January 23, 2024

When a Solar Engineer Designs their Home's Solar PV System

What happens when a solar engineer gets the chance to put solar panels on their own house? Rana Mitra did just that and shows how he gained an additional 6% from modifying the position of the previously proposed solar array.


Hi all, Rana here – I’m an electrical engineer and CEC accredited solar & remote area power system designer.

I've worked in the solar industry for the past 15 years, the most recent 7 of I have been leading the hybrid/remote area power system design department at Enhar.

During these years I've worked on hundreds of solar projects; consulting on solar feasibility, design and installation, car park solar projects, remote area power systems & battery projects including commercial solar roll outs for Melbourne University.

Last September my partner and I bought our first house. It was new build where the vendors had organised a solar installation that was pending through their builders.  I have always wanted to design a ‘you beaut’ solar PV system for my own home and was keenly aware of all the shortcomings that are all too prevalent in budget solar installations.

We were not about to live with a sub-standard system!  

The day after we first inspected the house and decided it was a good fit for us, I was hot on the emails to the real estate agent – offering to review and assist with the solar install.  

One month later we won the house at auction and signed the contract. I was then able to get some details and begin liaising with the solar company the builders had lined up. 

Reviewing the initial system design

As expected, the solar installation company chosen appeared to be a low-cost volume solar retailer with budget components chosen for the system. It also did not appear that they had put much thought into the design of the system.

I had numerous concerns with letting a relatively low-cost/volume solar retailer, whose costs appeared to be less than the wholesale prices of the components to install solar panels on our roof. These included: concerns about the quality of the installation, the longevity/waterproofing of penetrations, aesthetics/integrity of wiring runs and with getting the wind loading structural engineering work done right to ensure the mounting system would be compliant with standards.

The proposed design used low-cost components and a budget racking system that appeared to not have the necessary documentation required to ensure that the structural compliance requirements would be assured.

The solar retailer’s design consisted of only West facing panels, which would not provide power generation in the mornings.  We started off by asking them to improve their design to include both East and West facing panels to the South of the roof area and agreeing to pay them to use premium components.  

After extensive correspondence we learned that the vendors could be refunded their deposit as the house was going to be transferred to our names, we hit the jackpot!

I was now free to design the entire system and choose my own installers. I proceeded to get 3 quotes from installers I knew and start to price up all the components.  

A bird's eye view of a buildingDescription automatically generated
Fig 1: Solar retailer design – all West facing panels with a large tree to the NE.  No morning generation and shade loss in the afternoon.

Developing my design

Under my proposed design both the East and West facing roof areas would have panels so that the solar array would be subject to less shading and generate power for a larger section of the day. Paired with a Fronius inverter that had a superior MPPT curve scanning functionality, this would help ensure our energy yields would be maximised during the colder months despite the increased shading from the large tree to the North.

The below images show the shade coverage of the initial design (top) and my design (bottom) and their shade coverage at 11:45am March Equinox.

Fig 2: Solar Retail Design Shade model (11:45am March Equinox)
A pencil drawing a house
Fig 3: Shade model of my design (11:45am March Equinox)

We also wanted a Fronius smart meter which lets us see our consumption vs. generation in almost real time. This data has helped us to start to run our higher loads (heat pump hot water, clothes and dish washing etc.) during periods of sufficient solar generation.

Our New Years Day profile looked like this!  

Fig 4: New Year’s Day loads vs. generation (yes it was sunny that day)

Selection of components

While selecting components, I had a few criteria in mind to ensure that the systems will safe and efficient well into the future.

  1. Reliability/heat tolerance: as temperatures get more extreme under climate change, I wanted to ensure that our inverter system would not derate in hot conditions when we would be more likely to need air conditioning.  The active cooling and heat sinks on the Gen 24 inverters ensure that this is the case as well as helping ensure the longevity of the electronic components inside.
  2. Arc fault protection: the Fronius inverters have been shown to be able to prevent arc faults in solar DC which helps to prevent potential fires resulting from solar installations.  
  3. PV power point functionality: having a power supply available to charge/run radio and communications equipment during emergencies and power outages was important.

We ended up going for the REC Solar 405TP5 solar modules which made in Singapore but without a super-premium price point.  The clamping zones on these modules were also much better suited to our roof’s screw line spacing allowing us to use a conventional rail based solar mounting frame system. 

We also looked at mainstream Chinese solar modules and while they ~20-70% cheaper than the alternatives, their ethics are under scrutiny due to the major humanitarian concerns associated with the ubiquitous Chinese solar module manufacturers.

Preparing the roof and installation

I discovered a potential project ending issue after I managed to get on the roof. It turns out that the roof is made from Lysaght Hi-10, 450 Gal sheet and while galvanised steel roofs are increasingly rare, they can be subject to increased corrosion due to the inert run-off effect from aluminium framed solar panels. 

As consultants we do not recommend solar on gal sheet roof, however in this instance, as the roof isn’t very visible - I wasn’t going to not have solar! For peace of mind I applied some rust shield enamel paint to some of the spaces between the modules and will be carefully monitoring the roof for corrosion and applying rust remover – painting over sections as required. 

The Clenergy Mounting frame engineering team were incredibly helpful with this project, giving us a site-specific engineering certificate for the design that lets us have the modules less 200mm to the roof ridge line (which I needed to help reduce shade losses form the neighbouring roof to the West).  They were also super responsive and helpful with my many questions and concerns.  

The Enhar electrician team led by Greg and David Kincaid ended up installing this system and left some space between array sections so I would be able to access the roof areas from a harness point.

Dream solar system achieved!

I couldn’t be happier with the result, especially since this allowed me to be involved in the installation process (if mainly only for catering purposes) and knowing that we had an experienced and excellent installation team where I could be sure that the penetrations/clamps torque etc. would be right on the ball!

Massive thanks to Enhar for helping me get the dream solar installation I always wanted and hopefully this was an interesting article and helpful for people looking at solar for their own roof.

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