Solar Energy for your House

What is the first step you should take when looking into solar?

Your first objective when considering solar alternatives is to understand how much electricity you use, what you are using it for and when you are using it.

• Pull out your electricity bills. What has your kWh usage been for each of the last twelve months? How much are you paying for electricity? What rate plan are you on? This information is critical to conservation, energy efficiency efforts and to proper sizing of a solar electric system.
• Do an energy efficiency audit. Many power companies offer this service for free. PG&E offers free energy audits to its customers online at http://www.pge.com/myhome/saveenergymoney/analyzer/. You can check with your local provider to see if this service is available for your property.
• Print out the audit results. If you do decide to go solar, a copy of the audit will need to be submitted with your solar rebate application.

Why does it matter when you use most of my energy?

• You receive a credit for the electricity that you feed to the grid. A solar electric system that is tied to the electrical grid feeds electricity into the grid when the system generates more electricity than you use. . You can then draw on electricity from the grid using the credits. Your electrical use is calculated over a twelve month true up period. This is called “net metering”.
• Take advantage of lower electrical rates during "Peak Usage" times. PG&E offers several Time of Use (TOU) rates for which it charges more for electricity during peak hours occurring weekday afternoons, and less for electricity during off peak hours. TOU metering often works well with solar electric systems. These systems generate electricity during peak times crediting the homeowners account at the higher rates. If the homeowner uses most of her electricity during off peak hours, she then draws against those credits at the lower rates, allowing her to use more electricity than her system generated because she is using it at times when the rates are cheaper. If you are home and using power during the afternoon, investigate different rate schedules.

A solar contractor can help you determine which rate schedule is best for your electricity usage patterns.

Is my home a good place for a solar electric system?

Shading, roof orientation, the amount of space on a roof and the quality of the roof are all factors which need to be considered.

• You want to install a solar electric system in a location which is free from shading. Shading is a significant factor. A fairly small amount of shade on one panel can greatly affect the production of each panel that the shaded panel is electrically connected with (similar to how a kink in a hose slows down the flow through the rest of the hose). Ideally, you should have unobstructed sun from at least 9am-3pm.
• Ideally, a solar electric system should be placed on a roof which is oriented south or west. Roof orientation and the angle of the solar electric system will affect the amount of electricity your system produces, and are factors considered in calculating your state rebate.
• Make sure your roof is in good condition. Solar panels have performance warranties for twenty-five years and systems can last much longer. You don’t want to have to take the system down to fix the roof. Oftentimes, you’ll want to reroof at the time you put a solar system up.

A solar installer will come out to your home to do a site analysis and will take each of these factors into consideration when providing you with a proposal of a system size, the system’s estimated performance and installation cost.

Solar Electric System Installation Basics

How does a solar electric (photovoltaic) system work?

Simply put, photovoltaics (PV) work by converting light energy into electrical energy. The PV cells consist of a positive and a negative slice of silicon placed under a thin slice of glass. As the protons of the sunlight beat down onto the photovoltaic cell they knock the neutrons off the silicon. The negatively-charged free neutrons are attracted to the silicon but are trapped by the magnetic field that is formed from the opposing fields. Small wires on the silicon catch these neutrons and when connected in a circuit an electric current is formed.

For greater detail:

• PG&E description of a grid-tied system http://pge.com/about_us/environment/solar/about_solar_energy.html

What does installation entail?

The installation process is fairly straightforward. The equipment used varies by roof type and installation company but the universal components are the panels, a support structure for the panels, an inverter, electrical pipe called conduit, and AC/DC disconnect switches. As with anything in the construction industry, each installation is unique, but we have provided a generic example.

On the roof:

• Posts called stand-offs are lag-bolted into your roof’s supports beams (flashings and sealants are used to protect any roof penetrations)
• Racking is attached to the standoffs in rows.
• The solar panels are positioned and bolted to the racking.
• Panels are wired together and connected to wiring that runs down to the inverter in conduit pipe (depending on your situation, the conduit may go through the attic or on the outside of your home).

Ground floor:

• An inverter that converts the DC power from the panels into AC power for your residential use is mounted (typically in your garage or on an outside wall in a relatively shady position).

**If required by your city, a disconnect switch is mounted near the inverter.

• Wires from the roof go into the inverter, then to your main electrical panel or subpanel.
• System is turned on and net-metering begins.

How long will installation take and do I have to be home?

A typical residential installation should take 2-5 days and you do not necessarily need to be home as long as the installation crew has the necessary access.

How big of a system will I need?

• First determine what portion of your current electrical needs you would like your system to meet. Typically homeowners choose to cover 50-85% of their total electrical bill.
• Give a reputable solar company your electric bills. They will use their analysis tools to provide you with a proposed system and corresponding financial analysis and they will take other considerations (such as roof area) into account as well.
• Consider any expected decreases/increases in your electrical usage (i.e. a child moving away from home, spa installation, etc.).

How long will my system last?

Nearly all solar panels are guaranteed to produce for 25 years and most inverters have a 10 year warranty. This can vary however and is something you should talk to your installer about. Even though most inverters will exceed their warranted 10 years of use, you should expect to replace the inverter during the life of the system (price range: $1,500 - $4,000).

The Benefits of Going Solar

The environmental benefits

The environmental benefits of solar electricity are many. Most basically you:

• Reduce your dependence on foreign oil imports
• Reduce your contributions of greenhouse gases to the atmosphere
• Reduce local air pollution
  

Other than it you may think many more benefits if you are living in a crises of power.