Solar technology has come a long way. The panels, batteries, and inverters of today are so good that solar is finally a practical and relatively affordable form of energy generation for home use.

That doesn’t mean you can just slap it all together and get your money’s worth, though. All this technology still needs a hand from us humans to ensure it works as well as it can. Some of the things you need to consider are so simple they are easy to overlook. In this article I want to talk about those things that affect how much energy you get from your solar power system and what you can do to minimize their effects.

solar roof

Light Sources and Type

Your solar panel can generate electricity from three main sources of light. The one everyone already knows is direct sunlight. This is light that leaves the surface of the sun, travels eight light minutes to reach the Earth, and then lands on your solar panel. Makes you feel special, right?

Solar panels can also generate some energy from “diffuse irradiation”. That is, light that has been scattered everywhere by clouds and other atmospheric interference. As well, anything that reflects light onto the panel will also add some energy into the mix.

Keep these three types of light in mind when you choose where to put your panels.


Solar panels have a specific operating range when it comes to heat. This will be listed in the specifications of the panel. If the panel gets too hot, then you’ll get less and less power out of the semiconductor as resistance builds. That’s a bit of a problem because solar panels are obviously in direct sunlight all day, at least if you’ve installed them properly. Since even the best panels are only about 25% efficient, you’re looking at a lot of waste heat cooking your panels.

So how can you make sure they don’t overheat? The best solution I have seen is to use ground-mounted panels, which have airflow beneath the panel which helps keep it cool. Roof-mounted panels bake on the hot roof itself, which lowers their efficiency. Mounting solutions that lift the panel away from the roof surface can also help with cooling.

New technologies such as bifacial panels may also help boost efficiency in high-heat circumstances.

Roof Direction

The rules around this are pretty straightforward. It’s best for the panels to face South, South East, or South West. Other directions can lead to losses of up to 15% when it comes to output. It’s not the end of the world, but if you want to get the most out of the panels that you paid for, then keep the roof direction in mind. Once again, this is something that can be solved by ground mounting your panels, but this comes with its own issues. Check my article on roof vs ground mounting for more info.

Panel Angle

Thanks to the way that light particles interact with the glass surface of the panel, as well as the movement of the sun over the course of the day, there is an optimal angle range for solar panel installations.

Panels should be between 30 and 60 degrees from the horizontal. What this means is that if your panel is flat on its back it’s not going to work well, except perhaps at exactly noon. Most angled roofs fall within this recommended range. If you have a flat roof, you should install your panels with angled roof brackets.

Solar Tracking

Following from the above, if you really want your panels to perform at their best all day and make as much power as possible, you need to hook them up with solar-tracking technology. This is basically a motorized mount that keeps the panel at an angle (and possibly direction) that makes the most power. This will get you closer to the theoretical power output figures written on the box.

Shadows and Shade

One of the biggest factors that makes your solar panels produce less juice is, well, something getting between it and the sun. Obviously, you won’t mount your panels behind something that blocks the sun, but the sun moves over the course of the day. This means that other buildings, trees, and tall objects in general may cast a shadow onto your roof at certain times of day. Before you buy panels and install them, check the proposed installation site to make sure it doesn’t have any shadow cast on it during the day.

Good Old Dirt and Dust

Just like everything else left outside, solar panels will eventually get covered in a layer of dust, dirt, leaves, bird droppings, and occasionally dead animals (don’t ask). This is going to put a big dent in your solar power generation, so make a point of getting up on the roof every few months and cleaning the surface of your panels. Of course, if you ground mount you won’t have to deal with the danger of doing this, but if you pay attention and observe proper safety then there should be no problem.

cleaning solar panels


Inclement weather is one of the biggest reasons that solar panels underperform. Anything that blocks direct sunlight is going to reduce the amount of power that you’ll get flowing into your system. There isn’t much we can do about the weather itself, but we can plan for it so that even with bad weather you’ll still get enough power.

Where you live in the world and what the typical patterns are can inform this issue. You may want to search for a solar insolation or irradiation map for your part of the world. See how many days of sunlight you will typically get. How many cloudy days are there on average? You want to estimate what the average efficiency is going to be during the year and during those periods where the weather tends to be terrible. Your choices are to add more battery capacity, add more panels for bad days, or live somewhere else.

Just keep in mind that even if you live in a cold part of the world, that doesn’t mean you can’t have solar power. What matters is how much sunshine you get, not how hot things are. In some circumstances, lower temperatures help panels do a better job of converting the sunshine that is available. It can actually be a decent trade off, although you still need to clean the snow off the panels!

Seasonal Solar Shift

When you first install your solar panels and calibrate them, you’ll see great power output, but drops are inevitable as the seasons change. This is because the apparent path of the sun across the sky shifts over the course of the year. Most solar tracking systems work for daily tracking, but not for annual shifts, so you’ll have to manually adjust your panels to take account of this. Automated systems are possible, but are only practical for pole-mounted ground installations with 2-axis tracking. Luckily you only have to make a few adjustments a year, since this shift is very slow.

Being Realistic About Performance

Let’s be real – you’ll never match the theoretical peak performance of your solar panels. All solar panels are rated under identical “ideal” conditions. While at some point in the day they may reach that same state briefly, it’s basically impossible to average at the peak.

The measures we looked at here are an attempt to get as close to peak performance as possible. However, there is a point of diminishing returns. Some optimizations are too much trouble or too much money for the gain you get. The final decision is yours, as always, but you should consult with a professional to get an idea of the cost and complexity of the various performance tweaks.

Perfect is the enemy of good, and the best that fans of solar power can hope for is “as good as it gets”. Maybe some disruptive technology will double our efficiencies over the next few years, but realistically we’ll have to be happy with getting enough power from the sun to actually free us from the grid.