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Off Grid Solar Sizing
Off-GridSolar System SizingCalculator
Going off-grid? Use our off-grid solar calculator to estimate the right solar system for your home or business
Calculate your off-grid energy needs instantly
A reliable off-grid system also has to be scaled for winter solar production, battery autonomy and the peak loads your inverter needs to handle. When there is no grid behind you, averages are not enough. For a 4-person off-grid home in regional Victoria, a useful starting point is around 25kWh of energy use per day. But daily energy use is only the beginning.
Why Off-Grid Sizing & System Design Is Different
A grid-connected solar system can be a little too small and nobody notices. When solar production drops, the grid simply supplies the difference. Off-grid doesn't work like that. Your solar, battery and inverter are the power supply. If the system is designed around a sunny-day average, the mistake normally becomes obvious in winter. When the days are shorter, solar production is lower and several grey days can arrive back-to-back.
Battery, Arrary & Inverter sizing for real electricity usage & energy production conditions.
Our calculator gives you an indicative starting point. The final system is designed around your property, your loads and the conditions it has to keep working through when solar production is at its lowest.
Energy Audit
Winter Sizing
Battery Autonomy
Inverter Surge
Generator Backup
Typical 4-person solar power system
Inverter · 2× 10kW
Solar array · 32kW
Battery storage · 30kWh
Daily load · 25kWh/day
A well designed off-grid system considers how much energy the property uses, when it uses it, what winter can realistically produce, how long the batteries need to carry the property and what happens when large loads start at the same time.
Off grid solar calculator
Try the off-grid calculator & Find What Off grid system Suits your home
Use the calculator to get an indicative solar, battery and inverter recommendation based on your household and property. It is designed to get you into the right range quickly. It is not replacement for a professional off-grid system design.
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Answer a few quick questions and we’ll guide you to the right off-grid system based on your setup and energy needs.
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Off Grid Sizing
How We Calculate a Reliable Off-Grid Energy System Setup
When you calculate your off-grid solar needs, There are four numbers we need to get right. They are connected, but they solve different problems.
Energy Needs & Electricity usage
How much electricity will the property actually use?
1
Winter Solar panel Energy Generation
Can the array produce enough when solar conditions are at their worst?
2
Battery Capacity & Autonomy
How long can the property keep running through low-production periods?
3
Inverter & Surge Usage
Can the system actually start and run everything you expect to use?
4
Example Off-Grid Energy Systems by Household
No two properties use electricity exactly the same way, but these examples show how the design changes as the load becomes more demanding.
Weekend Cabin or Small Off-Grid Property
Inverter · 1× 8kW
Solar array · 10kW
Battery storage · 20kWh
Generator Site dependent
The biggest design question here is often not average consumption. It is what happens when the property sits empty for weeks and then everything is switched on over a weekend.
Best suited to a weekender, cabin, tiny home or low-demand property.
Studio · 1 person
Daily load · 10kWh/day
Standard Rural home solar
Inverter · 2× 10kW
Solar array · 32kW
Battery storage · 30kWh
Generator emergency redundancy
A permanent family home with refrigeration, cooking, lighting, pumps, heating/cooling and normal household appliances.The system needs to handle ordinary family life without everyone standing around deciding whether they are allowed to boil the kettle because someone else has turned the oven on.
This is where winter performance starts to matter heavily.
3 Bed · 4 person
Daily load · 25 kWh/day
High-Load High occupancy Rural Property
Inverter · 2× 12kW
Solar array · 42kW
Battery storage · 46kWh
Generator Redundancy strategy
At this scale, the load profile matters more than the number of people living in the house. These systems better serviced by professional advice and than household occupancy rules alone.
Workshops, bore, large homes or multiple heavy loads
5 Bed · 6 person
Daily load · 35kwh per day
Typical High-Load Appliances & Inputs
High-load properties are configured around what needs to run, when it runs, and how much power it draws. Planning needs to account for the additional loads and infrastructure that drive higher energy demand.
workshop machinery
large water pumps
large water pumps
extensive heating or cooling
EV charging
multiple buildings
commercial or agricultural equipment
three-phase loads
Regional Victoria isn't one solar number
Winter Solar Power by Region
Location makes a difference to off-grid sizing, but the difference becomes clear when you look at a location like Ballarat across the year. Systems that looks enormous in summer can be exactly what is required for winter.
Your property still needs its own assessment
Regional data gets us closer to a system design specification. But there is no advantage in pretending postcode data can see a tree standing ten metres from your shed or how the angle or roofing space impacts solar production.
roof orientation
ground-mount options
panel tilt
shading
surrounding trees
local conditions
elevation
available installation area
future array expansion
Winter Solar sunshine hours by Region
The table below uses Bureau of Meteorology mean daily solar exposure data. Solar exposure in MJ/m²/day has been converted to an approximate peak-sun-hour equivalent using 3.6MJ = 1kWh. Ballarat Aerodrome averages around 25.4MJ/m²/day in January, compared with only 6.2MJ/m²/day in June. That is roughly one quarter of the solar exposure.
| Region | BOM Reference Station | June Solar Exposure | July Solar Exposure | June Approx. Equivalent Sun Hours |
| Ballarat | Ballarat Aerodrome | 6.2 | 6.9 | 1.72 |
| Bendigo | Bendigo Airport | 6.9 | 7.6 | 1.92 |
| Geelong | Breakwater (Geelong Racecourse) | 6.6 | 7.4 | 1.83 |
| Grampians | Grampians (Mount William) | 6.1 | 6.8 | 1.69 |
| Castlemaine | Castlemaine Prison | 6.5 | 7.1 | 1.81 |
Source: Bureau of Meteorology long-term mean daily solar exposure. Figures show average solar energy received on a horizontal surface. Equivalent sun hours are calculated from BOM solar exposure using 3.6 MJ = 1 kWh. These are regional climate averages, not 100UP's worst-case system-sizing figures.
Recent off grid solar installations
Recent Off-Grid Energy Projects
Real off-grid installations across Ballarat and regional Victoria. See how different homes, loads and site requirements translate into different system capability and configurations.
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REgional Victoria OFF-GRID Sizing Specialists
Serving Ballarat & Regional Victoria
Need an off grid solar system outside our direct installation area? Talk to us. Depending on the location and project, we may be able to assist with system design, kit supply or an installation partner.
Ballarat
Bendigo
Geelong
Grampians
Castlemaine
Regional Victoria
OFF-GRID SOLAR REVIEWS
More Than a Decade Planning & Installing Solar Systems for Off-Grid Properties
Off-grid has been our sole focus since 2015. That experience matters when you're installing a system where the property is not grid connected.
Fred installed our solar. Very honest very reliable. He goes above and beyond. Tries his best to help. Does a great job. I recommend.
Dino Papa
Verify reviewQuotation & installation process. They have been unfailingly helpful and never failed to communicate pro-actively & effectively.
Andrew Webb
Verify reviewFred did a great job was extremely patient with the slow build Clean and tidy Explained what he was doing along the process
Darcy Joynson
Verify reviewFred installed our system 2 years ago and it has been fantastic. Fred was great and efficient, great communication. Highly recommended
Hayley Richards
Verify reviewUpdated our off grid solar. Cannot recommend this company enough. Fred is very Knowledgeable, honest and very reliable. Great Job.
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Questions FROM Off-Grid Home Owners
Off-Grid Solar Calculator FAQs
What you need to know when considering an off grid system for properties in Victoria. The system should be sized and designed around your property, your loads and the conditions it has to keep working. Including winter when solar production is at its lowest.
Start with your daily energy use, then size the solar array for winter production, the battery for the required autonomy and the inverter for the maximum loads that may operate together.
For quick planning, 100UP uses a starting baseline of around 5kWh/day for the house plus 5kWh/day per occupant.
Your final system may be larger or smaller depending on the property.
For quick planning, 100UP uses a starting baseline of around 5kWh/day for the house plus 5kWh/day per occupant.
Your final system may be larger or smaller depending on the property.
A useful first-pass calculation is: Solar array kW = Daily energy use ÷ (winter peak-sun-hours × system efficiency factor)
For an off-grid system, don't stop at an annual solar average. The design also needs to account for the lowest-production period, local site conditions and an appropriate design margin.
For an off-grid system, don't stop at an annual solar average. The design also needs to account for the lowest-production period, local site conditions and an appropriate design margin.
Battery sizing starts with how much energy you use each day and how many days the battery needs to support the property.
Battery capacity = Daily energy use × autonomy days ÷ usable battery capacity
The manufacturer's actual usable capacity and depth-of-discharge limits need to be used for the final calculation.
Battery capacity = Daily energy use × autonomy days ÷ usable battery capacity
The manufacturer's actual usable capacity and depth-of-discharge limits need to be used for the final calculation.
Calculate the amount of usable energy required first. If you consume 20kWh/day, two days requires 40kWh of usable battery energy before allowing for the battery's usable depth of discharge and other system losses.
The number of physical battery modules then depends on the usable kWh available from each module. That's why we size batteries in kWh, not simply by counting them.
The number of physical battery modules then depends on the usable kWh available from each module. That's why we size batteries in kWh, not simply by counting them.
Bedroom count is a rough indicator, not an electrical load calculation. A four-bedroom house occupied by two people can use less power than a two-bedroom property with a large bore pump, workshop, electric heating and an EV.
Occupancy, appliances, peak demand and location give us a much better answer.
Occupancy, appliances, peak demand and location give us a much better answer.
There isn't a reliable answer based on panel count alone. We need the pump's voltage, running power, starting current, operating hours and whether it starts directly or uses a soft starter or variable-frequency drive. A bore pump's starting demand can be much more important to inverter sizing than its daily energy consumption.
Not necessarily. 100UP systems for permanent homes are designed to reduce normal generator dependency by giving the property enough solar, storage and inverter capacity for the conditions it will face.
Some properties still benefit from a generator as another layer of emergency redundancy. Whether you need one is a design decision, not a rule.
Some properties still benefit from a generator as another layer of emergency redundancy. Whether you need one is a design decision, not a rule.
Because winter combines shorter days, lower sun angles and, in many parts of regional Victoria, extended periods of cloud. Ballarat's long-term Bureau of Meteorology figures show average June solar exposure at only around a quarter of the January figure. A grid-connected home can import the shortfall. An off-grid home has to provide it itself.
No. The calculator gives you a fast starting point. Before we recommend an installed system, we assess the actual loads, property, winter conditions, battery requirements, peak demand and future plans. That's the difference between matching someone with a general system size and engineering the power supply for their property.
10+ years focused on off-grid solar
Ready to Size Your Off-Grid System Right?
If the result looks right, or your property is more complicated than a calculator can handle, tell us what you're planning and we'll work through it with you. Talk to Fred on 1300 489 152 or send a text to 0400 092 621
100% off-grid.
Designed for winter. Built for the way you actually use power.
Ballarat & Regional Victoria