One Planet Solar & Wind LLC
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How do I know how what size system I will need?
There is no one right size for photovoltaic systems. Every site is different and the needs of system
owners vary, too. System size depends on several factors, including how much electricity (in kilowatt-
hours or kwh) you consume, the orientation of the system, the tilt of the system, available space and
funds.
The first step to determining the size of the photovoltaic system you'll need is to reduce consumption.
Saving electricity is typically cheaper than generating it. Also, the smaller your overall consumption, the
smaller and cheaper the system you'll need.
I have a “?” sq. ft. home. How much will a system cost?
The size of your home is not the issue, but rather what your average electricity bills are and how much
of that average bill you would like to offset. How much you want to offset will dictate the system size
and cost.
How much space will the solar electric system take up on my roof?
A good rule of thumb is to allow 100 sq. ft. per every kilowatt of electricity the system produces. A
solar electric system for a typical home will require 300-500 sq. ft.
How long will my solar system last?
Most solar panels come with a 25 year power output guarantee and are expected to last at least twice
that long. The power output guarantee on the solar panels is provided by the manufacturer of the
panels and states that at the end of the 25th year, the solar panel will still produce a minimum of 80%
of their original power output.
Will my system have batteries?
Usually only if the system is 'Off-Grid'. Batteries will be essential for the storage of electricity so you
can use electrical equipment when there is no sunlight. Grid Connected PV systems don't need
batteries, however, you can have batteries with a grid connected installation if you wish to have power
during power cuts, you need to determine this before the installation.
What happens during a power outage?
With a grid connected solar PV system, the inverter will automatically disconnect itself from the utility
grid when there is a power outage. This is to prevent back feeding the grid and putting engineers
working to restore power in danger. But, if you have a grid connected PV system with battery back up
it will automatically switch to backup power with little detection. Both these systems will automatically
hook back up to grid once power is restored.
Does PV add to the Resale Value of my home?
PV "System Resale Value" for your home is based upon research published in the Appraisal Journal
which concluded that "The increase in appraisal value for a home is about twenty (20) times the annual
reduction in operating costs due to energy efficiency measures.". To calculate System Resale Value the
first year annual utility savings is multiplied by twenty (20). Source: Appraisal Journal, Nevin/Watson.
What is the payback?
Payback is immediate, if you were to finance your solar system your payments would typically be less
than the electric bill that it replaces. A solar system will also add value to your property, reduce your
monthly expenses and insulate you from higher and higher energy costs. If you were to pay cash for
your system, at today’s rates, you will typically recover all your investments within the next 6-10 years,
but as rates go higher the time it will take to fully recoup your investment could easily be less than 5
years.
How big is a typical system?
Solar PV systems range in size from fifty to four hundred square feet. A system composed of high
efficiency cells will produce 1kW per hour for every 100 square feet.
How do I know if my site will work for a PV system?
Solar designers look for sites that provide an optimal southern orientation, good exposure to the sun,
and an adequate amount of structural support and space for solar panels to be placed.
The best location for a PV system is on a south facing roof. Flat roofs provide an environment for a
variety of solar modules. Locating the PV system on the ground can work with either a fixed mount or
a tracking mount system. If the space or the solar exposure for a PV system is limited, consider going
to a system with a higher efficiency rating. They are more expensive but make more energy with less
square footage of module space.
Can my Homeowners Association (HOA) place restrictions on the installation
of a PV system?
Not usually. There are bills in most states that will prevent homeowner associations from blocking
improvements that save energy. These bills were enacted because the legislature found that some
homeowners associations were unreasonably restricting things like solar panels and evaporative
coolers.
Can PV systems produce power on cloudy days?
Yes. Although a PV system may receive 80-90% less sunlight on a cloudy day, the modules can still
generate electricity.
Do PV systems work well in the cold?
Yes. In fact, photovoltaic systems generate more power when the temperature is lower. Because of
the shorter hours of daylight and lower angles of the sun in winter, PV modules do generate less energy
than in summer.
Are PV Systems Safe?
Solar panels are a quiet, non-polluting source of energy. Like all large electrical devices, PV systems
generate electricity and should be treated with care and maintained with the assistance of a solar
professional.
Is the "Tilt" of my solar array important?
The Earth is tiled on its axis at 23.5 degrees and regardless of where you live the difference between
the sun’s peak angles in the sky from December to June is 46 degrees. Regions closet to the poles
experience seasons when the sun never shines, and six months later, seasons when the sun never goes
below the horizon.
The optimum elevation angle for your solar system depends on your latitude. In general the optimum tilt
angle is equal to you latitude, for this will ensure the maximum amount of sunlight over the course of a
year. Even better would be to manually change the elevation of your solar collectors over the course of
a year to follow the sun’s elevation in the sky.
A typical roof angle is 18 to 32 degrees. As long as the collector angle (known as "tilt") is at least 18
degrees up from horizontal, additional tilt usually has little effect on total year-round performance. An
exception would be areas with very sunny winters (as in most areas of Colorado) where a higher
angle, facing the collector more directly into the winter sun, can make quite a difference.
There is no one right size for photovoltaic systems. Every site is different and the needs of system
owners vary, too. System size depends on several factors, including how much electricity (in kilowatt-
hours or kwh) you consume, the orientation of the system, the tilt of the system, available space and
funds.
The first step to determining the size of the photovoltaic system you'll need is to reduce consumption.
Saving electricity is typically cheaper than generating it. Also, the smaller your overall consumption, the
smaller and cheaper the system you'll need.
I have a “?” sq. ft. home. How much will a system cost?
The size of your home is not the issue, but rather what your average electricity bills are and how much
of that average bill you would like to offset. How much you want to offset will dictate the system size
and cost.
How much space will the solar electric system take up on my roof?
A good rule of thumb is to allow 100 sq. ft. per every kilowatt of electricity the system produces. A
solar electric system for a typical home will require 300-500 sq. ft.
How long will my solar system last?
Most solar panels come with a 25 year power output guarantee and are expected to last at least twice
that long. The power output guarantee on the solar panels is provided by the manufacturer of the
panels and states that at the end of the 25th year, the solar panel will still produce a minimum of 80%
of their original power output.
Will my system have batteries?
Usually only if the system is 'Off-Grid'. Batteries will be essential for the storage of electricity so you
can use electrical equipment when there is no sunlight. Grid Connected PV systems don't need
batteries, however, you can have batteries with a grid connected installation if you wish to have power
during power cuts, you need to determine this before the installation.
What happens during a power outage?
With a grid connected solar PV system, the inverter will automatically disconnect itself from the utility
grid when there is a power outage. This is to prevent back feeding the grid and putting engineers
working to restore power in danger. But, if you have a grid connected PV system with battery back up
it will automatically switch to backup power with little detection. Both these systems will automatically
hook back up to grid once power is restored.
Does PV add to the Resale Value of my home?
PV "System Resale Value" for your home is based upon research published in the Appraisal Journal
which concluded that "The increase in appraisal value for a home is about twenty (20) times the annual
reduction in operating costs due to energy efficiency measures.". To calculate System Resale Value the
first year annual utility savings is multiplied by twenty (20). Source: Appraisal Journal, Nevin/Watson.
What is the payback?
Payback is immediate, if you were to finance your solar system your payments would typically be less
than the electric bill that it replaces. A solar system will also add value to your property, reduce your
monthly expenses and insulate you from higher and higher energy costs. If you were to pay cash for
your system, at today’s rates, you will typically recover all your investments within the next 6-10 years,
but as rates go higher the time it will take to fully recoup your investment could easily be less than 5
years.
How big is a typical system?
Solar PV systems range in size from fifty to four hundred square feet. A system composed of high
efficiency cells will produce 1kW per hour for every 100 square feet.
How do I know if my site will work for a PV system?
Solar designers look for sites that provide an optimal southern orientation, good exposure to the sun,
and an adequate amount of structural support and space for solar panels to be placed.
The best location for a PV system is on a south facing roof. Flat roofs provide an environment for a
variety of solar modules. Locating the PV system on the ground can work with either a fixed mount or
a tracking mount system. If the space or the solar exposure for a PV system is limited, consider going
to a system with a higher efficiency rating. They are more expensive but make more energy with less
square footage of module space.
Can my Homeowners Association (HOA) place restrictions on the installation
of a PV system?
Not usually. There are bills in most states that will prevent homeowner associations from blocking
improvements that save energy. These bills were enacted because the legislature found that some
homeowners associations were unreasonably restricting things like solar panels and evaporative
coolers.
Can PV systems produce power on cloudy days?
Yes. Although a PV system may receive 80-90% less sunlight on a cloudy day, the modules can still
generate electricity.
Do PV systems work well in the cold?
Yes. In fact, photovoltaic systems generate more power when the temperature is lower. Because of
the shorter hours of daylight and lower angles of the sun in winter, PV modules do generate less energy
than in summer.
Are PV Systems Safe?
Solar panels are a quiet, non-polluting source of energy. Like all large electrical devices, PV systems
generate electricity and should be treated with care and maintained with the assistance of a solar
professional.
Is the "Tilt" of my solar array important?
The Earth is tiled on its axis at 23.5 degrees and regardless of where you live the difference between
the sun’s peak angles in the sky from December to June is 46 degrees. Regions closet to the poles
experience seasons when the sun never shines, and six months later, seasons when the sun never goes
below the horizon.
The optimum elevation angle for your solar system depends on your latitude. In general the optimum tilt
angle is equal to you latitude, for this will ensure the maximum amount of sunlight over the course of a
year. Even better would be to manually change the elevation of your solar collectors over the course of
a year to follow the sun’s elevation in the sky.
A typical roof angle is 18 to 32 degrees. As long as the collector angle (known as "tilt") is at least 18
degrees up from horizontal, additional tilt usually has little effect on total year-round performance. An
exception would be areas with very sunny winters (as in most areas of Colorado) where a higher
angle, facing the collector more directly into the winter sun, can make quite a difference.
