Question

I want to convert my home to solar energy. Should I install panels on the roof or build a trellis?

Asked by Mark Conrad, Venice, CA

I want to put solar panels on my house. I could install them on the roof or build a trellis. I also want to "spin backwards." What do you recommend?

Answer

Cynthia Phakos

Answered by Cynthia Phakos

Los Angeles, CA

Koffka Phakos Design

June 19, 2007

There are three issues I recommend you consider:

  1. surface area of the solar panels
  2. surface area of your roof
  3. orientation and angle of the sun

Surface area of the solar panels

First, determine the total surface area of the panels you want to install.

You will need about 80 to 100 square feet of solar panels for every kilowatt you are looking to produce yearly. Some residential "starter systems" are as small as 50 square feet; others can take up as much as 1,000 square feet.

Surface area of your roof

Next, consider the surface area of your roof and the availability of unshaded area there and on the rest of your property.

To receive the rebates that some municipal power providers offer, 90 percent of your solar panels have to be in full sun for the course of the day.

Orientation and angle of the sun

Finally, you need to keep in mind the orientation and angle of the sun at your latitude.

  • The best tilt angle for your solar panels is usually equal to your latitude, facing south.
  • Your home, in Venice, Calif., is at latitude 34° N, so the ideal tilt angle for your solar panels is 34°.

The sun’s position varies depending on the time of year; tilted at this angle, the panels will be perpendicular to the sun twice a year between equinoxes. If you install panels in a location where you cannot achieve the correct angle, you will lose some efficiency.

Get good help

I recommend that you seek the advice of an experienced architect to help you design an arrangement for your panels that works visually while also maximizing efficiency.

In addition, a reputable solar consultant can walk you through the pros and cons of the panels on the market and their efficiency versus cost and life expectancy.

Net metering

Regarding your desire to "spin backwards": What you are referring to is commonly known as net metering.

  • Net metering is an incentive in which customers with renewable energy systems are paid at retail rates for the additional electricity they generate.
  • Net metering is available in 43 states, including California.
  • A bidirectional meter is installed to track the difference between the amount of electricity you produce and the amount you consume.
  • At the end of each billing period, you receive a credit for any excess energy you have supplied to the utility power grid.

The Database of State Incentives for Renewables and Efficiency (DSIRE) provides a list of net metering rules by state.

 

For more information:

Get Your Power from the Sun, a consumer guide to solar energy from the U.S. Department of Energy, explains how to determine the size and location of your photovoltaic system, how to select a provider, and how to take advantage of renewable energy incentives to defray costs.

The U.S. Department of Energy also has a webpage about net metering.

The Solar Umbrella House, designed by the firm Pugh-Scarpa in Venice, Calif., is an interesting example of solar panels used as a trellis covering that shades the outdoor roof deck and the house.

Tagged In: incentives, solar panels

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