Based on historical Portland, ME data, solar panels that are tilted towards the equator at an angle equal to the latitude will produce the maximum solar energy output in Portland.
Portland has an average monthly Global Horizontal Irradiance (GHI) of 3.83 kilowatt hours per square meter per day (kWh/m2/day), which is approximately 7% less than the average monthly Direct Normal Irradiance (DNI) of 4.14 kWh/m2/day. 
Solar installations in Portland that are always titled at the latitude of Portland (Average Tilt at Latitude or ATaL) average 4.63 kWh/m2/day, or about 21% greater than the average monthly GHI of 3.83 kWh/m2/day and approximately 12% greater than the average monthly DNI of 4.14 kWh/m2/day. 
Global Horizontal Irradiance: The total amount of solar radiation that is received per unit area by a surface that is always positioned in a horizontal manner.
Direct Normal Irradiance (DNI)
Direct Normal Irradiance: The total amount of solar radiation received per unit area by a surface that is always perpendicular to the sun rays that come in a straight line from the direction of the sun at its current position in the sky.
Average Tilt at Latitude (ATaL)
Average Tilt at Latitude: The total amount of solar radiation received per unit area by a surface that is tilted toward the equator at an angle equal to the current latitude. ATaL will often produce the optimum energy output.
Solar Radiation Levels in Portland
Solar Radiation Data in Portland, ME
See the chart below for monthly solar radiation levels in Portland.
* Amounts listed in kWh/m2/day (kilowatt hours per square meter per day)
Solar Radiation Analysis for Portland, ME
Portland, ME has a average annual solar radiation value of 4.67 kilowatt hours per square meter per day (kWh/m2/day). 
The month with the highest historical solar radition values in Portland is July with an average of 5.73 kWh/m2/day, followed by August at 5.56 kWh/m2/day and June at 5.37 kWh/m2/day. 
The three months that historically average the lowest average solar radiation levels in Portland (Maine) are December with an average of 2.92 kWh/m2/day, followed by November with an average of 3.12 kWh/m2/day and January at 3.64 kWh/m2/day. 
Solar Power Comparison: Portland vs. the U.S.
Solar Power Levels in Portland
The average monthly solar radiation level in Portland, ME, of 4.67 kilowatt hours per square meter per day (kWh/m2/day) is approximately 25% greater than the average level of 3.73 kWh/m2/day in a city with historically low levels (WA) and is approximately 29% less than the average level of 6.6 kWh/m2/day in a city with historically high levels (NV). 
→ Values listed as 0 (zero) are not available (N/A).
Solar Power: vs. the U.S.
Below is a month-by-month comparison of how average Portland solar radiation levels compare to average levels in a city with historcially high levels (NV) and a city with historically low levels (WA). 
→ k/m/d = kWh/m2/day = kilowatt hours per square meter per day.
→ Values listed as 0 (zero) are not available (N/A).
We do not currently have data on solar panel installations in the city of Portland, ME at this current time.
However, Portland is in Cumberland County and Cumberland County has at least 196 solar insallations right now. 
Solar Power Output in Portland
The Power of Solar in Portland, ME
Monthly AC solar system output averages for Portland (me). Month-by-month solar power, as ranked by AC output, in Portland. 
* Amounts listed in kWhac (kilowatt hours (AC))
Solar Output Analysis for Portland, ME
Portland (ME) has a average annual solar AC output value of 5529.05 kilowatt hours (AC). 
The month with the highest historical solar power output in Portland is July with an average of 545.85 kWhac, followed by August at 535.2 kWhac and May at 531.73 kWhac. 
The three months that historically average the lowest average solar output levels in Portland (Maine) are November with an average of 312.19 kWhac, followed by December with an average of 312.2 kWhac and January at 387.87 kWhac. 
Cost of Utilities in Portland
Portland Electricity Costs
Electricity prices (residential) in Portland averaged 16.01 cents per kilowatthour (¢/kWh) in September 2018, which was about 23% more than the overall U.S. average residential electricity rate of 13.01¢/kWh in September. 
Solar Power Poll: Portland
Vote now: Given all of the data and analysis provided for Portland, is solar power a good choice for residents of this city?
Portland Natural Gas Costs
Natural gas prices (residential) in Maine averaged $23.71 per thousand cubic feet (Mcf) in September 2018, which was approximately 37% more than the overall U.S. average residential natural gas rate of $17.32 per Mcf in September. 
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"Solar cells convert sunlight into electricity through a physical process known as the photovoltaic effect.",
"Nineteen-year-old Edmund Becquerel, a French experimental physicist, discovered the basis of solar energy in 1839.",
"Various missions to space by different countries are known to utilize solar energy as a main power source.",
"The largest solar power plant in the world covers 1000 acres & is located in the Mojave Desert in California.",
"Some tax incentives and rebate programs are designed to spur the use of solar energy. These vary by location.",
"Solar power is renewable, does not produce any pollutants and is one of the cleanest source of energy.",
"It takes light about 8 minutes, 19 seconds to travel the 93,000,000 miles from the sun's surface to us on Earth.",
"About half of the sun's energy is absorbed by the Earth's surface; about 30 percent is reflected back from the surface.",
"The solar energy that strikes the Earth in one hour could provide all of the Earth's energy needs for a complete year."
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