There are a surprising number of factors you can consider when deciding on what size solar system to get. It is worth looking at all of these factors if you are on a budget and have the time, but the very short answer to this question is that the majority of households are getting as much solar as they can fit on their roof.
Solar panels are relatively cheap now compared to the installation cost of solar. The other factor is that battery storage is becoming cheaper, so you don’t just have to think about solar covering your daytime usage. If you decide to install solar, it is often worth covering your roof in panels. But you can see the tradeoff yourself using Photonik.
How much solar can you install?
Every electrical distributor (the company that manages the poles and wires) has different rules about this. You will need to find out what the limit is in your area, if there is one.
What is your consumption amount and consumption profile?
See this article for details.
How can you utilise more of your own solar?
The short answer is, use more power during the day. Do your washing during the day. If you have electric hot water, have showers during daylight hours. If you have gas hot water, you might want to consider changing to electric (and then shower during the day). Use your dishwasher when the sun is out, and your clothes dryer… actually if the sun is out hang your clothes in the sun!
Do you plan to get batteries? Future proof your system.
This is a moot point if you are maximising the size of your solar system already. However if you are debating as to whether you need a larger system or not, based on your daytime consumption, do consider whether you might want to add batteries in future. The cost of battery storage is still currently a little high to make it a no brainer, however it is very likely that the cost will continue to come down over the next decade or so. Remember that a good quality solar system should last you 30 years plus.
If in five years time you might decide to get battery storage, then you should consider sizing your solar system accordingly now. It is not simple to add a few panels to your installed system down the track, for many reasons I won’t go into here.
Consider the example I gave above regarding daytime consumption. If there is a chance in future that you will get batteries, then you would want to consider your full daily usage of 20kW, rather than just your daytime usage of 10kW.
Photonik will help you calculate the size of system you need to cover your usage.
Oversizing your inverter, and back to the simple answer
As mentioned in the first section of this chapter, most companies will quote for a system with a larger amount of panels, than the inverter size. There are three reasons to ‘oversize’ your inverter.
- A 5kW inverter will always output 5kW of AC power if it receives enough input, whereas your 6.5kW solar panel array’s output will fluctuate drastically throughout the day and year. More often than not, your solar array will operate well below its maximum nominal power. Solar panels are also pretty cheap these days compared to the rest of the cost of the system. Your inverter will operate more efficiently if it receives a higher voltage, therefore it makes sense to oversize it and get close to your 5kW output on a regular basis.
- As mentioned in the “How much solar can you install?” section, most electricity distributors will limit your inverter size to 5kW. In order to maximise on that restriction, as mentioned in point 1, you can oversize in order to get closer to that 5kW output.
- Lastly, why not oversize by even more? In Australia, the government rebates are based on the size of the panel array (not the inverter), so in order to restrict consumers from cashing in on rebates for panels whilst having a completely undersized inverter, they have restricted the oversizing to 30% more than the inverter. For good reason, as that is about the max that you would benefit from oversizing your inverter before you would just be wasting the additional solar panels.
After wading through all the details you can see most answers lead us back to getting as big a system that fits on your roof.
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