Question

If I install solar panels, will they support an all-electric house (4 BR 3 BA)?

Asked by shelley rodgers
Los Lunas, NM

I am considering purchasing an all-electric home. Water heating is evaporative cooler.

Answer

Shelley,

Prior to considering the installation of photovoltaic panels on a home, a thorough analysis of the home should be performed

The results from this analysis will properly direct you in the purchasing and installation of photovoltaic panels for your home to maximize its efficiency.

Items to consider:

  • Solar orientation
  • Existing building envelope
  • Energy consumption
  • Incentives
  • Type of photovoltaic panels

Solar orientation

This is the easiest to determine and key to the performance of any photovoltaic system.

  • Do you have a southern-facing roof slope? If not, a ground-mounted system will have to be installed. In many instances city ordinances prohibit this type of installation. Also, it increases the overall cost substantially due to necessary installation of foundations and mounting racks.
  • Obstruction: What is the nearest tall object which could cast shadows on the solar system? Look at trees near the home as well as taller homes. To help determine whether or not they will cast a shadow, refer to solar path and angle charts for your specific latitude to help determine the length of shadow for each object by month.
  • Insulation: Determine average duration of time of sunlight. For New Mexico you are between 6.0 and 6.8 hours of sunlight; this is really good. What this means is that, for example, a 4-kW photovoltaic system will generate approximately 24–27.2 kWh gross of electricity.

Existing building envelope

Is your existing home properly insulated? 

  • With the aid of a professional energy auditor, audit the existing home. This will determine both heat loss during the heating season and heat gain during the cooling season.
  • This analysis will pinpoint areas of inefficiency and areas of required building-envelope upgrades.

If your existing home is inefficient, installing photovoltaic panels is like placing a Band-aid on a sieve to prevent it from draining liquid.

Energy consumption

Review all energy bills for an entire year. This will give you a full understanding of how much energy is required to operate the home.

  • Also look at the existing systems to determine their efficiency and remaining life expectancy. When installing new equipment, look at purchasing Energy Star rated products.
  • Factor in the reduction in power consumption after any building envelope upgrades are performed. You do not want to install a photovoltaic system larger than what is required.

State, federal and power supplier incentives

Visit www.dsire.org. This is a U.S. Dept. of Energy database listing incentives from both state and federal governments. The list is extensive but worth the research.

For example, on a current project of mine here in Michigan,

  • my client will receive 50% of the installation and material cost from the power supplier plus the ability to sell back any power produced and not consumed.
  • Also, he will receive a 30% federal tax grant plus additional state tax incentives and exemptions.

These incentives will reduce his breakeven for a 4 kW system to just about 7 years with an approximate gross savings/earnings of $40,000 over the course of 25 years.

Type of photovoltaic panels

There are two predominant types of photovoltaic panels available: multi-crystalline and amorphous (thin film).

  • Multi-crystalline: These panels work best under full sun conditions and cooler temperatures. They are required to be installed on a rack system to allow for airflow below the panels to reduce their overall heat gain and maximize their performance. These panels do not lend themselves easily to Building Integrated design.
  • Amorphous: This is a thin film panel which is flexible and virtually indestructible. However, these panels are less efficient than the multi-crystalline panels, but produce a greater amount of power over a longer duration of time. They work well in low sunlight and high heat conditions, and produce electricity form ambient light as well as direct sunlight. They can be installed directly to standing seam metal roof panels, membrane roof systems. They come in many configurations, including shingles and strips.

A successful solar system

To recap, it is only through proper design and analysis that a photovoltaic system will be successful. There is no one solution or equation which can be applied to determine its capabilities and effectiveness on the reduction of your electrical consumption.

Refer to the green professional listings under “Find a Pro” in your area to assist you in making the right decisions.

 

For more information:

Read Evan Little's Q&A "When we purchase a home I would like to upgrade to solar. What does it take and how much does it cost?"

Tagged In: green cost, incentives

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