Ch 7. Is my house right for solar?

Quick Summary:

  • Do you own your own roof space?
  • Does part of your roof face north, west or east in the Southern Hemisphere, or south, west or east in the Northern Hemisphere? And is that roof space unshaded for the majority of the day, for most of the year?
  • Is there enough unshaded area to fit 8 or more solar panels? (Approx 12 sq. meters, or 130 sq. feet)

If yes to all of the above, you can probably install a productive solar system on your house. However, there are a few other factors that may influence the viability, or cost of install. We should also take a closer look at some of those questions.

1. Direction of roof

In the southern hemisphere, a north facing roof is optimal for solar production throughout the entire day (south facing in the northern hemisphere). Depending on the pitch of the roof, a west or east facing roof will decrease your solar output across the day by about 15% compared to the optimal. Having solar on an east or west facing roof is not ideal if you are home all day to use your solar power, or if you receive a nice feed-in tariff (or net metering, see next chapter for more on that). However, it’s also not a deal breaker if you only have an east or west facing roof, because 15% is not a massive amount, plus solar panels are pretty cheap these days so you can always oversize the inverter (put up greater kW of panels than the inverter size) in order to go some way to counter the loss from the roof direction.

Furthermore, if you do not get paid much for the solar that you export, and you aren’t home throughout the day, then you may in fact prefer to have solar installed on your east or west facing roof. That is because the sun rises in the east and sets in the west (in both hemispheres), which means an east facing solar system will produce more power in the morning and a west facing system will produce more in the evening. Therefore if you use most of your power in the morning and evening, you will consume more of your own solar power if you have an east and/or west facing install.

2. Shading

There is a lot that can be said about shading, however the most important thing you need to know is that your solar panels will not generate power when they are shaded. If you have big beautiful trees surrounding your house that provide lots of shade in summer, then buying a solar system would likely be a waste of money.

The calculations are too complex to go into here as to whether or not the shade on your house is a deal breaker or not. It is suffice to say that if you get a decent amount of sun on some of your roof for most of the year, then it is worth getting an assessment from a solar provider. Any decent solar company should be able to give you an accurate idea of how much energy your system will produce, and how much it will be affected by shade. If you really want to find this out for yourself, there are plenty of online apps and tools which you can use.

3. Type of roof

Installers can install a solar system on most types of roof material, however there are some roofs that are unsuitable. Slate for example can prove difficult, and fibreglass generally not possible.

The pitch of your roof can also lead to extra cost of installation. If you have a steep roof, it can be dangerous to install on, which means the installers may need special access and safety equipment (this can add hundreds of dollars). Likewise if the roof is difficult to access, the installers may need special access equipment. If the roof is flat, or nearly flat, you will likely require extra racking in order to face the panels to the direction of the sun.


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