Factors affecting solar system production

Shading

Shading has a large effect on the performance of a solar power system. Outside the hours of 9am-3pm you can get away with some shading however shading within these hours can have a drastic affect to your solar production and energy savings.

Even partial shading of the system can have a large effect as all panels in a section need to run at the same voltage. If one panel is shaded even partially, this will bring down the production of the whole system. There are ways around this such as splitting the array into multiple strings or using micro inverters on the back of panels.

Always ask your installer when being quoted what effect shading will have and what your options are to combat any shading.

Roof Orientation

In the southern hemisphere (Australia), north facing roofs are the best for solar. If your roof isn’t north facing, that’s okay, the loss from facing the system east or west won’t matter too much and you can have your panels placed to suit your high energy usage times.

Roof Orientation Production Loss
North no losses
North East/North West 7% loss
East/West 12% loss
South 28% loss

 

Direction Time of Day
North Receives the most sunlight throughout the day
East Generates more energy in the morning and less in the afternoon
West Generates more energy in the afternoon and less in the morning
South Avoid when possible

Roof Inclination

To get the best production from your panels, your roof should be pitched at the same degrees as the latitude of your location.

For example, Brisbane’s coordinates are as follows – Latitude 27°25’SLongitude 153° 9′ E.
This means that the best roof pitch is 27 degrees which is about what most roofs are.

If your pitch is different to this, don’t worry, for every 5 degrees difference from this, you lose 1% production. So if the panels were laid flat, you’d only lose about 5% production.

It’s recommend you have at least have about 5 degree tilt so that water can run off and the panel can self clean.

Tilting panels

Should you use tilt frames to tilt your panels so that they’re closer to the optimal angle? In 95% of cases, we would suggest using the extra money on more panels than tilt frames. This is because as mentioned before the difference in production for a 25 degree roof and a 0 degree roof is only 5%. Tilt frames may also have the following drawbacks:

  • They can catch the wind and can act as a sail putting greater stress on your roof structure.
  • Any increased production is offset by needing to leave spaces between rows of panels so that panels don’t cast shadows over each other.
  • Increased cost for the frames plus increased labour costs.

Summer vs Winter Production

Solar systems will always produce more energy in summer than in winter and this is due to the sun being higher in the sky and the days being longer. One interesting point which most people don’t realise is that solar systems don’t like too much heat and will produce around 20% less energy than their peak on a 40-degree day. Therefore, you may find that your solar system hits its peak production at any one point in time during spring or autumn. Overall though, your system will produce more units of energy during the summer months due to the longer days.

The temperature co-efficient is a guide for how much your panels dislike the heat and also an indicator of quality. This number tells you how much your panels will lose in production for every 1 degree over 25 degrees of surface temperature. The lower this number, the better.

Avg Daily Production = 1kW
(production from table below)
x System Size x 1
– percentage loss from shading
– percentage loss from inclination
– percentage loss from roof direction

 

See the guide below and then take into account the factors below, which will reduce the systems production.

 

Average daily production

City 1.0kW system 1.5kW system 2.0kW system 3.0kW system 4.0kW system
Adelaide 4.2kWh 6.3kWh 8.4kWh 12.6kWh 16.8kWh
Alice Springs 5.0kWh 7.5kWh 10.0kWh 15.0kWh 20.0kWh
Brisbane 4.2kWh 6.3kWh 8.4kWh 12.6kWh 16.8kWh
Cairns 4.2kWh 6.3kWh 8.4kWh 12.6kWh 16.8kWh
Canberra 4.3kWh 6.45kWh 8.6kWh 12.9kWh 17.2kWh
Darwin 4.4kWh 6.6kWh 8.8kWh 13.2kWh 17.6kWh
Hobart 3.5kWh 5.25kWh 7.0kWh 10.5kWh 14.0kWh
Melbourne 3.6kWh 5.4kWh 7.2kWh 10.8kWh 14.4kWh
Perth 4.4 kWh 6.6 kWh 8.8 kWh 13.2 kWh 17.6 kWh
Sydney 3.9 kWh 5.85 kWh 7.8 kWh 11.7 kWh 15.6 kWh
Data Source: PV-GC spreadsheet based on the CEC GC Design Guideline
The Rated output is that achieved in perfect laboratory conditions. The CEC design summary software takes these deratings into
 

Where in your solar journey are you?

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Understanding Batteries

Off-Grid Systems

For some households a battery system can be of great benefit and minimise a home’s reliance on the grid. However, it’s important to understand for a battery to be useful your solar system needs to be generating excess energy for the battery to store, which you can then use at night or when the sun is not out.

When selecting a battery, you’ll want to invest in a system that is most suited to your home and can drive the best return on investment (ROI). Despite a larger upfront cost, a higher quality battery may significantly increase your ROI.

    Battery systems start from $6,000 and costs can vary greatly based on the following factors:

  1. Cycle Life-Time

    The number of times a battery can fully charge and discharge.

  2. Battery Power (kW)

    How fast it can be charged or discharged.

  3. Storage Capacity (kWh)

    The maximum amount of energy a battery system can store.

  4. Battery Management System (BMS)

    An electronic ‘smart’ system that gathers data and manages the battery ensuring it does not overload or operate outside of its safe functioning zone..

  5. Inverter

    Battery systems require their own inverter if your solar system does not have a hybrid inverter.

  6. 'All-In-One Unit’

    A system which includes the battery, BMS and an inverter all in one unit.

  7. Warranty

    Length of time or cycles the battery system is under guarantee.

  8. Blackout Protection/Backup

    It’s important to note this is not a common feature of a battery system and could cost thousands of dollars to include. Blackout protection not only requires additional components but also a specialised installation and rewiring. For grid-connected homes, the cost for blackout protection can outweigh the benefit.

Additionally, if your purpose for adding battery is to go Off-Grid and become completely independent from the grid you will need to ensure your solar system can generate enough energy to power your home and your battery system is large enough to store this energy. For homes in metro areas going Off-grid is not cost effective and is only recommended for those in remote areas with limited access to the grid. Off-grid solar systems with battery start at approximately $30,000.