Measuring Solar Panel Efficiency

In a climate of rising fear over dwindling fossil fuels, homes and businesses have begun installing solar panels to augment or replace their current energy systems. These panels are relatively simple to maintain, but dirt and improper placement can significantly decrease their power output. In order to ensure that you are obtaining the optimal value from this product, you should regularly check the efficiency of your solar panels. This is a simple procedure, requiring little more than multimeter, and it will maximize your savings.

First, you need to determine the area of your panels. If you don't have that data from the installation, just use a measuring tape.

Second, you need to figure out the maximum solar radiation for the exact spot on Earth where your solar panels are sitting. Essentially, this is a measurement of how much power the sun is bringing to your location — i.e., the maximum power your solar panels could theoretically provide, keeping in mind that current panels achieve only a maximum of about 20% efficiency. You can measure solar radiation with a solar meter, or you can look at the database on the National Renewable Energy Laboratory's website, which provides average solar input for various regions throughout the year. 

Now you need to figure out how much power your panel is actually providing. Use a multimeter to measure the voltage and current that your panel is producing, then multiply these figures to calculate the power produced (P = VA). Keep an eye on your units — your panel area should be in meters squared, and your power should be in kilowatts.

To determine your panel's efficiency, just divide the power output of your solar panel by the solar input of your location (both in kilowatts per meter squared) and multiply by 100. If the number is lower than it should be (around 20), you may need to clean your panel, adjust its angle or ask a professional to inspect it. 

Installing a Solar Panel at Home

These days, the cost of fuel rises almost as fast as concerns about global warming and funding for terrorists. Solar energy is becoming an attractive alternative to petroleum and coal, and you have probably even seen arrays of photovoltaic cells on large office buildings. Unfortunately, the trend is growing less rapidly in residential areas, largely because of the upfront cost, the aesthetics and the presumed hassle of installation. However, these disinclinations are generally misguided. While solar panels are certainly not cheap, there are a plethora of tax rebates available on state and federal levels, and the deduction -- or elimination -- of your electricity bill will pay you back and then some over time.

If you're particularly stingy and love breaking out the power tools, like my dad, you can lower the upfront cost of a panel even more by installing it yourself. Be advised that if you aren't an electrician or an avid do-it-yourselfer, this project probably isn't for you, and you will likely wind up saving yourself a lot of money, time and pain by simply calling in a professional. If you can use a ladder, a stud-finder and common sense, though, you can probably at least perform the basic setup.

The first step in setting up a solar panel is making sure you can legally install it. Check with your homeowner's association (HOA), unless you live in one of the following states, which have laws protecting solar access rights: Alaska, Arizona, California, Colorado, Delaware, Florida, Idaho, Maine, Maryland, Massachusetts, Nevada, New Jersey, North Carolina, Oregon, Vermont, Virginia and Wisconsin.

The following states have have guidelines that offer homeowners some leeway in installing solar panels, but you should still check: Georgia, Indiana, Iowa, Kansas, Kentucky, Minnesota, Missouri, Montana, Nebraska, New Hampshire, New Mexico, New York, North Dakota, Ohio, Rhode Island, Tennessee, and Utah.

If you live in one of the other states, start pressuring your government to grant you solar access rights, and in the mean time, be sure to check with your HOA before you install anything.

No matter where you live, you'll also need to obtain a building permit, so contact your local building authority (county and city). In some states, you actually have to be licensed to install solar panels. You will also have to have your solar panel inspected, and you will have to obtain permission from the power company to connect. (If you hire professionals, they take care of all this.)

The second step is to select the optimal spot for a panel. You want to put it in the place that will receive the maximum amount of sunlight at noon. Typically, this is the south facing part of your roof, but if you have several trees or a large shadow-casting building on the south side, you may need to hunt for a better spot. Also, you need to make sure your roof is sturdy enough to hold a panel, or you're going to wind up with a costly hole. You certainly don't have to install a panel on the roof; you can also put it on a pole in the yard, but these take up more space and are easier to see from the road (if aesthetic appeal concerns you).

In addition to where you put your solar panel, you will have to determine the optimal angle for your panel. The basic formula for this is adding 15 degrees to your latitude in the winter and subtracting 15 in the summer (yes, this means you have to adjust your panel throughout the year). If you really want to maximize your solar energy output, multiply your latitude by .9 and add 30 degrees to your latitude in the winter; subtract 2.5 degrees in the spring and autumn; and subtract 52.5 degrees from the winter angle in the summer.

When you have optimized the setup location and angle, you are ready to begin installation. Most solar panel kits come with a mounting apparatus. Typically, this involves two metal rails and a metal piece that screws into the panel and slides in between the rails, kind of like the sliders for a drawer. EasyJack and Tile Trac are the most common brands.

For the installation, you will need a stud-finder or the blueprints of your house, a drill with a pilot bit, steel bolts, a ladder, roof flashing or caulk, and of course a solar panel kit.

1. Use the stud-finder to find the studs on your roof. You can also look at your blueprints, but this is less reliable. You need to drill into studs because they offer the sturdiest support and are less likely to splinter or break.

2. Measure how far apart the holes on the mounting rails are, and drill holes in the studs this far apart. Use a pilot bit so you don't split the wood.

3. Line up the holes in the mounting rails with the holes you drilled and insert steel bolts through them. Seal the area around the bolts with roof flashing or caulk so your roof doesn't leak.

4. Put the mounting interface on the solar panel (each kit has its own straightforward instructions) and slide the interface into the rails.

5. Make sure the solar panel is at least 6 inches from the roof: this will give it proper ventilation and keep it operating efficiently (and keep it from starting a fire). Adjust it to the angle you calculated.

6. If you have background in electric work, connect the conduit of the panel to the inverter. If you don't know what that means, call a professional electrician.

You Don't Need Solar Panels to Harness the Sun

The sun is our most renewable resource, but currently, solar energy accounts for less than 1% of the world's energy consumption. While the solar industry is constantly growing, it is still in its early stages, and solar technology is not yet widely available or economically attractive. However, even if you aren't ready to invest in solar panels, there are still plenty of ways that you can take advantage of sunlight to conserve energy.

1. Adjust your windows according to the seasons. In the summer, keep your blinds down, and use light-colored shades to reflect the light. By preventing light energy from entering your house, you'll keep the ambient temperature down, so you can keep the air conditioning up. The opposite holds true for the winter: keep your shades up, use dark colors to absorb light, and make sure your windows are clean so that light can readily pass through.

2. Install semi-transparent skylights. This will allow you to use natural light during the day rather than electricity -- which is actually better for your eyes -- and it will provide heat. In the summer, cover your skylights with solar-screen awnings to keep the temperature down.

3. Large windows and light-colored paint will brighten rooms, allowing you to use less electric light.

4. Plant trees on the east and west sides of your house to block the sun during the summer, but keep the south side of your house clear to allow full sunlight to enter during the winter.

5. Grow plants in sunlight rather than under UV lamps.

6. Grow your own food. This cuts energy consumption significantly, because the food doesn't have to be transported, and you probably won't be using machines, pesticides and fertilizers to plant and harvest it.

7. Read, study and work near a window instead of a lightbulb.

8. Share electricity with others by sitting in the same room -- not only are you saving electricity by using one light instead of many; you're also bringing your family closer together.

9. Bask in the sun or grab a sweater instead of turning up the heat. You'll actually warm up faster, and you'll burn more sedentary calories.

10. If you're building a new house or remodeling an old one, take a few pointers from the architects of antiquity. In ancient times, artificial light was still an expensive, inefficient and often smelly technology, so buildings were constructed to make full use of the sun. Orient your rooms to let in maximum sunlight, and seal your house well to retain both your heat and your air-conditioning. Build on top of a hill to capture the cooling breezes if you live in a warm climate, but build into a hill to retain warmth if you live in colder zones.