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How Many Solar Panels Do I Need To Power My Home?

Many solar panels on the same roof

One of the most common questions people have before investing in solar is how many panels they need.

The simplest way to find this out is to ask an expert installer. They will likely conduct a consultation and provide you with a quote based on your energy needs.

As a rough guide, a house with one or two people will likely need a 1.5kW system. A household with up to three people and a few fancy appliances may need 3kW. While a big family will probably need a 5kW system.

But this all depends on the type and number of appliances you use, the expected output of the panels, where the panels are located, and how they are oriented on the roof. With so many variables, it really is worth consulting an expert solar installer to determine how many panels you need.

Alternatively, if you’re mathematically inclined, you can attempt the estimate yourself. To do this, you need to figure out your average daily use of power.

You can probably find this on your most recent bill. If it only shows your yearly use, simply divide this number by 365 to get a daily average. For example, let’s assume your yearly use is 5,000 kilowatt hours (kWh). Divide this by 365 to get a 13.7 kWh daily average.

Whatever way you use to determine your needs, it’s best to build in a buffer. Solar panels don’t work at 100 percent efficiency. There will be times when their output is reduced. So add a little extra – say another 25 percent. To do this, multiply the daily average by 1.25. Using the example above, this comes to 17.1 kWh.

You also need to take into account the amount of sunshine your home receives. While Australia is mostly sunny – and receives more solar energy than any other continent – some parts are shadier than others. Ask your installer or local solar authority about the amount of sunlight you can expect to receive on your roof.

You then need to divide your daily average by the number of daylight hours. This figure will tell you how many kilowatts are needed each hour by your panels to absorb solar energy. Let’s assume your suburb receives 6 hours of daylight. Divide 17.1 by 6 to get 2.85 kW needed every hour. Times that by 1,000 to convert the sum into 2,854 watts.

These system sizes allowed you to run your home on solar as much as possible while minimising the wasted electricity sent back to the grid.

We asked Stephen Jenkins, a homeowner on Central Coast and proud solar owner since May 2017 to share his energy bills with us before and after installing a 5kW solar system. Some data on the bills below have been blurred due to privacy reasons.

  Bill from 2017 Bill from 2018  

Unfortunately, you can only save
on power you use during the day

This is frustrating for many people, especially if you have a full-time job. You end up getting free energy during the day, but you aren’t able to use it.

Thankfully, these limitations have now been overcome by modern solar battery storage technology. Homeowners can now save money no matter when they use their appliances

Let me explain...

Cut your electricity bills with
modern solar battery systems

Although solar battery systems have been around for years, they were cumbersome, expensive and a poor investment. Unless you lived in the remote outback without a grid connection, they didn't’ make sense.

But new technology breakthroughs have changed all that…

The newest batteries can economically store the electricity generated by solar panels during the day… so that you can still benefit from free energy even if you are only at home after dark.

Here’s how they work...

  • Solar panels convert sunlight to DC (Direct Current) electricity
  • Any surplus DC electricity charges the solar battery.
  • When the sun sets and the panels stop working, the battery powers your home.

At night, you can run your dishwasher, watch TV, or charge your phone without paying for power.

It’s no wonder thousands of Australian homeowners
are itching to install these battery systems as soon as they can.

The current leader in the solar storage market is the Tesla Powerwall 2.

The Tesla Powerwall 2 has twice the storage capacity of the original Powerwall - 13.2kWh. This is enough to power most homes after dark, so you can cut your bill significantly.

Not only that, the Tesla Powerwall 2 is beautifully designed. It is streamlined, sleek and stylish. Plus, it is rated for indoor or outdoor use in the harsh Australian climate.

It is also very safe. There are no live wires or unsightly vents - and the lithium ion battery requires minimum maintenance.

You can even monitor your electricity usage from your iPhone or Android device!

Plus, if you need additional capacity, you can connect nine Tesla Powerwall 2 units together. This is great if you want to power your home during blackouts or on overcast days.

How much can you save with a Tesla Powerwall 2?

It varies.

The amount of money you can save will depend on your actual individual circumstances.

However, case studies suggest you could reduce your mains grid electricity consumption by as much as 80% with a solar + battery system. This is based on standard system installation in a state capital.

The upfront costs are variable too, but it is possible to get the system installed for as little as $35 a week on an interest free loan.

These savings are based on existing government incentives, which may disappear at any time, so if you are thinking about solar storage, don’t delay.

​Click here to discover how much you can save with batteries now

59 comments so far

  • Federico Nina 3 years ago

    My home is 1200 square feet,in a open and cleared place,I will like to do solar panels;we have regular applying :small microwave,small air condition for the bedroom, 2 pedestals fans,a blender or magic bullet,2 laptop computer a 45 inch

  • Raymo Mlambo 3 years ago

    Please i need you help I use power of solar system in my house i ha a fridge radio 3 tv 3 fan so how man solar panel how man battery size of charge control

  • ritesh pratap 4 years ago

    Solar panel upgrade needed.Have 8 by 190 W panels but need a new smart inverter to go up to 3.0 kW.Got roof space but facing west or east.Northside has the 8 panels.

  • Geoff Grimley 4 years ago

    We are looking for the most economal power supply, we have two solar systems, a 1.5kw & 2kw systems. Our house is fully electric, including pool pumps, three fridges, air conditioning, looking at reducing our last bill with Energy Australia, we have been with this company for 20 years.

  • Solar Panels Las Vegas 5 years ago

    Solar Energy is the best way to beat rising our electricity costs. However, Even at this stage Solar Panels are still very expensive and especially in states or region where government is not support or subsidizing the cost its impossible for low or mid level income group people to buy this expensive at once.But I believe Solar Energy is going to be future for homeowners and business owners.

  • Cohen Jacobson 6 years ago

    Hey thanks for sharing this really helpful info. Do you have a link for some different providers for solar panels? I'm still kind of unsure whether or not this would be a good investment, or rather, if I can afford this investment. I've been hearing great things about a sort of ROI with solar panels and I wanted to find out more. Thanks again!

  • Ian Blair 6 years ago

    One thing all these calculations seem to forget is that the panels do not produce full power while there is light. it will be at a maximum in the middle of the day with no cloud providing they are pointing in the right direction . Either side of this it will be less. Also if there is cloud. At today's net feed tariff the best direction is to face them west to get as much of your own produced power when the peak electricity rate on you meter is at 40cents in afternoon and try to generate your own power then. and forget about the other times.

  • Beldengi 6 years ago

    I run my tiny house via an off grid system consisting of a single 85W panel and a generator which I limit to $10 a week in petrol. The panel runs my lights (one at a time ), my fridge for about 6 hours a day ( you dont need a fridge on at night ), grinds my coffee, charges phone and computer tablet, and the generator cuts my wood for cooking outdoors, and runs fridge, tv, fan, stereo for 3 or 4 hours a night. I have been living like this for 8 years.

  • Peter 6 years ago

    To answer the battery question you must use the very big dedicated 2v solar batteries, They last over 15 years truck type batteries just don't stand up. You don't need light batteries for solar like you do in motor vehicles The solar batteries have very heavy thick plates to make them last. They are also easier to build Just the amount of lead adds up the price and freight cost due to weight

  • Bob 6 years ago

    The only problem with the above panel estimation is that many electricity suppliers have a maximum array size that is permissible on their network, For example I am with SP Ausnet in Victoria and the maximum array allowed is 5kW.

  • jmes 6 years ago

    Phil Bramly... The problem with off grid storage is the cost of replacing worn out batteries is more expensive than paying for on grid electricity. To put some figures on it, A 100Ahr deep cycle 12v battery costs around $200 for (12x100)1.2kWhrs. You would need a couple days of back up power during winter for the no sun days. If you use 20kWhr's per day you would want atleast 40kWhr's of storage. 40 / 1.2= 33.3. It would be a 48v system so you would need the batteries in 4's. So you have to go 36 batteries. 36x$200=$7200 worth of batteries. Each battery would need to be replaced every3 years as they are constantly being charged and discharged. That's 7200/3= $2400 a year in battery replacements and thats not taking into cosideration the initial construction costs.

  • Phil Bramley 7 years ago

    The solution here is "off-grid"! No more power bills. The major drawback to everyone going "off-grid" is battery storage technology but having said that exciting developments are in the labs as we speak. When the battery storage issue is solved or improved anyone left "on-grid" is paying for power unnecessarily!

  • Richard 7 years ago

    It's not the panels you have to worry about, it's the inverter & batteries. If you buy the panels alone like Anna Mortimore made the mistake of doing, you either use it immediately or lose it. To store the electricity generated by the sun and the tradesman-installed solar panels, you need special batteries and inverter which cannot possibly last long enough for you to get your money back even! I prefer to ask this: How many solar retailers have failed - answer: Just bout all of them are in dire straits financially. How much money did & do the so-called green power companies donate to the greens and labor parties to get such monumental political backing? Nixon proposed the same thing to congress in 1970 and everyone said he was a loon! The technology was not there then and it is not here now. That's the facts. CO2 is food for plants. Let them feast!!!

  • Clive johnson 7 years ago

    This clearly written article, along with some very informative comments, have left me wondering if it would be prudent to wait for the next generation of solar panels before taking the plunge.

  • Bill Dielenberg 7 years ago

    Start with a minimum of six panels. As sure as night follows day your electricity bill will drop considerably (depending on the feed back tarrif) The more panels you have the greater the reduction of you bill. There is no need to be too technical.

  • John Shaw 7 years ago

    There are two of us in the household and we are retired living in Perth. We had a 3KW 12 panel solar systems installed in January 2014. Depending on the time of the year our solar panels produce between 10 to 17 power units per day and this is over a 5 to 7 hour time period. Ironically less is power is produced per day during the hot, hot Perth summer months. Any power used after the 5 to 7 hour solar generation period and the remainder of the day is a the full tariff rate. Initially excess solar power feed back into the Perth power grid was given as a credit in excess of 40 cents a unit and from memory the power tariff rate was 11 to 12 cents per unit. Obviously this rebate arrangement was and is not sustainable. I am disappointed at the savings made to date and it is doubtful if the solar panels will pay for themselves during out lifetime. What is needed to make solar panels more viable is for an economical system to be developed to store the excess solar power produced so that it can be feed back in to the household grid.

  • Joe 7 years ago

    The governments are considering getting rid of feed in tariffs altogether for new installations which means that unless you use all your power during the day (when the solar power is generated) or have a battery - most of the power you generate will be going back to the grid.

  • sparky 7 years ago

    You can buy a solar system just don't hook it up to the main power grid for fucksake. You really think the power company is going to throw away profit? Unlimited free energy? Yeah when we stop paying taxes and quit working like slaves to pay our mortgages to illegal banking cartels. Not to mention you can make your own electricity using two magnets and a bit of copper wiring for virtually nothing.

  • Jorge 7 years ago

    I think you people that are complaining didn't do any research before purchasing Obviously cheap panels and inverters were used !!! I have a 6kw system using Canadian Solar panels and Schneider inverter and I average 29kwh per day since this system has been on I don't have a bill and my system will pay for itself in 2.5 years !!!

  • Stacia 7 years ago

    I live alone and have 5 panels which is sufficient for me... when I have guests it uses more... I am still ahead... In the winter the most I pay is $49 as I use the electric heater... otherwise, the other quarterly bills are always in credit to about $55. My cooking and hws is gas... All my family and most of my friends have solar panels and it's the best thing we ever did. Western Australia has a horror Liberal premier who believes in slogging the consumers with ever increasing prices.

  • Wade 7 years ago

    We had to fight really hard to get above the 5 KW system and only threat of litigation were we able to raise it to 8.6 KW. We installed three 2 KW heaters for the winter so we did not have to use gas as much and we run then only during the day. The aircon is run all summer and the panels reduce the heat on the house also. Our power bills were 1200 a quarter and now would be 1500 a quarter. We have reduced that to $351 this quarter and next quarter we expect no more costs than $150-200 for the quarter. The grid controllers try to reduce the power of the panels to 5KW or less and they use the voltage rise at 1 % to limit the systems installed. You have to fight but it is worthwhile.

  • Christina Scott. 7 years ago

    Please all keep an eye on your box that shows the rates flicking away daily. I am one person and 3 accounts ago I received a bill for over $200.,at the time thought it was too high. However they had been paying me back outstanding moneys for the pensioner rebate and I wasn't registered. Account was in credit. Then second account arrived and it was higher than the last so decided to start checking and contacted the Company it was then established that my box had died. The Company that installed the box and panels took back the box and it took another 4 weeks for it to be returned, as it had to go to SA My up to date account has arrived and it is over $220. I now have to keep contacting the Company that installed . the box and endeavour to get the rebate they have promised because of the problem of the box being faulty. I might also add I am one of the original 44cents recipients. Keeping an eye on situation as it appears in the not too distant future there will be a reduction on the 44cents. I blame the Governments for the heavy sell in the first place as all of us who forked out the cash to install the panels were encouragd to do so to help the grid etc.Now a slap in the face may well occur. I add that at the tijme of installation my husband was alive and an Electrician to boot and he could see the benefit for the power grid and also the reducing of our account. Little bit like the home batts furore.

  • Iasn Wells 7 years ago

    what a joke solar power is, i produce at the moment 28Kwh per day, but I only use a little of it while the sun shines, as most people do. But between 1600 and 0600 the next day I pay for power at 30c/kwh, But they pay me 6c/kwh for my excess each day , about 20 kwh Solar power is a joke unless you can have about 36Kwh of battery storage

  • David Elwin 7 years ago

    I am currently planning the feasibility of setting up a small manufacturing plant in a remote area of central Philippines. The plant will have approx 10 machines powered by average 1/2 horsepower electric motors, operating 16 hours per day x 6 days per week, plus lighting, water pumps, computers , etc. As the local grid power supply is 'undependable' I am hoping to power the plant with solar panels with back up diesel generators; however, I am struggling to compute an indicative power usage for the plant so that I can source local supply & install quotes for the solar system, can anybody help please? Dave

  • Mil Rudic 7 years ago

    I think the most important thing you left out of the article is the fact that currently. If you go and purchase a 2kw system if you ever want to upgrade the electricity companies will set your grid rebate to zero. and currently the buyback is 0.08 cents per kilowatt, when the usage charge is around 25c per kilowatt. So if you don't have any panels at all the best idea is to buy a 5KW system which is the maximum you can put in(yes more expensive but anything less and you wont be able to add panels in the future until hybrid panel system are introduced which means storing to battery rather than to grid). then work out your usage. We made the mistake of buying a 2KW system and now cant add any more without being penalised. and 2KW is definitely not enough as our yearly usage is around 6,000 kw per year we still get bills yes better during summer than winter. But if i knew it was going to change i would have spent the extra money and got a 5KW system in the first place

  • Hanry 7 years ago

    Ask your Installer ... You jest surely ..... He's the guy out to sell you as much as he can. Go and ask someone who installed panels at least a year ago.

  • Warren in Busselton 7 years ago

    I had 12 panels installed almost 2 years ago to give me 2280watts. Feedback rate is a lousy rate of 8.6cents per unit for excess solar generation . Unless I consume power at the same time as the panels are generating in daytime and use zero power at night it is a total waste of money. I would not recommend anyone fitting them unless the power authorities pay an honest rate for generated solar power, that being the same as for power used at 29cents per unit. Don't get sucked in to paying and fitting them as they deteriorate over time and will need replacing long before you get your money worth. Solar water heating is good, my 300l unit works well for nearly every day for two people, even over winters in southwest WA. Note:- It is essential to insulate the external pipes to limit heat loss in winter as most installers neglect this.

  • Anna 7 years ago

    I have 6 solar panels and all my bills for electricity have been a small credit for every quarter since installation - installed 18 months ago. Slightly higher credit in summer as in winter I use the heating. Salesman tried to get me to put up 24 panels and I said that would be too many. Salesman tried to get me to install the panels on the front which would have ruined the look of my home and front is partially shaded by trees. Get a lot more north and west sun at the back so that is where they were installed.

  • Linda Thomas 7 years ago

    im like you Anna. I have 8 panels each with an inverter. I live in Qld, so even in winter we get lots of sun. My last bill gave me back $23.00 had to pay $550.00 bill. So disappointed. Only 2adults in this household!!

  • Peter 7 years ago

    To TIO Southwest Vic. You are not using the system to your best advantage. Use the items like dish washers, clothes washer and dryers during the day, this way you will be using your power, by running these things by night you are paying high rates to the power company while you are only getting 10 or 12 cents for your power which is produced during the day. With the rates being paid by the power companies it is not a money making project like it was 5-6 years ago, it is now a matter of using your power while the sun is shining and cutting your power usage at night to minimum. Stagger your usage, i.e. Dish washer after breakfast, clothes washer at 11am and dryer, if used, in the afternoon. This way solar will be utilised to your full advantage. Hope this helps. Peter.

  • Dieter Koppen 7 years ago

    I live in Qld, 5 years ago I paid $2000 to get 1,5 kw solar power installed. Next thing I bought a 2 burner gas stove from a camping store for $50 and don't use the elec stove any more except for the oven and griller. We try to keep down elec consumption as long as the sun shines. Our feed in tariff is c 52! I turn up the fridge in the morning and down when the sun is up. I even freeze some freezer bags over night and put them into the fridge during the day. In all years I had once a $3.5 bill, in the summer AGL pays me $100 to 150. Laughing every quarter all the way to the bank.

  • R James 7 years ago

    How many do you need? A lot more than you can afford, unless you expect other taxpayers to pay for them. Solar is expensive. Panels have a limited life, and if people have to pay full price for replacement, they're going to end up as unsightly useless blemishes on buildings in a few years. Be very aware that, one way or another, we are all paying big time for these solar systems.

  • Lito Crisostomo 7 years ago

    I don't have much space on my roof for standard sized solar panels as I have a couple of solar water panels up there. Is there any medium sized solar panels available?

  • John Stewart 7 years ago

    We installed a 26 panel system plus a hotwater solar system on the north facing roof of a 20 sq house in Central Vic 2 years ago and couldn't be happier. All these winghers and conspiracy theorists make me laugh. Just make sure you vote for a solar friendly party at the next state and federal elections, otherwise your tarriffs and rebates may be slashed by parties beholded to the dinosaur fossil fuel burning power companies. We are with a company that gives us a .33c feed in tarriff and we asked our supplier and installer to give us a system that would make us power bill neutral. Thats exactly what we got. Its not a stand alone system because I am not convinced of the reliability of the current generation batteries, but they are improving. We pay a bill in winter but this is compensated by the refund we get in the summer months. And BTW, panels last longer than 5 years. Closer to 10 particularly if you buy good quality and by then you have more than paid for them anyway.

  • Sean 7 years ago

    Agree with John. Wish all maths question were as easy as this exam though Kat. Consumers please don't ask a 'solar installer' about the benefits of solar power - They don't pay your electricity bills - they make money by selling their product and services. Exaggerating the benefits, while hiding the reality, is paramount to their success. Ask the bloke in the street, even a troll on the internet...it will make more sense. The concept of making power from that big shinny entity in the sky is awesome…problem is the consumer doesn’t harvest the benefits now. The greedy have ‘stolen’ the Sun. Financially speaking, solar power benefits in 2014, are a mythical idea based on optimal conditions, optimal equipment and not using power...when...you actually need to use power. Of course in the real world (where I live) this does not and will not occur. Anyone can use a spreadsheet and calculate usage, to the hour if you want. Soon, I will have full year of data, now that we have a smart meter. What a 'normal' family - 2 working parents and 2 school age kids use over the year. More importantly, when we use power at different times of the year. Summer versus Winter. School holiday’s versus everyone out during the day but consumer electricity when...wait for it...when the Moon is high in the sky. You can make as much power as the sun allows during the day...less the 2-3kw/h your house uses while no one is there...get paid 6 cents for it and when you get home you can buy it back from the GREEDY power companies FOR 4-5 TIMES as much...given this, how long will it take to pay back that initial cost...quick open a spreadsheet and do some maths. Don't forget to include the 'interest' if you borrow the money over 5,6,7 years...by which time, remember the panels wont be working as efficiently. So 'whingers' (I will call them ‘logical people’) don't have tunnel vision, Don....The offer of 59 cents, 44 cents or even 12 cents is long gone and we now realize what is going on and are now letting other people know before they too get ripped off. Well done to the chosen few, like yourself Don (maybe 5,000 or so similar?) - Before the government st#*t itself and removed the rebates. I am sure it is a wonderful situation for these people but for the rest of the population we are stuck with the decision of - buy power or feed the family! Meanwhile the people who benefit from solar power concept are laughing all the way to the bank. The panel maker gets his cut. The installer takes a piece of the pie, the GREEDY power companies continually count their profit and even the government takes their bit through the GST. What about me? The Sun is here to stay apparently. And as sure as it rises in the East and sets in the West, so too will the consumer continue to pay for the power it produces at a premium.

  • dog 7 years ago

    Kat 2.85 kw multiplied by 1000 would be 2850 kilo watts. I think you should divide doh

  • Christel 7 years ago

    I was told that a 3kw system would easily power my home. I live on my own in a home with split system aircon, electric hot water, cooking and appliances. Why do I still end up paying between $120 and $190 on electricity? Please be so kind and explain. I have a feed in tariff of 8c Makes me wonder if it is really worth it to install solar panels, especially if the government now plans to cut the incentive. I wanted to increase my panels to 5kw but not sure if it is a wise move.

  • Ivan Colaco 7 years ago

    Can someone tell us which are the best panels on the market (price wise, efficiency and build), also the best inverters.

  • PH 7 years ago

    Small Villa 10 Panels (North) 2.5 inverter, Does it matter if you use Washing Machine, Dishwasher etc., at night or is it better to use during the day.

  • Mike 7 years ago

    TIO, southwest vic. On your bill did you see any feed in values (KW/hrs) at all. Check you power meter, it should have a value that you have exported to the grid. If you are not seeing this on your power bill contact your retailer. Mum moved to a new house with a solar system but it took the retailer about 3 bills to catch up (and many phone calls) before the feed in kwatts made it to the bill. You should see two types of savings. a) Lower costs (this is where you used the power you created, thus did not pay for from the supplier) b) Feed in rates/exports (actual dollar value on the bill) Please note, my 5Kwatt system in south east Victoria was working perfect. But I did have some challenges (morning sun would hit a tree, and not facing 100% north). that said I did hit the peeks of 5Kwatts on good days and my output was simular to others I checked. my daily average output over 2 years was 16 KWatts/hrs per day. This output would range from less the 1 Kwatt hr on a bad day, to 38 KWatt hrs on a good day.

  • TIO, southwest vic 7 years ago

    Anna, like you we have not had a very good experience with our panels. Our system was installed 2 years ago and we paid $6000 more than the average. We were led to believe we were getting a 4 kw inverter (this was increased to a 5kw as they don't make 4's) but our panels are only for a 3 kw system. This quarter was the first time we had serious return - $64 (yes sixty four dollars for 91 days). I do my washing either weekends or late at night during off-peak and the same with the dishwasher which is usually every second day. We use approx 1518 kWh in that 91 day period. When our second bill arrived with still no reduction I rang them and was told it was working fine, I contacted them again 10 months after installation and asked them to check it as I wasn't happy also asked if I could have my $12000 returned (or part thereof) but again I was told it was working fine. I have tried them again but they are now out of business! Just this week I have tried another solar installer who has already told me there may not be anything we can do as it may cost more if we attempted to fix it, and to add extra panels will mean we lose our $0.25 rebate. Really not happy with our experience and can't seem to get a decent answer as to why it is operating as it is. I was never after a full reduction on my bill, but would have loved between 25% - 50% reduction.

  • John Robinson 7 years ago

    Life of the pannel 5 to 10 years , as the pannel gets older the less it will generate have we be conned again by the governments that where paying 20 to 30 cents for feeding into the grid ? The whole power industrie is a money make machine for the operators .

  • Sid Mitchell 7 years ago

    Can anybody tell me the current rebate for solar panel power and how long do you get this rebate for? Also I am looking at buying a house which is already set up with panels, is the rebate the previous owner transfered to me or do i have to renegotiate with the power companies? Cheers Sid

  • Stuart 7 years ago

    Wayne, why don't you get to use your own power? If you are net metered, that is exactly what you are doing, so everything you simultaneously produce and consume is worth 38c / kWh to you (you said that is your power rate). So, that's what solar does for you. The 6c is the wooden spoon prize for not consuming that power - it is not the goal. The goal is to use it. Najim, oversizing works fine. a 3000w system rarely produces 3000w, That is a potential size, not an average output. The inverter size is OK. Many system designs use this as common practice. No cause for alarm. Anna. your bill probably only shows export. Self consumption (which is the goal of solar) is 'lost' from an information point of view. You could look at kWh produced on the inverter, and then look at kWh you are paid for as export, and the difference is self consumption. You can value that at the rate you pay per kWh for power to work out the value it gave you. Forget the $20, that is only the exported amount. Kat, your 'sun hours' calc is misleading. Not all sunlight is equal. the kWh / kW ratio nis what matters (for example 3.9 kWh / kW as a rule of thumb in Sydney). This takes into account sun, and the power of that sun, and weather. The CEC guide has figures for each city.

  • Doug 7 years ago

    You must have enough panels to keep your invertor running at full output in reasonable sunshine, I have 6000 watts of panels feeding a 5000 watt invertor. I amalways making more than I use and receive credit during daylight hours so that over a year I am always in vront and do not have to pay for the power I use outside of daylight hours.

  • Najim 7 years ago

    Hello peter, I have below question. Recently I have installed 3kw system from energy Australia Panels are 12x250W jinko brand. Inverter is Fronious IG 30. I have checked its data sheet and found that , this inventer's maximum output delivering capacity is 2500W. I think the configuration Energy Australia sold me is not right. Panels are capable to deliver output upto 3000W, however my inverter can only invert upto 2500W. Should I ask Energy Australia to review my configuration and upgrade the inventer?

  • Vivian 7 years ago

    Vivek - do yourself a favor and ditch those halogens! you can get 50W equivalents from bunnings for about $35 for a pack of 4 - that only use 5w each. I got a 3kw solar installed for my mum in qld - and it generates about 10 on a cloudy wintery day and a little over 18 kwh on sunny summer days. you can expect an average of about 4 to 5.5 peak solar hours equivalent per day, so if you get a 1.5 kw system, it will generate about 1.5 x 5 = 7.5 kwh. But you will only get paid 8c a kw for power you feed into the grid. Since your halogens are burning 12x50w each, that's 600wh per hour - and you will be using that power when the electricity company is charging you peak rates of about 36c oer kwh - in other words, having your lights on for 3 hours at night will will burn through the credit you get if all your power was fed onto the grid during the day, if you get a 1.5kw system. replace them with LED lights. If you are using AC, it's a good idea to get a little more solar (say, 3kw if you have 2 kw of airconditioning) and use it to offset the running costs of the AC and fridge, as you are intending - esp. during the summer. Also heating with an airconditioner is 4x more efficient than using radiative heating like traditional bar heaters or electric oil heaters, because it is moving heat instead of creating it.

  • Don 7 years ago

    i put 22 panels on my roof it covers all our usage and pumps it back into the grid too i havent had a bill in 3 years and get heaps back once a year from our supplier i use my aircon as i always have my pool pump keeps my pool crystal clear ,,yep i thought ahead put my hand in my pocket and signed up for the 44c kwh woo hoo im not whingin all the folk whingin have tunnel vision i look at the big picture , anyway might go turn on my aircon in my room and waste some power ,,,have a nice day

  • Mauro Maitan 7 years ago

    I installed a solar system 2 years ago, and I disagree with some of the comments saying that (for instance), it knocks the occasional 20 dollars off the bills. Having the panels and saving is the combination of several factors, as below: - the amount of power you put back into the grid. This is the amount that will appear as a minus on your bill, that is, once the amount of power you have actually used will be deducted from it - during the day, most of the appliances you have running, will be running on the power generated by the panels. This might not be an evident saving, but it is. This is what will decrease your bills, as the power off your solar panels is virtually free (after your have paid them off) - find an energy provider who is solar friendly. I use Momentum in Melbourne. They work mainly with renewable energy sources, and when the rates go up, they only pass on the increase authorised by the government, no profiteering there. - Last, but not least, you also need to start saving inside the home: low consumption lights, energy efficient appliances, a bit of common sense like switching off lights that do not need to be on and switching off the powerpoints when you are not using appliances. All the above yielded us a saving of approximately AUD 400.00 per quarter, equating to about 1600 dollars per year. Panels paid off in two years, and then it is just savings. cheers

  • Gazwald 7 years ago

    Vivek, get rid of the 50W downlights and put in LED lights and turn the 600W draw into a 60W draw (rough estimate!) That will save you money straight away.

  • Wayne Flint 7 years ago

    Unless you can use your own power solar power is a myth. I have to use my power suppliers power first at an all up total cost of 0.38 cent per K/w and then I get a 0.06 (six) per K/w rebate for the power I make. I make enough power to run my entire home summer and most in winter but you can't use your own power. In short the NSW government solar rebate is a short term loan from the government which you pay back by generating cheap power for NSW To run subsidised water desalination plants and aluminium smelters. The Power suppliers than take your green power at .six cents and resell it as GREEN power for forty cents. Unless you can use your own power SOLAR is a CON. Wayne.

  • TJ 7 years ago

    Solar panels are far less effective in extreme heat and that pretty much means the entire summer in most parts of Australia. Maybe one of the experts here can share some figures about the drop in performance of various panels once they reach 50 degrees.

  • Gerwin 7 years ago

    Anna, a few years ago we installed 8 panels with an output of roughly 2 kwh. Our power bill immediately halved and the savings will make the investment cost effective in around 5 years. From then on it is profit. That is a pretty healthy return to and investment that also saves the environment. We plan to put more in but need greater roof space...

  • Chris Rees 7 years ago

    I came across this by chance, and am deeply impressed at Peter's comprehensive answer. I hope Anna takes up his suggestion and checks her system out, and Peter, it's great to see someone go to such lengths to explain what the problems might be purely because you have the knowledge and with nothing to gain from taking the time to do it. Good on you. Chris

  • Richard, Red Hill. 7 years ago

    Hello Kat and readers, This calculation is great, telling you how many panels are needed to generate the same kwatts of electricity as that used each day. But it doesn't seem to take into account time of day and power-company buy/sell rates? For a simple case, if I use say half my electricity during solar hours (day-time) and half during the night when I pay say 24c a kwh for it, while selling excess kwh during the day at 8c, (one third of 24c), then I will need more panels, I think? My calculation is that to generate 24c to pay for a night-time kwh, I need to generate 3 kwh during the day which I sell to the grid at 8c. So to cover the kwh consumed at night, assuming the same 2.8kw system in the example above, I would actually need (half) 1.4kw to generate daytime-use power plus 1.4kw times 3 (4.2kw) to generate enough kwh, to sell, to be able buy my night-time kwh. Therefore I need a 5.6kw system (28 panels!), double the 2.8kw system, assuming that I want to generate enough power to reduce my bills to zero. In the simple example, with half my power being bought from the power-company, a 2.8kw system should reduce my bills by 62%, still a good saving.

  • Noel Olive 7 years ago

    Anna, I advise you to take peters good advice,6years ago he supplied me with a solar Panel kit for my carav.an. 2 years ago his team fitted a solar system to our home,not one problem and plenty of power.We are very fortunate to have him in Coffs Harbour. regards Noel olive.

  • vivek 7 years ago

    I have 12 halogen downlights, 50W each, usually only turned on during the night time when we are at home. We work therefore we are usually not at home during the day. Only thing that consumes the power during the day are - Fridge, clock on the oven, clock on microwave and I think the water heater runs on the off peak meter. If I put solar panel on the roof the most consumption of the electricity generated will be for fridge, is it a lot to justify solar panels on the roof? Are the feed in tariff enough to justify the solar panels on the roof? Given that most of the power consumption is overnight, is it possible to store the energy, will the cost of batteries justifiable? if at all i get the solar I will leave the aircon running throughout the day, even when we are not at home.

  • Peter Bulanyi 7 years ago

    Anna, I'm sure there is more to your situation. These numbers are very rough, but this is what should occur with your system. 1. Assuming the panels are the smallest typically installed a few years ago at 200Watts each, that makes your system 2.4kW (2.4) 2. Assume conservatively available annual average Peak Sun Hours (PSH) at your location of 4 hours (4) 3. Assume a low Performance Ratio (PR) of 70% (0.7) 4. Assume electricty costs from your energy retailer are 30c/kWh (0.3) If the above conservative figures are assumed then the lowest bimonthly, 60 day (60) dollar generation should be (very roughly) this; 2.4 x 0.7 x 4 x 0.30 x 60 = 121 dollars ($121) Solar energy, clearly is seasonal, so the above average of $121 per 60 days will be higher in summer and lower in winter, but never ever only $20. i propose that perplexing puzzle of poor PV performance at your place is probably one of the following; 1. Your system is NET metered meaning the solar energy you consume in the house during the day, is never registered on your billing meter in the meter box. The dollar value is still there because if you self consumed the energy, you saved the cost had it otherwise been purchased from your supplier. Unfortunately there is no way to quantify the amount from the your bill, however your inverter may have a built in energy meter that can display how much solar energy is being produced and this provide the dollar return information to you. 2. The system is well installed but is seriously under performing. Things break. It is possible that the solar panels, inverter or wiring have an issue that is causing a major impact on production. The only way to know is to have a qualified and solar experienced technician review the systems performance and advise you accordingly. 3. The system was not installed well and has significant shade on the panels, is incorrectly wired, poorly designed, or configured. Again the only way is to have a trained technician review the installation and report to you. Anna, Clearly I am from the solar industry. I only chanced upon this blog, and your comment, but I can honestly say with hand on heart that since installing solar systems since 1989, I have never had a customer call back and ask me to remove their solar panels due to unsatisfactory energy yield. The technology is amazing, and should be fulfilling its promise of providing you with a return on your investment. Something isn't right with your system, or the tally of energy and dollar cost. Perhaps the time of use of energy at your place means that the bulk of your solar power is exported and you are indeed receiving no value fornthatbfrom the energy retailer. That can be also be rectified with some instructions on what to do. I'm sure you can solve the riddle by engaging a technician to investigate, report and advise on what isn't working for you with your solar power system. Regards, Peter Bulanyi.

  • Anna Mortimore 7 years ago

    A couple of years ago I had 12 panels installed on my roof. As I live in WA thought this would really put a dent in my power bills. However, it only takes $20 odd of my bimonthly account. At this rate, we will never pay for the panels in my lifetime! Sorry I did it now!

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