Project

The roof on this house faces south, which is ideal for solar panels. ©2015 Robin Rogers / Solaripedia

Do You Have a Suitable Location for Solar Power?
There are three main factors that determine whether a specific site is good for solar power: the general geographic location, site-specific features, and local regulations for residential PV systems.

Geographic Location
An important factor to consider when installing a photovoltaic array on any property is its relative location to the geographical poles of Earth. In general, the total hours of sunlight received during the course of a year are higher in tropical locations and lower in places close to the poles. You have probably also noticed the seasonal effect as days become shorter in winter and longer in summer - and that this effect becomes more pronounced as you move farther to the north or south?

Yearly solar radiation is measured in peak sun-hours, and this value is directly related to the energy output of solar photovoltaic systems and the monetary savings they can yield. For example, if you take two PV systems of equal nameplate capacity, and place them in two separate locations with respective radiation rates of 2000 and 2500 peak sun-hours per year, the latter will yield 20% more energy and cash savings.

NASA has a free web resource called the Atmospheric Science Data Center, where you can input your coordinates to get the average peak sun-hours per day at your location. Simply input your latitude and longitude, click “Submit”, and navigate to the section called Parameters for Tilted Solar Panels. For the total yearly radiation, multiply the average daily value by 365.

Site Specific Conditions That Affect PV System Performance
Shadows are the enemy of solar PV systems. You can live in the sunniest place on the planet, but a solar array will not produce much energy if permanent shadows are cast on it by a group of trees or a tall building.

Analyzing the impact of shadows on a specific site is a complex task that should be performed by professionals, but you can get a rough idea beforehand. Visit the location where the PV panels are desired at several different hours during the course of one day. Note where the shadows fall, hour by hour. Shadows that are large or dark will interfere with the production of power from a solar PV system located on that spot. There are different ways to mitigate the effects: cut down trees, move the PV array, for example.

Local Regulations for Solar Power
Finally, research local laws to ensure that they are favorable for solar power. Many governments now incentivize homeowners to go solar by offering tax benefits, and utility companies may offer rebates and performance payments. On the other hand, some governments protect utility companies by introducing fees and additional taxes for PV systems, or may even forbid their connection to the local grid.

Until 2018 in the USA, there is a federal tax credit for 30% of the PV system’s installed cost, regardless of where you live. Other incentives may apply, too, and the Database of State Incentives for Renewables & Efficiency (DSIRE) offers an up-to-date list of solar and other renewable energy incentives and rebates by state.

Analyzing the Financial Performance of a PV System

The financial performance of a solar photovoltaic system depends on the balance between cost of ownership and yearly savings achieved.

• Incentives such as tax credits and rebates reduce the cost of ownership.

• Abundant sunshine and high electricity price translate into increased yearly savings.

You can do a quick financial analysis for your project by using this calculator. Just input four basic bits of information – your state, current monthly electric bill, and whether or not your roof is shaded - the financial analysis is a single click away. And keep in mind that most solar panels come with a 25-year warranty with a life expectancy of more than 40 years.

Grid-Tied or Off-Grid System?
A grid-tied solar system is hooked into your local electric utility company’s system. Most residential homes use this system because your varying energy needs are covered by the utility if your system under or over-produces – that is, your home will use power from the utility when needed. If your system produces more energy with your solar panels your home uses, the excess energy is sent to your power company, allowing you to build credit in a process called net metering. In a grid-tied system, it is not necessary for you to have expensive back-up batteries to store the energy because the utility does it for you.

If your solar system is not connected to the utility company in any way, it is called being off-grid. If your home is 100% self-sustaining for its energy use, you do not have to worry about power grid outages. However, it would be necessary to install a battery back-up system to store energy for cloudy and you would need to dedicate space to storing the expensive batteries.

Your solar supplier and installer can help you determine which will work best for you.

Finding the Best Solar Installers at Your Location
Solar installers should have a business license (typically general contracting, electrician, home performance or home improvement) and liability insurance, at a minimum. Certification is highly desirable, too, by the North American Board of Certified Energy Practitioners’ (NABCEP’s) Solar PV Installation Professional Certification. Many state and utility incentive programs require NABCEP Certification and many public and private requests for bids require or strongly prefer NABCEP Certified installers.

The benefits of hiring licensed and reputable professionals include:

• Familiarity with electrical codes to help ensure your installation will comply.

• Experience connecting solar PV systems to the local grid that allows them to complete the project with minimal hassle.

Comparing several quotes is recommended to ensure that you’re getting a reasonable deal and high quality.

Resources

Solar Nation (USA)