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3. Sizing a system
Start with your average daily usage
Your daily usage is the total amount of kilowatts you have drawn from the grid. Often on your energy bill it will have the daily average of kilowatts summarised on the first or last page of your bill.
Let's say that the average daily usage is 15 kW. Some of that usage would be in the evenings and some during the day.
You would want a solar system that produced over 15 kW daily and a battery big enough to cover your evening use.
It is usually recommended to size the solar and battery system larger so that in poor weather or times where your usage increases you can still meet your needs.
What a 6.6 kW system looks like
A 6.6 kW solar array typically consists of 14 panels. The panels being 475 watts each and so 14 x 475 = 6650 watts, or 6.6 kW.
Daily production of this system is based off 5 hours of sun and outputting roughly 5 kW an hour.
This would produce on average 20-25 kW a day. On a hot sunny day in summer it can do more and on a cloudy winter day it will do less.
Sometimes people will need to consider if they have shading issues too that might influence the solar production.
- • 14 panels x 475 watts = 6.65 kW
- • Often around 5 useful hours of production per day
- • A common residential entry point
What a 13.3 kW system looks like
A 13.3 kW solar array would be double the panels and double the production.
Producing 40-50 kW on average, this solar array is typically 28 panels.
For most residential properties this is a huge system and can often cover most of the roof depending on the size of the house and available roof space.
Battery sizing follows your night demand
For most people with a 15 kW daily usage, a 10 kW battery size may be enough.
If you are prone to grid outages, poor weather runs or expect your usage to increase, then you may want to size your battery up a little.
To connect to a local installer for a tailored assessment and design, use the assessment link below.
Rough system guide
Play with your usage or bill and get a rough system option.
This is a planning tool only. Final design still depends on roof space, shading, switchboard condition, battery goals, and installer scope.
Suggested solar
6.6-10 kW
Common panel count
around 14-21 panels
Typical solar output
roughly 20-38 kWh a day
Battery range
around 10 kWh
Based on roughly 15.0 kWh of daily usage, this guide points toward 6.6-10 kW of solar and around 10 kWh of storage as a starting conversation.
This is the range many households fall into. It leaves room for daytime coverage and a practical amount of evening battery support.
Want the real answer for your roof, usage, and battery goals? Move from a rough guide to a tailored assessment.
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What is the most useful number to start system sizing with?
Your average daily usage from the bill, because it tells you how much energy the solar and battery system needs to cover across the day and evening.
For many homes around 15 kW a day, what is a common battery starting point?
Around 10 kW of battery capacity is often enough, then you size up if outages, poor weather runs, or future growth matter more.