Why North Roof rules in solar?

why-north-for-solar

Reasons North roof is the best for solar

There are more than 1.5 million homes in Australia with rooftop solar. I don’t have statistics on all roofs, but I can tell you one thing – a large portion of them with solar panels are likely facing North or close to North.

You may not have planned, but if you happen to have large open roof space that faces North, good for you.

North facing roof is considered the best option for solar electric system installations. In this post, I will give you three reasons why you should feel good about your North roof if you are planning for solar for you home. 

For others, if you have a flat roof (uncommon for residential home but very common if commercial building), solar panels will be inclined facing North. Again, you want to know why, right?

Without further delay, here are three reasons why North roof is unsurpassable…

Reason#1:

North roof receives more sunlight in a day; it is also spread wider through the day.

roof-solar-outputroof-solar-output

To prove this point, let’s look for a moment on other roof orientations, one by one.

EAST ROOF:

East roof is great, but only in the morning hours. What happens rest of the day? Well, it varies.

If it’s summer, east-facing panels will receive decent amount of sunlight even in the late afternoon hours- although not as high as on the north roof.

In winter, except for first few morning hours, east-facing panels will not receive enough sunlight rest of the day to generate meaningful solar electricity to power your home. Thus, you will be relying on grid power for most of the day.

The first diagram at the top of this post shows that annual solar irradiance from east roof is 11% less than north. So, clearly, North prevails East.

If you have East Roof and want to read more about strictly East facing roof’s solar potential, I have written a separate post here: East Roof orientation.

WEST ROOF:

West roof is better than North for late afternoon and evening hours. Solar panels on west-facing roof can take advantage of sunlight on the west side before the sunset.

Again, in the summer, west-facing solar panels will generate solar electricity most of the day, which is great. During this time of the year, the sun is higher in the sky. Which means the sunlight strikes west roof sooner in the morning and longer through the evening, than it would in the winter.

Just like east roof, solar power production in winter from west roof lasts only couple of hours in the evening. Rest of the day, there is not enough sunlight striking the panels to generate power. Consequently, you’ll be relying on grid power for earlier part of the day.

Annual solar irradiance on west roof falls short of north by 15%.

Do you have West roof and wondering if solar is worth? Here is a link to a detail analysis of strictly West facing that I wrote before: West Roof orientation

SOUTH ROOF:

Now, the most dreaded roof orientation in Australia when it comes to solar – the south roof.

The reason is obvious because south is the other side of north. And, the opposite of “best” is “worst”.

That was a silly explanation.

A more scientific explanation has to do with the sun path, which brings me to my second reason.

Do you want to know more about strictly South roof? Look up my previous post about South roof- How bad is it?.

Reason#2:

Sun path favors north roof in winter.

east-north-solar-generation

If you don’t know what sun path means, what I am referring to here is the path sun takes while moving east to west. Sun takes different path from east to west all year round.

Here is a little somewhat embarrasing story from my life.

Once, I used to live in a very cold place (somewhere in northern hemisphere). The front of my house faced north. This is equivalent of south in Australia for solar radiation. Just remember this in my story below..

In the winter, when it snowed heavily leaving piles of snow around the house, I had to shovel the snow out on my own, especially on the driveway.

It frustrated me that my neighbor’s front yard somehow managed to melt the snow away. But mine didn’t. When I returned from work, I saw the same piles of snow when I left in my driveway while my neighbor’s, across the street from me, was clean. At the time I thought my neighbor was really good at cleaning the snow from the driveway.

What I didn’t realize was that their front of the house was facing south (same as north in Australia). And that made all the difference.

In peak winter, sun path is the shortest and tilted far north in Australia. Sun rises in the northeast corner and sets in the northwest corner. It moves east to west tilted north. Because the sun is so low, south roof is deprived of sunlight for much of the winter.

For the same reason, except for the morning and the evening, East and West roof also do not receive much sunlight rest of the day.

If you look at the chart above for East roof, it is clear that the production gap widens significantly in the winter. Same is true for West roof as well.

[My front yard sat there without any direct sunlight, and in the shadow of my house most of the day. That was the reason why the snow didn’t melt. I understood this much later and felt pretty dumb not knowing in the first place. Oh, well.]

Reason #3:

Households have the potential to save more

North roof is the best for solar because it receives more sunlight, which means more solar electricity production, which means less import of grid electricity, which means more *potential* of savings on your power bill. It is as simple as that. 

But here is the catch: you should be able to self consume the solar electricity while it is being produced. Only by doing so, you will import less from the grid and reduce your electricity bill. Hence, the use of *potential*.

There you go. Three serious reasons why North roof is the greatest of all for solar panels. If you have been considering solar and have north roof, your investment is sure to payoff sooner, as long as you consume the solar power that is generated..

And you are dead serious about purchasing a system, before you pick your solar company, make sure to get several quotes (at least three)..

Lastly,

Is the prospect of solar all dark and gloomy if you don’t have an open roof space facing north? How much of a disadvantage is East, West or South roof compared to north roof?

I know that not everyone has a roof that faces North. Which is why I have written separate blog posts analyzing East, West and South roof individually. You can read them at your convenience. Below are the links.

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