Oversizing your solar array

Oversizing your solar array

Oversizing your solar array in comparison to the size of your solar inverter can be a great way to generate the most kWh from your solar power system at the best price. It sounds counterintuitive when you first hear it; installing a 6.5kW solar array on a 5kW inverter seems like an inefficient way to design a solar system, but rather than using the term oversizing, I’d suggest it’s more like optimising or supersizing your system. There are boundaries and limits to how far you can go, but in many cases I think it can be a good idea.

Firstly I must mention that this isn’t appropriate with all solar inverters, so before you do anything, check with the inverter manufacturer (or your local solar installer) to make sure their inverters are designed to cope with oversizing your solar array. Green Energy Options has experience in oversizing solar arrays and can advise of which inverters are most appropriate.

Why Oversize?

The price of Photovoltaic (PV) solar modules has dropped dramatically over the last few years, so it is now much cheaper to add additional solar array capacity. The idea is that rather than putting money into additional inverter capacity put your dollars into extra panels and you’ll see a better energy harvest and better financial result.

To explain why, I’ll start with the nameplate rating of a solar PV panel; a 260 Watt panel for example is a power output that’s achieved in a lab under Standard Test Conditions (STC) that is at 25 degrees Celsius and 1000W/m2 of irradiance. In reality the panel will rarely put out 260W of power because of system losses. For much of the time the panel’s operating temperature will be more like 40-65 degrees and heat inhibits the panel’s output a little, cloud cover can also mean the system won’t be performing at i’s peak or the angle of the sun in relation to the panel can contribute to a reduced output. We also need to bear in mind that over time the silicon in the module will degrade and dirt and dust build up can reduce output too.  Under these circumstances where a solar panel or a solar array isn’t performing at its peak output very often, the top end of the inverter’s output range is rarely used.

Oversizing Enphase micro-inverters

Enphase Energy recommends oversizing panels in relation to their micro-inverters, they recommend using panels up to 270 Watts on their 215 Watt micro-inverter. Below they show in a graph that the losses from ‘inverter clipping’ are mostly below 0.5% (when the panel output is above the peak inverter capacity). This is by far outweighed by the additional production that you get from having a larger panel, up to 12% increased output. In essence the same theory goes for larger string inverters too; Fronius state that their Galvo range of inverters can be oversized by 100% of the inverters nameplate capacity, as long as other conditions are met and their warranty is still upheld.

Enphase Oversizing Graph


Clean Energy Council Guidelines

One thing that needs to be kept in mind is the Clean Energy Council’s (CEC) design and installation guidelines, where they state that ‘In order to facilitate the efficient design of PV systems the inverter nominal AC power output cannot be less than 75% of the array peak power and it shall not be outside the inverter manufacturer’s maximum allowable array size specifications.’ In other words the array size cannot be more than 133% of the nominal inverter power rating.

Powercor is the electricity distributor for Western Victoria, this includes Geelong, the Surfcoast, Bellarine and some western suburbs of Melbourne. Powercor have a 5kW inverter limit for single phase connections. In a scenario, where you are a high energy consumer and would like to install a larger solar array to maximise the benefit of your solar system, we can theoretically oversize your solar array to 133% or 6.65kW and still be within the CEC guidelines.

Analysing Costs

An analysis done by our Friends at AC Solar Warehouse show that a high quality 260W solar module paired with an Enphase M215 micro-inverter (peak output 225 Watts), would see clipping of 0.01125kWh on the best day of the year. They went on to say that there was approximately 12 weeks of the year that saw some clipping and that this worked out to be about 0.987kWh of lost production. Offsetting at $0.30c/kWh it works out to be a loss of 29.6 cents per module. This amount is pretty small, particularly when you way up the alternative cost of a larger capacity inverter, there’s no benefit in selecting micro-inverters that increase the cost of the system by $30 per module, in order to harvest an extra 29.6 cents per year. That’s a 100 year payback.

Oversizing and inverter life

Just one final note, oversizing your solar array means that the inverter will be running at its peak output for a larger portion of its life. This can cause components to heat up and run hotter and in some cases have a shorter life expectancy. The good news is that many inverters have systems in place to manage excessive heat build-up and protect heat sensitive components; most will even shut themselves down in extreme cases. Good inverter placement allowing appropriate cooling and ventilation can help to optimise inverter life expectancy, talk to your solar installer about the best place to position your inverter.

For any questions about optimising, supersizing or oversizing your solar array please feel free to give us a call on 1300 931 929.

Aaron Lewtas

Green Energy Options






5 Ways to Improve Solar Self Consumption

When it comes to installing a solar power system, solar self consumption is the name of the game these days. With Victoria adjusting its Feed in Tariff (FIT) to 6.2 cents/kWh on January 1st there’s not a lot of incentive to export your freshly harvested sunshine energy back into the grid, just so your electricity retailer can mark it up and sell it to your neighbour. From an economic point of view, it’s much better to consume that sun power on site and offset the cost of you having to purchase electricity from the grid at 25-30+ cents/kWh.

If you are a home or business consuming electricity during daylight hours and can self-consume all the solar energy spilling off your roof, it’s great, you can get good value from a solar power system and you might pay your system off in 4-5 years. If not you may be exposed to exporting a larger portion of your solar electricity at a low rate, pushing out your payback period.

There are a few things that you can do to increase solar self consumption from your solar power system. They range from no-cost behavioral change to energy management options and more expensive battery storage solutions. Here’s five ways you can improve your financial return on your solar system by optimising self-consumption from your rooftop.

  1. Change the times when you use electricity

The no-cost way to maximise consumption of your solar energy generation is to change the times that you use appliances. If you are able to modify your electricity consumption patterns so that you are consuming more electricity during the middle of the day when the sun is shining, you will help to minimise your solar export. Offsetting at 30c/kWh is better than exporting at 6c/kWh. Remember this is not an exact science and it won’t work for all households or all appliances, but if you can turn your dishwasher on at lunchtime, do the washing during the middle of the day or turn the air conditioner on when the sun’s out, it will be beneficial towards the financial savings you’ll get from your solar system. What I always say to our customers is “don’t turn your life upside down for your solar system, just be aware of how it operates and take advantage of it where you can”.

  1. Use a timer

Installing a timer can be a good low cost way to co-ordinate appliances to come on during daylight hours. Obviously it won’t work for all appliances, but pool or spa pumps, water pumps, and in some cases even heaters or hot water systems can be put on a timer so that their time of operation coincides with solar production. Some appliances like dishwashers and washing machines will even have a built in timer that will allow you to program when they come on. Again this isn’t the perfect solution, because if it is overcast and your solar system isn’t producing a lot of power and your pool pump is running, you will be purchasing the excess power from the grid probably at peak rate. But if your pool pump was running on peak rate anyway, it’s going to be better to have it more closely matching with solar generation times. If an appliance was running on an off-peak rate there’s probably a deeper analysis required.

  1. Solar inverter with energy management relay

Some inverters are now incorporating smart energy management functions in them that allow for optimised solar self consumption of your solar energy. Austrian inverter manufacturer, Fronius is one company that has been leading the charge here. They have integrated an energy management relay into their new range of inverters the Fronius Glavo and Fronius Symo.

Fronius Galvo Solar inverter

Fronius Galvo Solar inverter

The energy management relay inside the Fonius inverter can divert solar power to a specific appliance and help avoid exporting at a low feed in tariff. All we need to do is set a power value of say 2000 Watts and once your solar starts generating more than the pre-set amount, it will flick a switch and turn on your pool pump to soak up the solar generation. A second pre-set amount can be set e.g. 1800 Watts and when then solar drops below that point the inverter deactivates the power to the pool pump. This can be a great feature at no additional cost, but it also has its limits, similar to the timer solution, if the solar inverter is putting out 2200 Watts and there are other electrical appliances being used in the house on top of the pool pump consumption, you may find that you have a total power consumption of 3000 Watts for example. This would mean that the additional 800 Watts that wasn’t being supplied from solar would be purchased from the grid at peak rate. Once again one thing that needs to be looked at is the benefit of reducing export at a low rate, verses, buying electricity from the grid at peak rate that may have been previously purchased at off-peak rate.

  1. Third Party Energy Management Options

There are a number of new products coming out that allow you to have a bit more control over how much electricity you are importing and exporting. We expect to see many more hardware and software solutions hitting the market over the next few years that look specifically at this area. The immerSUN and ASM SunnyMate are two products that are currently available that look mainly at dealing with your hot water requirements.

immerSUN Solar Energy Management Device

immerSUN Solar Energy Management Device

Rather than just flicking a switch when the solar output reaches a certain point, these devices measure when you start to export electricity to the grid and will turn your electric hot water heater on to soak up any excess solar power, rather than having it exported to the grid for nix. In the case of an electric hot water unit, there are a couple of important factors to consider that are a little different from most other appliances. Firstly they are normally being run on off-peak electricity commonly around 15c/kWh around the Geelong region, and secondly the elements can range from 2400W -3600W quite a high power requirement. By using the immerSUN device you maximise the amount of self-consumed electricity by diverting solar to the hot water element, offsetting the cost of paying off-peak rates (if you had powered it from the grid at night), but at the same time the device minimises the electricity you have to purchase at peak rates to supply power to the hot water service during the day. The immerSUN actually has three outputs, allowing you to control two resistive loads like heaters or hot water units and one multifunction relay, which could be used to drive a pump for example.

The cost of having these units installed is starting to get a bit more expensive than the previous solutions, probably up around the $800-$1200 mark, so this isn’t going to be for everyone. As a general rule, the larger the disparity between your off-peak rate and the solar feed in a rate the bigger your savings will be. For example, an average electric hot water service takes about 8kWh to heat. Here’s a possible scenario:

Feed in Tariff = 6.2 cents/kWh

Off-peak tariff = 15 cents/kWh

Difference = 8.8 cents/kWh


8.6 cents x 8kWh (energy to heat hot water) = 70.4c/day savings

70.4 cents x 365 days = $256.96 per/yr savings

This case gives a 3-5 year payback on the unit, so could be a good solution to save money. This example does assume that there is enough solar power to heat your hot water unit each day, this is quite possible with a 5kW solar array, although there may be some boosting required from off-peak mains grid required on days of low production, which may reduce the savings a little. If the difference between your off-peak tariff and feed in tariff is less, then the savings seen will also be less.

  1. Battery Storage Solutions

There has been a lot of interest in grid-battery storage solutions for grid-connect solar systems lately. There are heaps of new products coming onto the market and costs are expected to come down over the coming years. Batteries can be another way that you can increase your solar self consumption. Rather than sending that power back to the grid at a low feed-in rate, store it in your batteries and use it at night. The technology is available to do this now and more and more people are beginning to take this option up. When compared to the other options listed above, there’s a bit of a price jump. Most decent battery storage solutions will add $13,000-$20,000+ to the cost of a solar system, depending on the amount of storage capacity you are looking for and the quality of the system, but with people getting fed up with being treated badly by their electrical retailer and not getting paid much for their solar export, batteries are a solution that many Australians are looking towards to gain more energy independence.

Battery storage solutions for solar self-consumption

Battery storage solutions for solar self-consumption

As I said earlier self-consumption is important when it comes to solar power. Many people have been ill advised about the savings that they will see from their solar system, mainly due to a misunderstanding about how the feed in tariff works. That’s why it’s important to do your research and get good advice about system sizing. Oversizing your solar system may just lead to additional exports and at 6.2c/kWh it might be better to go for a slightly smaller solar array and keep some cash in your pocket. Alternately if you are able to optimise your self-consumption efficiently through the solutions described above, you’ll be able to squeeze more value out of your solar system and keep more dollars in your pocket. Smart new technologies are set to change the way we use energy into the future, whether it be solar power, energy management solutions or the integration of electric cars into our electricity network, we are in for an exciting period – I think you can expect to see our energy network revolutionised over the next 10 years.

Note that for those solar consumers that installed their systems under the Premium Feed in Tariff or Transitional Feed in Tariff for solar, the above scenarios will not be relevant. If your feed in tariff is higher than what you are paying for electricity you will see a larger savings by exporting electricity to the grid than self consuming.

For advice on solar power, energy efficiency or anything outlined in the post above, please feel free to give us a call on 1300 931 929.

Solar Panels and Shade

Shading can have a big effect on the performance of your solar power system. The amount of shading and the time of day may determine whether it is worthwhile putting solar panels on at all. Small amounts of shading at the start and end of the day may have minimal effects on output due to the losses being imposed on a reduced initial output. Ideally you want to have clear access to sunlight during the middle of the day between 9am to 5pm. Clouds will reduce the output of your solar system, but the panels will still receive dispersed light, its direct shading from trees, vent pipes and other objects that are of most concern.

Below is an example of electricity flow in a solar panel affected by shading.

The best way to assess the impact of solar on your rooftop is to have a shade analysis done. Green Energy Options use a SunEye to assess the impact of shade on your rooftop. The SunEye is a professional tool that takes a photograph of the surrounding objects through a fish eye lens, it then lays a sun path chart across the image showing the time of day and time of year that shading affects the location being assessed. The impact of shading for each month of the year is then calculated. We include the shading report in our estimates on your solar system’s output giving you an indication on how we expect your system to perform. Generally once you get above 10-20% of shading you need to consider if the solar system is going to have the effect that you intended, our aim is to put you in a position where you can make an informed decision.


SunEye Shade analysis

SunEye Shade analysis

It is important to be aware that in a standard solar system with a string inverter and 10 panels, shading on one panel can have a “weakest link” effect on the rest of the array, reducing the output of the whole string of 10. One option for reducing the impact of shading is to use micro-inverters. Micro-inverters individually optimise the output of each solar panel, so that shading on one panel doesn’t affect the output of its neighbors.


Shading micro-inverter vs string inverter

Shading micro-inverter vs string inverter

Image courtesy of Greenstar Micro-inverters

Green Energy Options can provide a detailed shade analysis of your site as well as options for both string and micro inverters. Give us a call to find out how you can go solar 1300 931 929.


Solar panel orientation

Which is the best direction to point your solar panels?

It’s an interesting question and you would think the answer is pretty simple – NORTH.

In many cases you’d be right, a north facing solar array will generate more electricity than an array that faces east, west or south. In Geelong, putting panels on an east or west roof will normally result in a loss of around 15%, compared with a north facing array on a 30 degree pitch. Many people are surprised by how small this loss is and it certainly doesn’t rule out these options. It’s  recommended however to steer away from south facing panels where possible, where losses are in the range of 30-40% on a standard home’s roof pitch.

Solar panel oreintation

With the introduction of lower feed in tariff (FIT) rates for your solar electricity that’s exported to the grid, an interesting discussion about solar panel orientation has come about. Should we be facing our panels west?

Sure a north facing array generates more electricity than one that faces west, but it generates the peak of it’s generation for the home in the middle of the day. For the average working family that has a low electricity consumption during the day it could mean that a lot of the electricity generated is being exported to the grid at the current FIT rate of 8c/kWh. The theory is, that if you were to face your panels west, they would generate more electricity later in the day, when you are more likely to be using the power. In this case you would be able to offset the cost of buying electricity from the grid at the going rate (often over 30c/kWh), which is more valuable to you. This is true particularly in summer when solar production is higher and the daylight hours are longer extending into dinner times.

Another related argument for pointing panels west comes from a Renew Economy article where Adam McHugh, a lecturer in energy economics and energy policy at Murdoch University, where he suggests that pointing solar panels west, would correlate the systems output with times of peak demand on summer afternoons. On hot sunny days when everyone turns their air conditioners on, west facing solar panels would be producing electricity. West facing solar has the potential to compete with the distribution network and expensive peak generators by reducing the cost of supplying electricity particularly during peak demand events.

The orientation of your roof and available space may be the deciding factor in the end, but it’s good to know that there are normally a couple of options. A good solar installer will give you a comprehensive analysis of your solar systems production as part of your quote. This should show average daily kWh estimates broken down monthly and for the year based on your roofs orientation and pitch.

For more info on panel orientation or the potential of you roof give Green Energy Options a call on 1300 931 929.

Six Solar Tips

Six solar tips to consider when buying a solar power system

There’s a lot of information out there in solar la la land and if you are new to solar, it can be tricky to sort through and find the answers you need. I’ve put together a list of six solar tips to help give you a good start on things to consider when buying a solar power system. Here we go…

1. Find out who manufactures the solar panels and inverter.

Do your research. Does the brand have a good name? What have other people’s experiences been like? Some companies are reluctant to give you this information and some are using cheap rebranded or “lucky dragon” panels which have only been on the market a couple of years and substitution of lower grade materials is not unheard of. Choose an installer that is transparent about the components they use and stick with well-known brands that have an Australian office for warranty issues.

2. Make sure you’re happy with the installation company.

Who are they? Are they close to you? What have others said about their service? Are they members of any industry bodies Clean Energy Council (CEC), Australian Solar Council (ASC), Solar Energy Industries Association (SEIA) or the Alternate Technology Association (ATA)? There are a lot of solar installer reviews online if you want to find feedback. Also watch out for the hard sell sales tactics, steer away from anyone trying to get you to make your mind up on the spot.

3.      Don’t buy the cheapest solar system you can find.

Obviously price comes into the equation at some point when you are buying a solar system, but like anything, you get what you pay for. There are many ways to cut costs in a solar business, I could purchase the cheapest panels/inverters that I could find, I could squeeze my installers on the installation cost, buy cheaper isolators, cabling or other balance of system components, or I could skimp on the resources I put towards customer service and post installation backup. Either way, by compromising on the above things you may find you end up with a less than average solar system or less than average solar experience. You don’t have to buy the most expensive option to get a good system, but don’t buy the cheapest!

Ballarat Solar Installation

Ballarat Solar Installation

 4.      Don’t compromise on the inverter.

50% of all system failures have something to do with the inverter. There are heaps of cheap options out there now, often at less than half the cost of the good stuff. Our suggestion is, it’s not worth it, buy a good quality inverter – some examples include SMA, Aurora or Xantrex. If your panels are going to last 25 years+ you don’t want to have to replace an inverter every five years. There are also some fantastic micro-inverter options becoming available, these generally come with stronger warranty periods, better system monitoring and safety and performance benefits.

 5.      Take your warranty with a grain of salt.

Although warranties are an important aspect of buying a system  nearly all panels on the market have a 25 year performance guarantee, stating that the silicon will degrade at a certain rate over time, with the panel still producing a minimum of 80% of its initial output after 25yrs. Note that the panels also have a materials and workmanship warranty normally in the range of 5-10 years. Inverter warranties are normally between 5-10 years with some micro-inverters offering up to 25 years. Then there’s you installation warranty from the installer which usually is 2-5 years. The one thing to be aware of here is that the warranty is only as good as the company behind it, if they go into liquidation or are taken over by another business, you might find yourself left high and dry. Some big panel manufacturers and installation companies have gone bust or dropped out of the solar industry recently, so be careful. Our best advice is to read the fine print, stick with good quality components to minimise the need for warranty claims and go with a company that has a track record and you feel you can trust.

 6.      Size the system to cover your daytime usage.

In Victoria, the Feed in Tariff is now a minimum of 8 cents per kWh. The price you are paying for electricity is probably up around 30 cents kWh. This means you don’t want to oversize your system too much, as you won’t be paid very much for the excess power that you’re not using directly and exporting back to the grid. If you size your system right, you will get a better return on investment and quicker payback period. If you need some help here we can give you some advice. Note that there is currently a great niche for many businesses that use power during the day to capitalise on the benefits of solar power.

I hope the tips help. If you have any further questions, or are after some advice please feel free to give us a call on 1300 931 929.

Cheers Aaron.

Solar power misconceptions

I thought I’d start off by explaining a couple of simple points about how solar panels work, hopefully clearing up a couple of general misconceptions about solar.

1. Is there enough sunlight in Victoria to make solar panels work?

I guess it depends on what your expectations are but generally, YES there is plenty of sunlight in Victoria to make solar work. If you compare the amount of solar radiation we get here, to say, Germany – the worlds leader in solar power installations, we get around 30-40% more sunlight.

2. Isn’t it too cold here for solar power here?

Photovoltaic solar panels produce electricity from light, not heat. The photovoltaic material in the solar panel (normally silicon) tuns the light energy into electrical energy, the more sunlight the better the performance of your solar system. In fact you will find that as it gets hotter, the output from your solar system will drop off slightly, this depends on your solar panels temperature coefficient, but I will talk in more detail about this in a future post.

3. I don’t have a north facing roof, it’s not worth going solar. 

This isn’t necessarily the case. Yes, a north facing roof is ideal for optimum performance, but you will find that even going around to an east or west orientation will generally only lose you around 15% compared to an optimum pitched north facing roof. There may even be options to split your system across a couple of different orientation rooves, if half your panels are north and half are west, you may end up with only a 7% loss over the whole system, which normally isn’t too bad. The Tindo Karra solar panels tend to be particularly suited to these scenarios, the embedded micro-inverter gives your system more flexibility when positioning panels, allowing you to split them up easily over a number of different rooves.

Green Energy Options aim to give you the information you need to make an informed decision. We can give you advice on panel positioning, estimates on electricity generation and money saved based on the panel positioning and let you decide if it’s going to be worth while going ahead.

Hope you enjoyed our first blog post, keep an eye out and we’ll try an keep you posted with useful tips and updates about solar power.