solar faq

FAQ - Solar Savings Breakdown

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Solar Savings Calculations

How do my solar system’s savings work?

It's as simple as, solar system's panels on your roof = generating free power from the sun, all day. This means everything in the home can be powered for free, so you’re not buying any power from the grid while your system is making power instead, and more than half of your bills are gone because you’re not buying any power from the grid most of the day.

That’s only half the story though. A good quality solar system, installed by an expert designer and with enough panels, can make 4 or 5 times more power than you need in the middle of the day.

How do you come up with solar savings and figures?

In short, we don’t. We use a program called Pylon that is more trusted than humans. The maths behind solar savings and calculations is often one that puts even the most analytically minded to sleep because there are so many variables at play when it comes to solar energy. These include how much energy is generated from the sun and forecasting the effects when every property and energy use profile is unique.

There are also hundreds (yes, HUNDREDS) of energy plans available to consumers, each with as many as 7 or 8 separate fees or rates to contend with from peak-usage rates to GST and even Pay-On-Time Discounts. Due to the complexity, we combine a team of consultants (all with 5-10 years of experience designing systems locally) with state-of-the-art software.

What if I don’t use or need all my solar system’s energy?

All the extra leftover power gets sold back automatically into the grid, and you get paid credits. Basically, you’re letting your energy retailer on-sell the power you couldn’t use to your neighbours, and they split the profit with you. In enough quantity, the credits can even offset the rest of the power you use at night.

This means that you will effectively be selling your excess electricity to your energy retailer and will receive a credit on your energy bill for doing so. Generally, this is referred to as the “Feed-in Tariff”.

How long is the payback period for paying off my solar power system?

Go Sunny Solar Adelaide has calculated 5 years as the payback period, or the amount of time it will take for your solar panels to pay themselves off.

This calculation is based on a number of factors, which include the solar system size, the plentiful sunshine available for South Austrlaians, good feed in tariff rates and average electricity rates.

How many panels do I need to wipe out my bills?

In short - a lot. 

Why? Our power usage and power prices are going to continue to increase.

Power Usage - Household electricity consumption continues to be on the rise, as we shift further online, improve the power of appliances and find new gadgets with bigger batteries more and more. 

Power Prices - To make things worse, the rates of electricity prices have significantly skyrocketed over the past decade and are expected to keep rising.

To combat this, going solar can help you set yourself up for the future. You can overwhelm your bills by generating higher volumes of solar power and have enough free power to overwhelm night usage.

Does solar still work in winter?


The latest advancements still produce significant results during all seasons. It is true that Winter days have several hours less sunshine than Summer days. Less hours of sunlight will mean less free power is produced.

Tailoring a solution to meet your needs in all seasons, or getting a larger system, is the best way you can ensure enough production all year round.

We have a comprehensive breakdown HERE.

Why do you recommend a certain system size?

The size of your solar system is restricted by a few factors. SA Power Networks impose restrictions on most homes, limiting the maximum solar output per household meter (NMI), to reduce strain on the grid when everyone is exporting lots of excess energy.

Many homes have limitations in the roof space, structure, material and orientation that confine the available area for compliant solar, to less than what they may ultimately want or need.

This can require a deal of experience and creativity to design around these obstacles to ensure you can get as many solar panels as you need, to free yourself from bills as much as possible.

What is load shifting?

Load shifting, in its simplest form, means to shift energy usage from nighttime to daytime in any way and any amount.

How do I maximise the value of my solar system?

There are a few things you can do to maximise the value of your solar system, including:

- Performing heavy load tasks during the hours your system is generating energy. These heavy load tasks are usually tasks such as using the heater or air conditioner, using the dishwasher and using the washing machine.

- Reduce your overall energy consumption: Simple changes like turning off lights when you leave a room or using a power strip can help reduce your overall energy consumption.

- Monitor your system: Use the WiFi monitoring tool that comes with your Go Sunny system to track the performance of your solar system. This will help you identify any issues and ensure that your system is operating at peak efficiency.

How long does it take to see a benefit with solar?

The benefits of solar are immediate. As soon as your system is installed, you will start saving money on your electricity bills. This money saved can immediately go into paying off your solar system with our ANYTIME Solar Plan!

In addition, you will be doing your part to reduce your carbon footprint and help create a more sustainable future. Solar is a long-term investment that will continue to benefit you for years to come.

Do I need battery storage?

In some circumstances, home battery storage can also help store free power to release at night.

Outside of the worst few weeks of winter, most solar systems in powered homes can produce enough free power to cover all your needs, which quickly translates to thousands of dollars back in your pocket every year, for decades.

Still need help piecing it all together? Jump on a quick call with our assessment team to talk about solar batteries, and we can answer all your questions and cover things in more detail.

Bills and Energy Usage

What is a kilowatt of solar and how do I work that out?

The size of your system is calculated as the “umber of Panels” multiplied by the “strength” or “output” of each panel.

For example, our most popular system size is a 13.2-kilowatt system. It has 33 solar panels and each panel is 400 watts. You could have old 370-watt panels, from a few years ago, but you would need 36 solar panels for the same/similar size and output of 13.2kW.

If you want to dive deeper into it, there’s plenty more out there. You can visit Solar Quotes for more information.

What is a kilowatt and a kilowatt hour?

1000 x watts of energy output = 1 x kilowatt

1 kilowatt of energy output x 1 hour of operation (at 100%) = 1 x kilowatt hour

Just like liters of petrol in your car are made of 1000 milliliters, you can also measure how many kilometers your car can travel on average per liter to measure a cars fuel efficiency. The same is true for energy usage.

What’s the difference between a kilowatt and a kilowatt hour?

In simple terms, a kilowatt refers to the rated output of an appliance, similar to horsepower in a car or grip strength in an arm wrestle. 

“How powerful is this thing compared to another.”

A kilowatt hour, measures the amount of energy accumulated or used over time (hours).

On energy bills, we see the total kilowatt hours consumed by all appliances in total. 

In summary, to calculate kilowatt hours per appliance, you multiply the rated output (eg. 2kw dryer) by the hours of operation in any time period (eg. 2 hours per week). In this example, the dryer used 4 kilowatt hours of energy in a week.

If you want to dive deeper into it, there’s plenty more educational material at your disposal.

How many kilowatt hours will my solar system produce?

A solar system with 13kw of panels, and a 10kw inverter, can produce up to 10kW per hour. This represents its maximum hourly output potential/threshold. A 10-13kw system will often produce 30, 40, 50 kilowatt hours of energy as it often operates far longer than just 1 hour per day. 

Importantly, it should be noted that every hour of sunlight does not have an equal effect on solar production, there are always natural losses. Sunrise to sunset might be 11 hours on a particular day, but only be the equivalent of 4.5 hours at 100% production.

Why does my system have an inverter with a lower output than my solar panels?

There are natural losses and fluctuations from solar panels, due to changing sunlight conditions, it would be rare for a panel to ever hit 100% efficiency even if it were the highest quality under lab conditions. Whereas inverters incur almost no loss of power (<1% typically). 

To compensate for the more significant, natural drops in output - installing up to 33% extra panel output is the best way to maximise output.

If I have 6.6kW panels but only 5kW inverter, will that overload or break my inverter?

Solar inverters PULL electricity from the panels, the panels do not PUSH electricity into the inverter, so there is no risk of a system overproducing energy and overloading the inverter.

This goes the same for systems with 13.3kW panels with a 10kW inverter.

Is it against network regulations or CEC guidelines to have a system with more panel output than inverter output?

The regulations require Solar PV Installations to be within 33.33% of the total inverter output. In other words, a system should not be connected if it is less than 66.66% or more than 133.33% of the inverter output. 

For example - a 5kw inverter can have up to 6.66kw of panels installed and a 10kw or 5kw + 5kw inverter setup would require a minimum of 6.66kw.

Solar System Basics

Is it normal for my inverter to drop out or switch off during the day for a few minutes?

This is very normal unless it is happening continuously or frequently. All good inverters have inbuilt and automatic protection and safety measures that shut down the inverter when the voltage is too high.

The inverter will then wait or detect that the voltage has returned to a stable threshold and power itself back on. This protects the inverter's lifespan and warranty and the electrical infrastructure and occupants of the house.

Why does my system sometimes drop out or turn off for a few minutes?

Why inverters switch off or reduce output is largely because of the grid/network experiencing a voltage spike. This is usually a sign of the grid being overloaded, but can also be helped or hindered by your inverter’s settings. For more information regarding grid voltage spikes and inverter shutdown’s in SA, please see the material from SAPN.

What are the different types of meters?

Most residential meters can be categorised as either:

  • Analogue - Has a magnetic spinning disk and a ticking total counter
  • Digital - Has a small screen and a button that displays a reading
  • Smart / Active Stream - Has programmable functions and features, as well as internet connectivity for sending/syncing/reporting directly to retailers and the network

From there, meters can be classified as typically Single or Three Phase (Occasionally Dual Phase/2P).

Do I need to have or get a smart meter?

SA homes are currently undergoing a statewide upgrade project, SA Smarter Homes initiative, that is implementing restrictions and deadlines for the upgrade. Smart meters have the added functionality of live reporting of energy use remotely to retailers and customers via internet.

Bills, Rates, Tariffs and Charges

What is a supply charge?

This is a fixed amount charged per day for the benefit of having an active connection to the grid, regardless of how much or how little energy you consume. Think of it like the ante in a poker game or registration for your car. Regardless of how often you drive, your car needs to be registered to hit the road.

The average billing cycle is every 91-92 days if quarterly. Most supply charges start around 80 cents per day and can go up to over a dollar quickly. This means you could likely expect this amount to be about $90 per quarter including GST, give or take.

What is the peak rate?

Peak rate is the highest rate per kW charged on a bill. It refers to the energy you consume during the grid’s highest demand time frames. Although they can vary amongst the retailers, the windows are typically 3pm until 1am and 6am until 10am.

These windows align with when moist households are most commonly at home and using a large number of appliances, such as after school or work, through until after midnight, or in the morning when most people are waking up and preparing themselves for the day. This can be as high as 50cents per kilowatt hour once factoring GST on top.

What is the controlled load/ancillary rate?

Some households, primarily those who have electric hot water systems, have a separate/secondary meter designed to operate overnight in low-demand periods at a reduced rate. Typically these rates are 35-45% less than the peak rate (+GST).

What is a Time of Use Tariff (TOU)?

Time of use tariffs are being utilised at an increasing rate as electricity grid infrastructure rolls out smart meters. This allows further customisation of energy charges to automatically self-adjust with grid demand. The carters become flexible and are designed to adjust to mimic the increases or decrease in the cost to supply energy with the live demand.

How does GST (Goods & Services Tax) affect my bills and potential savings with a solar system?

Energy supply is considered a good or service that qualifies for standard federal GST of 10%. This mostly means, after your usage has been totaled and multiplied by your rates of power, GST is then added. 

Example: Your bill says for the quarter you consumed 1000 kw/h of energy, at a rate of $0.418c per unit. Your usage charges are $418 + GST so that part of the bill cost you 

$418 x (100% + 10%) = $418 x 1.1 = $459.80 incl. GST.

Most importantly, this makes your effective (actual) rate for this energy, not $0.418c as stated, but the rate is equivalent to $0.418 x 110% = $0.4598c incl. GST. 

So while it feels like you may have a lower rate, you need to factor in the GST that is or would have been applied afterwards, when calculating usage or savings, past or as a forecast/prediction.

The great news? 

You won't pay GST on free solar power because you aren't receiving it as a good or service. So when you save with solar, you save at $0.4598c per Kilowatt hour. In a way, solar saves you 10% of your usage costs instantly because it isn’t subject to GST anymore. 

Solar Subsidies and Exports

How much is the Australian Government solar rebate?

The Australian government subsidy covers $2,000 - $7,000 off the full cost of all the equipment, installations and charges, as a point-of-sale discount that makes the better systems affordable.

Adelaide households were able to apply for the Home Battery Scheme and save money, but that has now finished.

What is a Feed-in tariff or “Solar Rebate”?

A feed-In tariff is the per kilowatt hour rate in dollars/cents for energy exported (or “fed back”) into the energy grid, that was generated from a solar PV system.

This was once commonly referred to (incorrectly) as a rebate, when the government paid lucrative incentives for early adopters of renewable energy technology (Pre 2013). These are known as premium feed-in tariffs. Feed-in tariffs are still alive and active, they are now negotiated between an energy provider and an energy customer, with a range of different rates and plans available. 

If you would like to see what the maximum feed-in available in your circumstances with each energy provider, find out more here.

What is a Premium Feed-In Tariff?

Premium feed-in tariffs are those granted to legacy solar system owners who had systems installed and approved before 2013, 2011, 2010 and 2008. 

Each time frame secured a subsidised rate for exported electricity (the original solar “rebate”) between 44 cents and 60 cents, depending on the available rate when the system was installed. These progressively diminished initiatives dictated the guaranteed price power kilowatt hour as well as how long the tariff could be held for (until expired).

A complete breakdown for anyone who is interested in determining if their older system or a system at a property they recently acquired can be found here.

Can I keep a premium feed-in tariff if upgrading my system?

If you modify the solar output (size of panels/inverter), beyond the original system output on file with SAPN, removal of your premium feed-in will be triggered. 

This means you CAN replace your old system for a newer more efficient system, but only to the same or lower output.

Can I get a premium feed-in tariff back if I had it before?

You cannot add to or replace your system with a larger, more powerful system AND keep the premium feed-in (I know, nice try, we wish).

Can I take my premium feed-in tariff with me to a new property if I sell my home?

PFITs remain with the system at the point of install and are not transferable to other properties or system owners.

Can I claim/get a feed-in credit or use a premium feed-in tariff on my electricity account if I am renting a house that has a system on it?

In most scenarios, whoever owns and pays the electricity bills with their retailer, is the one who stands to benefit from any solar or tariffs. PFITs remain with the system at the point of installation and are not transferable to other properties or system owners.

Can I use a previous owner's eligible premium feed-in tariff if I now own the property and system, but didn’t purchase the original system?

In most scenarios, whoever owns and pays the electricity bills with their retailer, is the one who stands to benefit from any solar or tariffs. PFITs remain with the system at the point of installation and are not transferable to other properties or system owners.

How much is the Australian Government solar rebate?

The government subsidy covers $2,000 - $7,000 off the full cost of all the equipment, installations and charges, as a point-of-sale discount that makes the better systems affordable. 

Can I claim the federal government’s solar subsidy/rebate again if I have solar already?

Yes, you CAN claim the federal government subsidy on new panels even if it was already claimed for a previous system. So you can still have a larger replacement and take advantage of approx. 25-30% discount, whether it was you OR another individual who installed the older system and claimed that subsidy.

How many times can I claim the solar subsidy?

As many times as you like until it is no longer available.

You cannot of course claim the subsidy twice for the same panels or system, but you can claim for multiple properties, multiple systems on the same property etc. 

The subsidy, is typically paid to the solar installer or retailer, who passes it on as a point of sale discount of the purchase price. This makes one or multiple solar systems attractive and affordable investments for almost any homeowner. 

The subsidy only covers certain homes and criteria, for example, a ground mounted system isn’t classified as residential rooftop solar, and wouldn’t be eligible for STCs (Small-Scale Technology Certificates) under the SRES (Solar Renewable Energy Scheme).

Is it worth holding off on making any upgrades or changes to my solar system if I have a Premium Feed-In Tariff?


Why? The vast majority of systems installed before 2008-2013 were extremely expensive to purchase ($20-50k) and at the time, power needs or usage, was less than half that of today's average modern household.

This means most systems with a premium feed-in are either:

  • Very small with a low output (1-2kw, 8-12 panels)
  • Very old technology with a degrading output (10-20 years, 40-85% original output)
  • Both

With today's energy needs sky high and still rising, any broken, small or outdated system, will rarely produce enough power to cover all day usage AND export a meaningful amount of excess power. As a solar system feeds the houses immediate needs as a priority and then exports remaining excess.

The premium feed-in could be double, say $1.00, even $10 (not just a generous $0.44c), and it still wouldn’t be much benefit for most homes these days, because if you're not exporting anything, zero kilowatt hours multiplied by $1 is still $0.

When do i need to replace or upgrade my current solar system?

Whenever your system can no longer adequately meet your needs or an upgrade/replacement becomes cheaper than the alternative.

If you are experiencing significant electricity bills, you should speak further with an expert about your options.

It doesn't hurt to get an update.

Will I lose my premium feed-in tariff?

Every premium feed-in will end at some point, if it hasn’t already. 

In short, you will lose a PFIT when you upgrade or decommission a system with a PFIT, but can keep it if you are just fixing or replacing it.

Pylon Solar Tool

What is Pylon?

Pylon is an industry leading solar design tool that uses crisp, up to date high resolution imagery of your property and intricately calculated models that map the sun’s position, and travel path every day of the year. Think Google Maps, but in 4k, with laser guided rulers and intuitive features that are hard to fault.

This eliminates nearly all the guesswork and delivers millimeter accurate precision directly for our consultants, when evaluating and considering a recommendation with you. It is so accurate, if we were at your property today, we would STILL use our custom design and savings calculation tools, right there in your living room.

The software allows us to properly assess the site from all angles, at all times of the year. By making these calculations, we are able to confidently provide you with these savings figures and instantly back this up in writing inside a proposal that we are bound to deliver on.

What is the savings charts?

Savings charts generated by Pylon is based on the long-term savings your specific solar system will produce. 

For example, this life-time chart shows the estimated energy bills before going solar (grey line), and the estimated energy bills after having solar installed (blue line). Using these figures, we are able to give an accurate estimate of how much you will actually save going solar.

Pylon is also able to give us a monthly comparison, taking into account seasons that affect solar production and electricity bills. We are able to take these figures to give you an accurate representation of solar savings.

What is self-consumption?

The solar power that's generated on your roof can be used immediately or exported to the grid. Self-consumption is when you use it yourself rather than exporting to the grid.

When we specify a percentage of self-consumption in our Pylon projects, for example, 40%, this means 40% of the solar power is used by the home immediately and 60% is exported to the grid. These numbers are used to calculate financial outcomes and savings for your proposal.

We typically see a 40% self-consumption usage for most residential homes, however, this is altered on a customer-by-customer basis.

What is the energy profile chart?

Based on the data and information about how our customers use energy on a day-to-day basis, we are able to use this to create energy profile charts within Pylon. These charts will show the interactions between the solar energy produced by the solar PV system and the energy load of the household. Pylon’s clever calculations also take into account real-world conditions such as weather, so these figures are quite representative and accurate.

How do I read the production chart?

We use Pylon to calculate your system’s production which uses typical meterological year (TMY) data for your address, and also takes into account the design and layout of your solar PV system such as the tilt or azimuth of your panels.

Pylon uses TMY data which is much more accurate than using the average climate taken from previous years. TMY data uses “typical” years representative of the weather and climate in your region. 

The monthly total chart shows the total amount of energy produced in each month in a typical year. Whereas the daily average chart shows the average energy production of each day in a particular month.

What is the discounted payback period, return on investment, net present value and internal rate of return?

Discounted payback period (DPP) is the payback period or how long it will take for your solar savings to pay off when also accounting for factors such as inflation. As this figure also takes into account inflation and recognises the time value of money, it is more accurate than a simple payback period figure.

Return on investment (ROI) is the gain of the investment relative to its cost. For example, a system with a 150% ROI means your initial investment plus half again will be returned to you.

Net present value (NPV) is the difference of the sum of all the future savings from your solar system and the initial investment. Future savings are adjusted for today’s value of money and hence it is the “present” value. If the NPV is above $0, then that means it is a good investment as your future savings are worth more than the initial expense or investment. 

Internal rate of return (IRR) is the discount rate or the interest rate that makes the NPV of future cash flows equal to 0. In other words, it is the interest rate that we can expect our solar PV system to give when you invest into it.