Solar system size: Calculate yours
Find your optimal system size
- Your budget
- Available roof space
- Electricity use
- Future energy plans
Bigger is now better: Think 5kW+It is now better to buy bigger due to the lower cost of solar panels, higher feed-in tariffs and the fast payback on additional kilowatts. If you can afford the upfront cost and have the roof space, we recommend selecting a system size of no less than 5kW; indeed, the new sweet spot of a 6,6kW system with a 5kW inverter is a good option. The price of a 5kW system varies according to your location but expect to pay between $5,500 – $8,000 for a good, reliable unit and a quality installation.
Is the system cost or roof space an issue?If you are not able to stomach the higher upfront cost, or you do not have the roof space, then you should size a system according to your electricity usage, in particular during daylight hours. Let’s delve into the calculations.
Your system size results
How many solar panels do I need?
Buy with confidence
Physical size of solar panels
Why we recommend a larger system
- Higher feed-in tariffs
- Lower cost of larger systems
- Faster payback: cost vs value of additional kWs
- Future planning for storage or greater use
Higher feed-in tariffsHigher feed-in tariffs have made the solar payback and savings equation more appealing. Where once it was desirable to select a system size that met your daily needs, now you can select a larger system and be better rewarded financially for the excess power that you export back to the grid.
Economies of scale of buying biggerThe key cost difference between a smaller system and a larger one is in the labour time it takes to install the unit. It does not take a solar installation team much longer to install a 5kW system than it does a 3kW system. You will need a larger inverter and more panels, but the additional cost of these added components is relatively cheaper.
Cost vs value of additional kWsIf we look at the cost of different sized solar panels, it’s clear that the larger the system, the cheaper the price per kilowatt (kW). We can explain this by comparing solar panel prices in Sydney for 3kW and 5kW solar systems:
- 3kW system in Sydney $4,397
- 5kW system in Sydney $5,866
- 3kw system = $1,465
- Additional 2kw = $734
Fast payback on additional kWsThe cost of increasing the size of the system to 5kW is only $734 per kW. If we assume that you receive a feed-in tariff of 11.1c for every kWh you export back to the grid, it will only take 4.5 years to pay back the extra 2kW; this is assuming that all of the additional solar power output is exported back to the grid. If you self-consume the power, it will pay back much faster. You can expect the panels to continue generating solar power for another 20 years.
System size if you cannot afford a larger unit
System size based on daylight electricity useThe average Australian household consumes 18kWh of electricity each day. If we use a house in Adelaide as an example, you would need a 5kW solar system to generate this amount of power. However, if the household only consumes 40% of its electricity during daylight hours, there is no point in installing such a large system. In this instance, a system that generates on average 7.2kW (40% x 18 kW) of electricity per day would be sufficient. Therefore, a 3kW system is likely to deliver the most affordable solution.
Consider lower winter output
- Daily electricity = 18kWh (Australian average)
- Daylight use = 7.2kWh (Assume 40%)
- Average daily output = 18kWh
- Winter daily output = 8.1kWh
Considering adding a battery?
- Daily electricity = 25kWh
- Daylight use = 10kWh
- Winter electricity 20kWh
- Average daily output = 27.7kWh
- Winter daily output = 18.9kWh
- Do you plan to buy an electric vehicle?
- Do you plan to switch to electric heating and cooling?
- Are you planning to add a pool pump?