What measurement battery do I would like?: A fast information


What measurement solar panel array do you want to your home? And for those who’re contemplating battery storage, what measurement battery financial institution can be most acceptable? This article consists of tables that present an at-a-glance information, in addition to hyperlinks to extra complete calculators.

Solar system sizing desk (no batteries)

If you’re contemplating solar panels to your home, you’ll get essentially the most worth from them by immediately ‘self-consuming‘ the energy that they produce throughout the daytime. The easy purpose for that is that utilizing the solar your self permits you to keep away from buying costly energy from the grid as a substitute of incomes solely a small credit score for sending it into the grid. This is an important reality about going solar in Australia in the present day.

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Your fee of self-consumption will rely the quantity of energy that you simply use each day, the sample of your consumption all through the day, and the dimensions of the system that you simply set up. You can improve your solar self-consumption ratio by working extra of your units throughout daytime – probably manually, on timers or utilizing a home energy administration system.

The desk under accommodates very tough solar self-consumption ratio estimates for a variety of common solar system sizes and energy consumption ranges. Generally we suggest maintaining to a system measurement meaning your self-consumption ratio stays above 30%.

 Your every day energy consumption Self-Consumption Ratio for Different Solar System Sizes
2kW Solar 3kW Solar 5kW Solar 7kW Solar 10kW Solar
5-10kWh 30% 25% 17% 13% 9%
11-15kWh 48% 38% 26% 20% 15%
16-20kWh 57% 46% 34% 26% 20%
21-25kWh 66% 53% 40% 32% 24%
26-30kWh 73% 59% 44% 37% 28%
31-40kWh 82% 67% 50% 42% 34%

Remember: The desk above is a extremely generalised, indicative information; it doesn’t consider your location or the lean & orientation of your roof – to not contemplate system costs or monetary particulars like payback interval. If you’d wish to take a extra detailed look, use our Solar PV System Payback Estimator or our Simple Solar System Sizing Estimator.


The under video offers a run by means of on find out how to choose the precise solar system measurement


Tesla Powerwall and SolarEdge comms box 1Picking the Correct Solar and Battery System Size

Using Sunwiz’s PVSell software program, we’ve put collectively the under desk to assist customers select the precise system measurement for his or her wants. PVSell makes use of one year of climate information Please learn the paragraphs under and do not forget that the desk is a information and a place to begin solely – we encourage you to do extra analysis (and get extra opinions) earlier than deciding on a system measurement.

About solar & battery system sizing ▼

Battery storage system sizing is considerably extra sophisticated than sizing a solar-only system. While solar panels generate energy, batteries solely retailer it, so their usability (in addition to their worth) is predicated at first on the energy accessible to fill them up (which often comes out of your solar panels). The measurement of the solar system put in (or to be put in) will often be the first dictator of the dimensions vary of the batteries which could be paired with it, adopted by the home’s energy consumption ranges and utilization patterns; if a home makes use of quite a lot of energy throughout the day, there might be much less solar accessible to enter the batteries.

In reality, an important factor to have a look at is the connection between the quantity of energy that the family consumes each day and the quantity of energy that the solar panel system produces day-to-day.

About solar batteries & energy targets ▼

Further compounding the matter is the truth that folks have completely different targets in the case of home solar batteries: The major aim for most individuals is to save cash, however energy independence and backup power are additionally held in pretty excessive regard. Battery storage system sizing is subsequently a really explicit and extremely individualised matter. If a battery is just too giant, will probably be underutilised, and whether it is too small it could not obtain the energy independence targets of the family the place it’s put in.

To account for this within the desk, the place the solar system measurement is giant sufficient we’ve included two figures: The first being the utmost really helpful battery measurement for monetary functions (attempting to optimise for payback interval and return on funding), and the second being the really helpful most for energy independence (the variety of days the home can go with out drawing from the grid). Please word that techniques whose goal is energy independence might be considerably costlier and often have a lot poorer payback occasions than people who don’t due to the necessity for redundant, extra capability which can sit idle and unused more often than not.

Just a few caveats… ▼

Bearing all this in thoughts, the desk under goals to offer some ballpark figures, which ought to not less than work as a place to begin for solar & system measurement choice. The limitations of the under desk embody:

  • Figures are based mostly on a state of affairs the place the solar panels are north-facing and pitched at a 30 diploma tilt angle – different tilt angles and orientations will bear completely different (and sometimes much less beneficial) outcomes
  • The figures needs to be acceptable for many of Australia, however could also be a bit optimistic for Victorian and Tasmanian houses, the place bigger solar techniques could also be mandatory
  • The mannequin state of affairs additionally assumes that the family makes use of a major quantity of energy throughout daytime (‘high days, evening peak’ utilization sample) – a home that makes use of much less energy throughout the day might doubtlessly profit from a bigger battery financial institution measurement (relying firstly on the dimensions of the solar system)
  • The battery system sizes are given in kilowatt-hours (kWh); in our modelling, this quantity refers back to the full, usable capability of the battery in query, after ‘depth of discharge‘ is factored out

The battery financial institution sizing calculator

The battery financial institution sizing desk

Your every day energy consumption

Largest really helpful battery measurement for…

Solar system measurement
2kW 3kW 5kW 7kW 10kW


Maximising returns: 5kWh 4kWh 4kWh 4kWh 4kWh
Maximising energy independence: 22kWh (3 days of energy autonomy) 35kWh (5 days of energy autonomy) 35kWh (5 days of energy autonomy) 35kWh (5 days of energy autonomy)


Maximising returns: 4kWh 7kWh 9kWh 8kWh 8kWh
Maximising energy independence: 40kWh (3 days of energy autonomy) 65kWh (5 days of energy autonomy) 65kWh (5 days of energy autonomy)


Maximising returns: 3kWh 6kWh 13kWh 12kWh 11kWh
Maximising energy independence: 55kWh (3 days of energy autonomy) 90kWh (5 days of energy autonomy)


Maximising returns: 2kWh 5kWh 12kWh 16kWh 15kWh
Maximising energy independence: 23kWh (0.77 days of blackout safety) 70kWh (3 days of energy autonomy)


Maximising returns: 1kWh 4kWh 11kWh 18kWh 18kWh
Maximising energy independence: 40kWh (1.5 days of blackout safety)


Maximising returns: 3kWh 10kWh 17kWh 23kWh
Maximising energy independence: 27kWh (0.7 days of blackout safety)

Glossary for this desk ▼

  • ‘Maximising returns’ – refers back to the battery largest battery financial institution measurement (in kilowatt-hours, kWh) that may be put in which the solar system can cost as much as full capability not less than 60% of the times of the yr. The figures on this desk are for the most important really helpful measurement; smaller battery banks will often provide higher returns.
  • ‘# days of energy autonomy’ denotes the utmost estimated variety of consecutive days {that a} home can go with out drawing energy from the grid within the occasion of a number of days of unhealthy climate; you need to use this as an approximation of how ‘off-grid ready’ your system might be (so long as your energy consumption ranges don’t improve). Best observe is to have not less than 3-5 days of energy autonomy constructed into your system for those who plan on going off-grid (which is an possibility it is best to pursue solely after cautious consideration).
  • ‘# days blackout protection’ refers the the period of time that you simply’d be capable to proceed consuming energy as per normal within the occasion of a grid outage (you might be able to lengthen this by rationing your energy utilization). Having blackout safety requires some extra battery capability, in addition to gear that allows backup power performance (learn extra right here). We’ve solely included a determine for battery backup in cases the place the battery could be charged to full capability not less than 60% of the times of the yr.


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Since 2008 our data and complicated software program has allowed over 180,000 Australian households and companies to make a well-informed alternative on their solar & battery installer.


James Martin II

James Martin II

Contributor at Solar Choice

James was Solar Choice’s major author & researcher between 2010 and 2018.

He is now the communications supervisor for energy expertise startup SwitchDin, however stays an occasional contributor to the Solar Choice weblog.

James lives in Newcastle in a home with a bizarre solar system.

James Martin II

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