The 9 Solar Power Questions You Need to Answer First

If you live in the Southeastern US, you live in a prime solar power region. It has over 210 days of sun and over 260 days over 70oF per year. And with installation costs coming down while the technology continues to improve, the benefits for solar continue to mount.

But deciding to switch to solar is about more than sunlight and costs – as important factors as those are.

Here are 9 questions about solar power you need to ask about your home, farm, or business, and the factors to consider when answering them. For some of these questions, you’ll need a solar energy consultant or technician to help.

9 Solar Power Questions and Answers

1. Does temperature matter?

Yes, a little. Surprisingly, more heat actually reduces solar panel efficiency. While Georgia gets over 210 days of sun per year, 70 of those days are over 90oF. While the losses in efficiency aren’t that significant, they are a factor to consider. However, what matters more is the amount of sun that hits your structure at the right angle. So a really hot summer with lots of sun is still better than a mild summer (better solar temperatures) with more clouds.

This does mean that the best times of year for solar efficiency in Georgia and South Carolina are the spring and fall. See Georgia’s solar energy weather data here.

2.  Should humidity, hurricanes, or other weather patterns cause me to worry?

It depends on what kind of system you’re installing. For land-based systems, the weather is a big concern. For instance, if you live in a floodplain, your panels need to be tall enough to avoid getting covered by water in case of a flood. If hurricanes and high winds are expected, you’ll also need extra structural support. For roof-based systems this is a little less important. Learn more about how solar panels hold up in hurricanes here.

But humidity, especially near the ocean, will cause corrosion. There are special materials and coatings that will prevent this.

3. Does the type of solar panel matter? Are all panels basically the same?

They are not all the same. They can differ in several factors:

  • Size
  • Efficiency
  • Capacity

These three factors will affect the price and the amount of power your solar array can produce. Figuring out what’s best for you takes time and the help of a solar panel expert. But the remaining questions will help give you an idea of what they’ll be looking at.

But first, let’s be clear on our terms. Size is pretty obvious – how big is the panel, and how many can fit on your roof or other desired location.

Solar Efficiency: The percentage of sunlight that gets converted to actual solar energy. Typical efficiencies are small, from 10-15% or so.

Solar Capacity: The amount of actual power produced by a panel.

These terms are intertwined. For example – if two panels have the same capacity rating, they will produce the same amount of power regardless of size or efficiency. This is because a larger panel with lower efficiency can in theory produce the same power as a smaller panel with higher efficiency. You can learn more about these concepts from this solar company in India.

4.  What about shade? Do my trees or neighbors’ taller houses matter?

shadows on even small section of solar panel array weakens the total outputYes. This is actually the #1 issue to be concerned about. Shadows kill solar energy. While this may seem obvious, the full extent of it may not be. Solar panel arrays are all interlinked, and this causes them to function kind of like those Christmas tree lights where one dead bulb kills the whole string.

Shadows over just a portion of your solar panels will reduce or eliminate the power output of the whole array. So it’s more than just trees you have to worry about. See the photo at the right of a rogue roof vent sabotaging a solar array.

However, with power optimizers and microinverters, some of the energy losses from shade can be reduced.

The good news is, your solar consultant will be watching out for every source of shadow – at every season of the year. Huh? Every season?

Remember – the sun is in a different position in the sky in the winter compared to the summer. So the tree, the chimney, the vent on the roof, and the water tower in the distance will not cast their shadows in the same place all year. Yes, this can get complicated. That’s why you don’t go out and buy a bunch of solar panels and figure, “I can just install them myself. How hard can it be?” This isn’t a new toilet. No, you can’t do it yourself – not if you want them to produce the maximum amount of energy.

Also, let’s not forget: Trees grow. The main goal is unobstructed sunlight from 9am to 3pm from spring through fall. But the ideal goal is full sunlight all year round. Your solar energy consultant should be hyper-focused on any and all ‘shadow-casters’ on and around your location.

Bottom line – don’t plant any tall trees near your house if you’re thinking about installing solar panels.

5.  Which side of the roof is best for solar panels?

The south side, for northern hemisphere. East isn’t bad either, and west can work too. This assumes your roof isn’t flat, in which case this question doesn’t apply.

South is best because it receives the most direct sunlight for the longest portion of the day. But east captures the morning and advancing sunlight. And west captures the afternoon and setting sun. Tilted properly, panels facing these directions can still be quite effective. And if your roof is angled more like southeast, or southwest, then that will be somewhere in the middle.

6.  What do you mean tilted properly?

Direct normal irradiance isn’t 100% unless solar panels are angled to the right latitudeOh boy. Now it gets really complicated. When you really study solar energy, you start getting into astronomy, the magnetic field of the earth, and all kinds of wacky science stuff. We’re trying to keep it simple.

But remember, the Earth is titled, and it receives sunlight differently throughout the year because the angle of the sunlight changes. This is also affected by the latitude – the horizontal lines around the planet that mark how far from the equator a location is.

Georgia’s latitudes go from 31-35oN. This means, for solar panels to receive the most direct sunlight, they must be tilted to compensate for the latitude of the earth. So if your house is at a latitude of 33oN, then your south-facing panels should be angled at 33o. Again – your solar energy consultant will consider all this.

But if you remember question 4 – shade is the most critical factor of all. Latitudes and angles of tilt do matter, but not nearly as much as shade. For instance, suppose you live in Tampa and have perfectly titled south-facing solar panels receiving 100% direct sunlight.

How much efficiency is lost if the angle is not perfectly aligned? This table shows that it’s not a huge difference (this data is for Tampa, FL):

chart showing the angle of latitude vs. the percent of solar radiation received

And even if your house doesn’t face directly south, but sits at maybe a 45o angle and faces southeast and southwest, you’ll still receive over 90% solar radiation at up to 20o off the ideal latitude.

All this to say – angle of tilt matters, but not nearly as much as shade. You can also buy “solar trackers,” which are panels that adjust their angle throughout the day to maintain 100% solar radiation as long as possible, but these are more expensive.

The next 3 questions are about roofs. If you’re installing land-based solar panels, these questions won’t apply to you.

7.  I’m pretty sure I know the answer, but does size of roof matter?

Yes, you do know the answer – it matters. You can fit more panels on a larger roof. However this goes back to the efficiency/capacity relationship. If you have a smaller roof but want a certain power output from your solar array, you would opt for smaller panels with higher efficiency. If you’ve got a larger roof, you have more options.

How much area does it take? Well, we did science before, so here’s the math lesson for the day. Here’s an equation that tells you how much area you’ll need for a certain power output (this gives your answer in square meters, not square feet):

A = P/E.

A is the Area of roof you’ll need – this is what we want to know.

P is the desired Power output you want at peak capacity.

E is the Efficiency of your solar panels.

So if you want to produce 5 kWh of power, then P = 5

Suppose the panels you want are 14% efficient. So E = .14

Thus, the Area of roof you’ll need for your panels is 35.7 m2

The real area will be larger, because you can’t put panels side by side with no space between them. They might cast shade on each other, for one. And there are several other reasons. But you should expect to add around 10% to whatever Area this formula gives you. In our example, that would mean more like 40 square meters or so.

A meter is similar to a yard – not exact, but close. There are 3 feet in a yard. So 40 m2 is about 40 yd2, which means about 360 ft2. (8yd X 5yd = 24ft X 15ft)

You may not know yet how much power you want or need from your solar panel array. That’s okay. But your available space will determine whether you can completely wipe out your power bill, or reduce it by some percentage.

To calculate how much power you’ll need and money you’ll save, use this tutorial for the PVWatts solar calculator.

8.  Does the type of roof material make a difference?

It’s not a huge issue. Some roofs are more expensive than others, and some last longer. Asphalt shingles are the cheapest material, but they also have the shortest length of life. Tiles of various types, metal, gravel, and other materials have varying shelf lives.

Also, the type and thickness of the roof affects the installation process a bit. But that all gets taken care of by the installers.

9.  What if my roof is old? Should I replace it first?

Yes. If you intend to install solar panels – you will make life much easier for yourself (and save money) by replacing the roof first. If you install your solar panels first, then you’ll have to temporarily uninstall them to replace the rotting roof. That will cost more than replacing it now and installing the panels afterward.

And this is when the type of roof matters a bit more. Knowing in advance that asphalt shingles don’t last as long but are cheaper to install, you want to think about how your roof’s current health coincides with your solar energy plans.

The good news is, if you replace your roof as part of your solar installation, you can include those costs in your federal tax credit calculations. That means a new roof for 30% less than the actual cost. Learn more about solar tax credits here.

There’s no set answer here, and every situation is different. These are questions to ask your solar energy consultant once they can see your specific situation.

What’s Next?

If you know you want to install solar panels, contact Coastal Solar today and schedule a consultation with one of our experts.

If you’ve got more solar power questions, you can call or email us with those as well. Taking pictures of your home or roof and sending them with your email might help if you want to discuss your situation over the phone.

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2017-03-31T09:32:18+00:00