Measuring the Efficiency of Solar Panels
Solar energy systems have the added benefits of very high efficiency, durability, and service life – they’re engineered for sustainability. This means fewer replacements and repairs, saving even more energy and precious resources.
A solar panel’s efficiency is measured by the percentage of power the panel converts absorbed sunlight to electricity. Because panels vary in size, the power produced is measured against the size of the panel. For this reason, it’s better to have a smaller panel that produces more energy. It is better to have a 2.5’ x 5’ panel that produces 4.5 kilowatt hours (kW) than a 3’ x 6’ panel that produces the same amount.
Sadly, not all solar panels are created equal. The highest quality panel operates at 42% efficiency. There are panels that produce energy at far lower efficiency rates—most of which are purchased through retail. This is why we don’t recommend building your own system.
Generally speaking, the more you invest up front on a solar panel system, the greater your return will be year after year. Overtime, the higher efficiency panels perform better, giving you a better bang for your buck.
Solar Photovoltaic vs. Solar Thermal
One of the most asked questions we get is whether a person should get solar photovoltaic panels or solar thermal panels. While the answer to that question lies in how much direct sunlight a roof gets, how big a roof is, and other factors, we thought it’d be helpful to first understand the differences between the two types of solar panel systems.
Solar Photovoltaic
Also called solar electric, photovoltaics are primarily used to provide energy to your home. They consist of an array of photovoltaic cells, made of silicon, that capture sunlight and convert it into energy. These systems integrate with your electric company’s power grid, off-setting the amount of energy you receive from the power company. Solar electric systems allow you to receive the financial benefits of both SRECs and Net Metering.
Solar Thermal
Solar Thermal systems, also called solar water heating systems, collect the sun’s energy and use it to heat the water in your house. The panels contain tubes filled with glycol, a non-toxic liquid similar to anti-freeze. Solar thermal panels trap the sun’s heat, which heats the glycol. Then, the glycol is moved through the tubes to a heat transfer system that heats your water. Depending on the size of the system, you can heat the water you use for bathing and washing. Or, if your home is heated with water radiant heat and can support a larger system, you could heat your entire house! Either way, you’ll save a lot of money on your electricity bill.
How to choose the right system
There are many factors that go into choosing which type of solar panel system to install. Here are a few questions that we typically ask when we do a solar analysis:
- Do you want to reduce or eliminate your electric bill?
- Are you concerned about future energy costs?
- Do you want to have a positive impact on the environment?
- Are you concerned about the appearance of a solar panel system?
- How much space do you have?
- Do you want to improve the resale value of your home?
- How much are you currently paying for electricity?
Four Reasons Why Building Your Own Solar Panels Is a BAD Idea
If you Google solar panels, most of the top results are for websites selling DIY solar panel kits. The same search on YouTube is filled with videos on making your own solar panels.
While building and installing your own solar panels might seem like a good way to save some money, there are several reasons why doing it yourself is a bad—sometimes even dangerous—idea. Here are five reasons why you should work with a professional solar panel installer:
1) You will pay more for materials.
Professional solar panel installers are able to obtain a higher quality product at a lower price. The panels you get at Home Depot or other online retailers are, to say the least, a much lower quality. They are less efficient and will generate less electricity, meaning that you will have to install more panels to generate the same amount of energy, which will ultimately cost you more than a high-quality solar panel you get from a professional company.
2) Doing your own electrical can be dangerous.
This might seem obvious to some, but you’d be surprised how many people think that can do their own electrical work without having any formal training. Unless you are an electrician, installing your own electrical devices, much less a set of solar panels, can be incredibly dangerous. A professional installer will have both roofing and electrical experience, and will know how to safely install your solar panels.
3) Protecting your purchase through the warranty
Companies can be picky about their warranty. If you install your own solar panels, even the smallest mistake can void your warranty. Then you’re stuck with a system that might not be working right, has no warranty protection, and still cost you some money to install while not generating any income.
4) Paperwork, Paperwork, Paperwork
It’s great to use green solar technology and do your part to improve the environment and reduce our dependence on oil. But there’s also a financial benefit, with federal, state and local solar tax credits and grants, not to mention getting Solar Renewable Energy Credits (SRECs).
Obtaining those tax credits, grants and SRECs can be a bureaucratic nightmare. There are numerous forms to fill out, certifications to be obtained, and other hurdles that the homeowner might have to jump through. And if you make a mistake on any of your forms, you have to start all over from the beginning. Doing all this yourself can add months—sometimes years—to the time it takes for you to see a financial benefit of your solar panel system.
A professional solar installer can help you get every single cent you deserve from your solar panels, while installing a higher quality product safely.
We don’t like to brag too much (after all, this blog is about more than our company), but here at Solar Energy World, we take pride in helping our customers through every step of the solar installation process. From the first free solar analysis, through the installation and inspection, to the processing of paperwork, we provide customers with a seamless experience that makes switching to solar easier.
Far easier than doing it yourself.
Prince Georges County Homeowner Reduces Carbon Footprint and Saves Cash
One of the systems we’re particularly proud of is a unique ground install in Bowie, MD. The Blackwells, the family who hired Solar Energy World, were facing a rather steep $7,550 annual electricity bill.
The Blackwell’s are the owners of a large single-family home built in 2006 in Bowie, Maryland. The two-story home sits upon an approximate 40,000 square foot lot. So, with available space, the Blackwell’s explored the use of ground mounted solar panels to reduce their energy costs.
Our solar analysis showed that the Blackwells that it pays to go solar. The family opted for a 10.32kW solar electric system that includes 48 – 215 watt ground mounted panels. After the federal tax credit, state grant and local property tax credits, the Blackwell’s expect their solar panel system to cost nearly 50% off of the total installation cost.
In addition to the government incentives, the Blackwell’s will be saving $2,471 per year on their electricity bills and earning $4,435 per year by selling their Solar Renewable Energy Credits; making their ground mounted solar electric system pay back in less than 6 years.
We also installed an Enphase monitoring system along with the solar panels. The monitoring system showed that in just the first 10-days of operation, the system produced 505 kilowatt hours; which could power 1,529 light bulbs, 505 computers and 15 homes for one day.
Powering up the Blackwell’s solar panel system also reduced their carbon footprint, with a carbon offset of 865lbs. Within the same 10-day period the offset equivalent of planting 10 trees, not consuming 45 gallons of gas, and not driving 26 cars for a day.
Not only that, but they look amazing. Check out these other pictures of the solar system or read the solar case study.
Back to Basics: How Many Solar Panels Do You Need?
This is one of the first questions people looking to install a solar panel system tend to ask. As we mentioned in our last Back to Basics post, one factor that determines how many panels you need is how much energy your home uses. Of course, this depends on how big your house is, how many electrical appliances you use and if those appliances have good Energy Star ratings.
According to the U.S. Energy Information Administration, the average household consumed 11,040 kWh (kilowatt hours) per year, or 920 kWh per month. Maryland, is slightly above that, with household consuming more than 1,000 kWh per month (see this spreadsheet for energy consumption information for each state).
Now, consider that a high-efficiency panel that’s 32 x 60 inches will generate 185 watts per year. That means that you would need approximately 60 panels if you wanted to cover your entire annual electricity usage (provided you consume the national average). And that would be 160 x 300 square foot roof!
Since very few of us have that size roof, we therefore need to make realistic expectations about the size of system we that we can really afford. To do that, we need to look specifically at your energy usage, the size of your roof and the amount of sunlight it receives. We then put all those numbers into a cost/benefit analysis to show you exactly how much you can save based on a realistic estimate of the size of the system your home can handle.
Sidenote: There’s far less financial benefit to purchasing lower-efficiency panels. Ultimately, they produce less energy, meaning that you need more panels to create the same amount of energy.
Back to Basics: Is Your House Is Solar Ready?
While it’d be great if everyone was able to install solar panels, not every home is ideal. Several factors go into whether or not your home is ready for a solar panel system.
When we come to your house for a free solar analysis, we consider three things:
- What you want to get out of a solar panel system (reduce your utility bills, reducing future costs of energy, improving the value of your home, etc.)
- What direction is your roof facing
- What your current annual energy usage is
The biggest factors that determine whether a solar panel system is right for you include the amount of energy you need, how much sunlight your system receives (remember, you roof should be southerly facing for maximum system efficiency), the size of the system your roof can accommodate and the amount of energy that system can produce.
Once we take into account all of these factors, we can determine if your house is solar ready. Plus, we’ll give you a solar cost/benefit analysis that will show you how much you’ll be saving by installing solar panels.
Where can you put solar panels?
“In the sun!” someone joked at one of our recent solar workshops. Yes, that might be the obvious answer, but it’s a little more complicated than that.
It actually depends on the type of system you want installed. Solar electric systems require light, while solar thermal systems require heat.
Generally, solar panels can be mounted on your roof, as long as the roof is southerly facing and does not have any shade from trees. This will ensure that your panels receive the maximum amount of sunlight throughout the year.
Other places to put solar panels include your garage (if it’s a separate structure), or perhaps a part of your yard that consistently receives sunlight. There are also ground mount and pole mount options.
Here are some photos of recent solar panel installations we’ve done.