There are two questions here, the first dealing with economics and the second with renewable energy systems.
It would be to your advantage to separate the rental home from the main home and your residence. This will remove the burden of estimating the amount of energy consumed by the rental, allow for accurate billing and remove any possibility of underpayment which would increase your liability to pay the remainder of the bill.
Next, if these two homes are on one lot, it would be in your advantage to review your local power company's requirements/restrictions for incentives for private renewable energy systems. You can view your state's incentive programs at www.dsireusa.org. If it only allows one plant per address, it may be in your best interest to install one system which then acts as a power plant for both homes. This will also allow you to charge your renter for power produced, making you the power supply or partial power supplier for that home. This ability to charge for the power supplied will reduce the return on investment for the installation and materials of the renewable power system.
Renewable Energy Systems
You are on the right track to consider upgrades first, before considering the feasibility of a solar system. Here are the items for consideration when looking at installing a solar system.
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 that 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 per month.
Insulation. Determine average duration of time of sunlight. For Nevada you are between 5.5-7.5 hours of sunlight; this is really good. What this means is that, for example, a 4 KW photovoltaic system will generate approximately 22-30 KWh gross of electricity.
Existing building(s) envelope.Is your existing home properly insulated?With the aid of a professional, perform an energy audit of 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 for both homes.
- This will give you a full understanding of how much energy is required to operate the homes. 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.
- Also look at 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.
- 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 return on investment for a 4 KW system to just about 7 years with a 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. These panels are less efficient then the multi- crystalline panels, but produce a greater amount of power of a longer duration of time. They work well in low sunlight and high heat conditions, and produce electricity from 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.
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 list of solar installers under "Find a Pro" to assist you in making the right decisions.