How Many Solar Panels Should You Buy

 How Many Solar Panels Should You Buy

The answer is simple if you have a reasonable electricity consumption and feeding tariff I recommend getting as many panels as are allowed by your local electricity network as many as you can afford and as many as will fit on your roof now scout's honor. The way the solar rebate works is paid per panel and it covers all or most of the cost of each panel from the wholesaler that means once the guys are on your roof. It actually costs very little to add more panels and the more panels you have the more energy.

You'll have to power your home especially in the morning late afternoon in winter and on overcast days here's an example of well-meaning put bad solar sizing advice.

Let's say a solar sales person works out that between nine in morning and five evening. When the sun shines you typically use eight kilowatt-hours of energy.

A three kilowatt solar system will generate about 12 kilowatt hours a day on average. So he tells you you're wasting your money getting any more panels.

12 kilowatt hours is way more than your 8 kilowatt hour’s usage. This advice is bad because averaging everything out will give you mediocre results and your bills will be higher than they need to be the three kilowatt solar system might cost four and a half grand for an extra fifteen hundred dollars you could get six point six kilowatts. Its look how much extra energy you'll get to use in the peak morning and evening times and how much extra energy you'll get in winter when you need the energy for heating.

That by small advice is starting to look like really crap advice and you may find this hard to believe that your next car is likely to be electric. If not your next one the one after that will almost certainly be electric when you start charging a car at home. You will be really grateful for those extra panels and although they're expensive at the moment home batteries will soon be commonplace to charge a battery through the year.

More panels are very useful. So you should get a big system.

Now let's understand what will limit how many panels. You can have what your local electricity network or distributed network. Service provider allows you to install your budget and the size of your roof let's go into.

A bit more detail on each of these. First limit on solar size your local network rules your dnsp is the entity that owns and maintains your local electricity network your electricity supply will either be

Single phase

Where one live wire is going from the grid to your home.

Two phase

Where there are two live wires.

Three phase

Where there are three live wires.

 Single phase homes are the most common.

This example is shows the limits each dnsp has for solar panel allowed.

A maximum of 5 kilowatts of inverter capacity per phase but the installation rules allow for 33% more panels than your rated inverter capacity.

33% more than 5 kilowatts is 6.6 kilowatts that's why you see so many ads advertising 6.6 kilowatts. You might have noticed some dnsp's allow you to have up to 10 kilowatts of inverter capacity on a single phase with a caveat that you're only allowed to export five kilowatts. That means you could theoretically have a 10 kilowatt inverter.

A huge 13.3 kilowatt system on your roof and export limit the whole system to five kilowatts meaning, you can only export five kilowatts of the grid at any given time that might sound nuts but it can make sense if you have big loads like pool heaters big air conditioners or even an electric car. Because the more you use in our home the less you've got available to export.

Imagine you have 13 kilowatts of panels with a 10 kilowatt inverter. You'll never generate more than 10 kilowatts. That's the inverters limit. And you'll never export more than 5 kilowatts the export limit.

But in the morning you'll get to 10 kilowatts much quicker giving you more energy sooner and in the evening your energy will drop off. Later you'll get a squarer curve and if you have big loads in your home your export limit can have little impact.

For example you have an electric car that pulls seven kilowatts when it's charging and it can charge for up to ten hours a day. I have a battery that charges at three kilowatts. I want lots of power for as long as possible

having said that export limiting does affect your solar savings and payback. So get your solar installer to run the numbers for you based on what you need to power now and in the future.

The second limit on solar size is your budget. This is pretty straightforward you can't put solar on if you can't pay for it.

You can also expect to pay more if your roof is difficult to install on or if you need electrical work done such as a switchboard upgrade.

What you'll notice is that for example

6.6 kilowatt solar systems are only marginally more expensive than five kilowatt systems.

Such oversized systems represent great bang for buck. Because as already mentioned the solar rebate is actually based on the number of panels. You have not your inverter capacity. The third limit to solar size is your roof space. It used to be the case that if you had limited roof space and needed to squeeze as much as possible.

Your only option was to pay through the nose for super high efficiency Rolls-Royce panel brands. Like LG. 

The sun power which make residential size panels up to 400 watts in size but nowadays many budget end panel manufacturers are making very efficient.

370 watt residential panels meaning if you're on a budget with limited roof space you can still squeeze a lot of solar generation out of your roof without top of the range panels to give you an idea of how much space a

6.6 kilowatt.

If you need to know more about solar panels then see my previous blog which I thoroughly covered

• ·         what to know about solar panels
• ·         what to ask when buying solar panels