put three lines next to each other instead: the warranty period, the energy throughput limit (the total energy the battery can deliver under warranty, usually stated in MWh) and the retained capacity stated for the end of the warranty. A battery that reaches its throughput limit early, because it is cycled hard or used heavily in a VPP, can fall out of warranty before the years run out. Compare those figures against the way you expect to use the battery.
A useful extra step is to divide the price by the warranted throughput. For illustration, $9,500 spread over a 30 MWh throughput allowance is about 32 cents for each kWh delivered under warranty, while the same price over 40 MWh is about 24 cents. The battery with the more generous allowance offers more warranted use for the same money, even when the headline period is identical.
Price per usable kWh after the discount
Once the scope of each quote is comparable, work out what each usable kWh costs you:
- Take the final price after the federal battery discount, including any extras you need.
- Divide it by the usable capacity in kWh.
- Check that the quote shows the discount amount separately, so you can confirm it matches the battery's eligible capacity.
Published indicative prices put a 10 kWh battery in Sydney at $8,000-$11,000 after the federal discount, which is roughly $800-$1,100 per usable kWh if the full 10 kWh is usable. Using an example price of $9,500 from within that range, the table shows how the usable figure changes the result.
| Price after discount | Usable capacity | Price per usable kWh |
|---|---|---|
| $9,500 | 10 kWh | $950 |
| $9,500 | 9.5 kWh | $1,000 |
| $9,500 | 9 kWh | about $1,056 |
The federal discount steps down every 1 January and 1 July to 2030, so two quotes prepared months apart can carry different discount values. Confirm current figures on the Clean Energy Regulator's official program page before you sign, and remember that all prices are indicative and confirmed after a site assessment.
Next steps
Build a simple table with usable kWh, continuous kW, backup power, inclusions, warranty terms and price per usable kWh for each quote, and ask installers to fill any gaps in writing. If you want your own usage analysed before comparing sizes, the Battery Feasibility Study in the market starts from $199 (indicative) and covers battery size, backup needs, the federal discount, VPP options and payback. For a battery quote with every line spelled out, request a free assessment from Blue Energy Solar.
Frequently asked questions
Why do two quotes for the same battery have different prices?
The battery module is only part of the cost. Differences usually come from the inverter arrangement, backup wiring, switchboard work, cable runs, wall protection and how much design time went into the quote. Prices can also move as the federal discount steps down. Ask both installers to itemise their scope so you can see whether the gap lies in the equipment or the work.
What do DC-coupled and AC-coupled mean on a battery quote?
They describe how the battery connects to your solar. A DC-coupled battery shares a hybrid inverter with the panels, so solar energy can charge it with one less conversion step. An AC-coupled battery has its own inverter and connects on the household AC side, which makes it simple to add to an existing system. Both work well, and the right choice depends on your current inverter.
Can I compare a quote with backup against one without?
Only after adjusting for it. Backup adds equipment and wiring, so a quote without it will naturally be cheaper. Decide first whether blackout protection matters to you. If it does, ask the lower-priced installer to requote with comparable backup. If it does not, ask the other installer for a version without backup, so you are comparing the same scope.
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