South vs North Facing Solar Panels – Does It Matter?
Yes, yes it does matter if your panels are on a north or a south facing roof.
In fact, we wouldn’t install on a north facing roof unless there was some exceptional circumstances.
But why is the south facing roof better than the north?
Read on …
First, what is Solar Insolation?
Solar insolation is the power we can get from the sun at any given point … sometimes it’s also called Global Photovoltaic Power.
But you don’t have to start getting the slide rule and calculator out to get exact numbers to work out the exact amount of power your panels are going to generate.
Insolation changes from day-today, hour to hour, so it’s best just to work on averages.
The UK has an annual insolation of between 750 – 1,100 kilowatt-hours per square metre.
That is a lot of power!
That’s why, even with an efficiency of 22%, solar panels generate a huge amount of energy.
The reason we mention insolation is because that’s the amount of power the sun will give us if we position the panels in the perfect position to collect it.
Mounting Solar Panels: North, West, East or South
So, how do we position our panels to soak up as much of that power as we possibly can?
The sun rises in the east and sets in the west, that much we know from just looking up occasionally.
But, then we must consider the fact we are in the northern hemisphere and how far away from the equator we are.
Because we are in the northern hemisphere that means, if we look south we can see the sun all day because of the angle it hits the earth.
If we can see the sun all day, so can your panels.
Solar Panel angle is important too
The further south you go from the UK the warmer the weather gets, right?
Well, that’s because of the angle the sun hits the earth at.
The equator is in the middle of the planet and this is the nearest point you get to the sun – so obviously, that’s where the sun’s rays are at their most intense.
As you move north the light has to travel further and that means it cools down, or gets less intense.
So, what does that mean for your panels? It means they need to be at the correct angle to soak up all those lovely photons.
traditional and modern houses in the U , generally, have roofs angled between 30° and 40° - so we are on to a winner there!
The efficiency of the panels will decrease the further from the best angle and direction you get – a 35-degree pitch is perfect and, if the house is pointing due south too, you’re panels will function at the top of their efficiency rating.
What if you don’t have a south facing roof?
Not a problem!
While the south facing roof will soak up energy from dusk until dawn, you can farm the sun using other methods too.
An east west split is very popular in the world of domestic solar.
This method means you are harvesting the energy all day too – with one side of the house covering the morni8ng, and the other side looks after the afternoon sun.
One of the advantages of this kind of system is things get started a little earlier in the day.
Solar inverters have what is known as a ‘start up’ voltage, this is the minimum amount of energy need to kick a string of panels into action.
So, the panels on the east side of the house will start generating power slightly before panels fitted on a south facing roof.
In fact, southeast or southwest facing panels will get 80% of the daylight south facing panels do.
How to work out the best angle for your solar panels.
If you’re looking for the perfect angle it changes from season to season.
In winter, add 15 degrees to your latitude, in summer take 15 degrees away.
For instance, London is at 51 degrees latitude – so panels should be at 34 degrees and in winter that would be 66 degrees.
Of course, you’d have to be willing to spend a pretty penny if wanted your panels to take those angles, and the juice would not be worth the squeeze.
That’s why we stick to an average to keep the panels at the best they can be all year.
Can you install solar panels on a north-facing roof?
If you like, but we wouldn’t recommend it.
As we mentioned before, the startup voltage needed may not get reached in winter, which means you have panels on your roof that don’t work at all for 3 months of the year.
However, they will produce power for the rest of the year.
And, if your roof is northwest/east facing you’ll generate a good amount of electricity.
Can you put solar panels on a wall?
Technically, yes.
In fact, you can mount panels anywhere you like so long as you have the space ... and planning permission, of course.,
However, mounting on walls can present several problems.
On the average UK home, the walls will get more shading than the roof – other buildings, street future, trees, you name it they are all casting shadows on your walls.
Plus, if the panels themselves stick out from the wall by more than 20 cm you are going to have seek planning permission.
Mounting panels on a flat roof
Now, mounting panel on a flat roof is a doddle!
What’s more, you can point them in any direction you like.
When mounted on a flat roof, panels can be secured using a frame or you can put them on their own individual bins of boxes.
These are specially made for the purpose and will be angled tat between 30 and 40 degrees to make sure they get as much, strong daylight as possible.
The only disadvantage of flat roofs are; some are not load-bearing, so may not be safe, and they could suffer from a lot of shading if they are single storey.
Bad angles for your solar panels
There aren’t any angles that would render your panels ineffective, unless you pointed them at the floor of course.
Full efficiency is gained by facing the panels south and making sure they are angled between 30 to 40 degrees.
The further away from that positioning you get, the less efficient your panels will be – but any responsible installer will take that into account and design your system to work for your home.
