Solar is an excellent way to get away from the grid, shrink your monthly power bills and go green. But, we know that getting the perfect system is not as easy as going to a store and walking out with a solar panel or two.
To help you navigate buying your first solar panels, battery and inverter, we’ve put together a quick guide to all the things to know and look for while researching.
Buying rooftop solar panels
To buy the right rooftop solar panels for your property’s needs, you’ll be looking at the size of the panels themselves, the suitability of your roof and any available government rebates. You’ll also need to check how much power you use each day, and learn a little bit more about your local climate.
Factors to keep in mind when comparing solar panels include:
1. Suitability of your roof and property
Typically, solar panels go on your roof. As such, it’s important to assess the condition and quality of your roof before making any purchases. Additionally, consider your local climate conditions to check that they’re appropriate for generating solar power.
Your roof: Must be structurally sound and capable of handling the added weight of the solar panels, even in windy conditions. It should also face the right direction so the panels can catch the maximum amount of sunlight.
Your climate: Must be appropriate for generating solar power, with good sunlight hours and lower risk of extreme wind (though, solar panels are more tolerant of wind and cloud than you might think).
- Pro tip: You may need expert help here, as assessing the suitability of a property for solar power can be quite complicated. Learn more about going solar here, or contact our team about getting your property assessed.
2. Daily energy use
How much power does your household or business use each day? This will help you figure out what size of solar system you require.
Check your power bills and find the chart that tells you how much electricity you’ve used, in kilowatt hours (kWh), each day. Calculate your average annual consumption so you can see how it changes.
3. Solar system size
Solar panel output is usually measured in kilowatts, not kWh, so we’ll need to convert one number into the other. Don’t worry though, it’s easy: just take your average energy consumption and divide that by four. Then add a couple kW onto this number to get your ideal system size.
Calculation: Daily usage (kWh) / 4 = ideal solar panel system size (kW)
Example: If you estimate your daily usage throughout the year is 32 kWh, dividing it by four produces the number eight. So, you know that a 10 kW system is likely correct. Most people add 25-30% to their system size, so the ideal output can still be reached in cloudy conditions, during winter months or to future-proof the system for higher energy consumption in the future.
- Pro tip: Add a little extra to your daily kWh if you think you’ll be installing new heat pumps or other plant and equipment soon, to future-proof your system.
4. Product specifications: Numbers to know
Efficiency
A solar panel’s efficiency rating is how effective it is at converting sunlight into electricity. Generally, the larger this number the better. Ratings of 18-23% are common.
Temperature coefficient
Solar panels love direct sunlight, but operate less efficiently when it’s really hot. This is the ‘temperature coefficient’ (often called ‘Pmax’). To make it simple, it tells you how well your panels will operate at temperatures above 25 degrees C. It is expressed as a percentage change per degree C.
Example: A Pmax of -0.37%/°C tells us that for every degree over 25, power output will drop by 0.37%. Therefore, any Pmax closer to zero is usually better.
Power tolerance
This tells you how close your power output will be to its advertised rating (in watts). This could be a positive number, a negative number or both.
Solar panels tend to perform differently in a real-world situation than they do in a lab, and manufacturers account for that by letting you know the power tolerance rating.
Example: If a 420-watt panel says it has a power tolerance of +10 watts, it’ll likely deliver 420-430 watts to your property. If the tolerance rating was +/- 10 watts, it could deliver anywhere from 410 to 430 watts. Higher positive numbers are typically better, and negative numbers typically worse.
Feeling a little uncertain? You can skip the need to learn all of this info when you use a professional solar installer – identifying the right-fit system for your property is part of the consultation process.
5. Warranty
Solar panel warranties differ between manufacturers, but typically start at 25 years. Your solar installer should generally offer a workmanship warranty (ours is 10 years).
You’ll also typically find solar panel manufacturers offer two warranties, one for the product and one for the performance of the product. Performance warranties are the ones which typically last 25+ years, guaranteeing your product should deliver a minimum percentage of its claimed power rating after a certain period (such as 80% after 25 years).
The product warranty is what covers repairs and faults, and is usually smaller: 10+ years.
6. Rebates and discounts
Don’t pay full price if you don’t have to. Most Australians have access to a range of government rebates and discounts to help bring those installation costs down.
The federal Small-scale Renewable Energy Scheme is the most common, available across Australia. Then there are state-level schemes too, like VIC’s solar panel rebate or NSW’s battery rebate. All three can get you discounts on the up-front costs of your system.
Before paying for your solar system, always check online to see what’s available near you. Or, talk to your solar installer about applying for rebates on your behalf.
Buying a solar battery
On to your battery next. Like with solar panels, the key thing to watch out for when buying a solar battery is that you get one which is the right size for your daily needs. Too small and it’ll run out quickly; too large and you’ll be paying for battery storage you don’t use.
Digging into some of those specifics:
The big factor: Battery capacity
A solar battery’s capacity is how much charge it can hold, measured in kilowatt hours (kWh). You’ll notice that this is the same unit of measurement found on your electricity bill, so this one’s easier to calculate than solar panel size.
Look for a battery which can store either all or a large proportion of your daily power needs.
Learn more: Solar battery sizing guide: What size battery do you need?
Other factors to look at
While capacity is one of the major deciding factors of choosing a solar battery, there are a few more terms to familiarise yourself with:
- Power output: The amount of electricity a battery can provide at one time (i.e. the number of appliances it can support).
- Depth of discharge: The amount of charge you can use without impacting the battery’s lifespan.
- Round-trip efficiency: The energy efficiency of the battery.
- Cycle life: The number of complete charge and discharge cycles a battery can handle before it significantly degrades.
- VPP capability: Whether or not the battery is compatible with joining a VPP network.
We cover all of these in more detail in our guide: ‘What to look for when buying a solar battery’.
Buying a solar inverter
A solar inverter is the third piece of the solar system puzzle – it takes the energy generated by your solar panels and converts it into energy your property can actually use, which is then stored in the battery.
There’s a few extra things to keep in mind here to ensure you get the right solar inverter for your property, solar panels and battery:
1. Type of inverter
Inverters come in a few forms, which all do the same job a little differently.
- String inverters are the most common for households. Here, all your solar panels are connected to a single inverter.
- Microinverters are smaller inverters attached to each individual solar panel. These are more common when the roof is a complex shape, and they allow you to monitor a solar panel’s individual performance.
- Hybrid inverters are essentially modern string inverters that also allow you to connect a battery to the system.
- Battery inverters are typically used if you’ve already got a solar system and want to retrofit new battery storage – they let you add a battery where there’s already an existing inverter.
2. Compliance with Australian standards
Double check that any inverter brands you’re looking at have been approved by the Clean Energy Council and meet Australia’s standards. You may not be permitted to install an inverter that isn’t approved, or it could make you ineligible for government rebates on the installation cost.
This shouldn’t be a problem with the majority of brands available in Australia, but it’s always worth checking.
3. Inverter size
Like solar panels or a battery, you need the right size of inverter to ensure its suitability for your property.
Inverters are also measured in kilowatts, which tells you how much power they can manage. An inverter’s maximum output capacity should meet at least 75% of your solar system’s capacity.
Example: For a 10 kW solar array, you’d want anywhere from a 7.5 kW to 10 kW inverter.
Get help from the experts
At Think Renewable, we have licensed solar experts across the country ready to help with all of the above. Our electricians can come to your property for free, assess your needs, and recommend the ideal system type and size to meet your unique requirements.
Book a free, no-obligations consultation to learn more about what might work for your property, how much it’ll cost and how to bring the price down with government incentives.
