About Solar Electric (PV)
Watch our video demonstration and read our information below
Question: How does it work?
Answer: Photons from sunlight hit electons on the solar panel and cause the electrons to move, generating electricity.
Question: Are there different types of solar electric systems?
Answer: Yes. One type is a grid-tied system (net-metering, battery-less). This is the most popular system and is currently the only system EnergyWise installs. It is a system mainly for urban and suburban city-dwellers. All electricity that is produced is stored with the utility company. Another type is an off-grid system (battery based). This system is mostly for rural residents. Electricity is stored in batteries and used when needed. A third type is a hybrid system (battery-backup). This system acts just like a grid-tied system, except in blackouts. During a blackout, the homeowner still has electricity from batteries with stored electricity or a backup generator.
Question: I would like to have solar panels on my house, but what makes up a solar electric system?
Answer: Basically, silicone photovoltaic (PV) panels, a rack to attach the panels to the roof or ground, an inverter(s) to make usable electricity (dc to ac), disconnect switch(s) for safety, and electrical parts. Everything except the panels are called balance of system(BOS) components. If you have an off-grid or hybrid system, you will need batteries and a controller also.
Question: What about efficiency?
Answer A: Solar panels are not as efficient as most people would like. Some of the best panels on the market, Sanyo, have an efficiency of only 17%. Amorphous solar panels have an effieciency of less than 10%. Derating is calculated by PV Watts, maintained by the National Renewable Energy Laboratory (NREL). It offers a way to verify derating values of a complete solar electric system. It takes into account DC Rating, tilt angle, array azimuth, array type, module mismatch, dc to ac, soiling, shading, age, and other inefficiencies in a given system. Traditional derating factors range from .70 to .77, but with exclusive Enphase micro-inverter systems, we have a derating factor of only .819.
Answer B: Another key to efficiency is the sun-hours in a given day. Every major city in the United States has a specific number of sun-hours each day. For Oklahoma City, we have 5.5 sun-hours each day. This takes into account historical rainfall, cloudy days, and the sun’s angle at different times of the year.
Question: Is the payback any good?
Answer: There are several sides to this question. First, payback at the current rate of 10 cents/kwh is dismal, with about a 20-25 year payback period. Current tax credits are helping to lower that payback period, making it a better investment.
However, if electricity ever increases in price, your investment becomes more justified. A recent national study quoted in Home Power magazine stated that utility rates increase at an average rate of 4.4% per year, but the cost of your free solar energy, once installed, will never go up!
Question: What about the shape of my roof and the condition of my shingles?
Answer: The best placement for a solar system of any kind is on the south slope of a roof. A great median roof pitch for solar electric in Oklahoma is 8/12. The less shade from trees the better. If your roof is in terrible condition, the best time to install a solar energy system is AFTER a new roof is installed. Not only will flashings and openings in the roof not cause leaks, you will have the opportunity to install a long lasting or permanent roof with a long-term, zero-maintenance solar energy system.
**********Example*************
A 1 KW solar electric system would produce an average of 5.5 KW/hr. a day in Oklahoma City (1 KW x 5.5 sun hours = 5.5 KW/ hr).
After factoring in derating, we find that in reality it will only produce 4.5 KW/hr. a day in Oklahoma City (5.5 KW/hr. x .819 = 4.5 KW/hr.)
Since the average number of days in a month is 30.5, our 1 KW solar electric system will produce 137 KW/hr. average per month in OKC (4.5 KW/hr. x 30.5 days in month = 137 KW/hr. a month).
This means that in Oklahoma City, if you use an average of 1000 KW/hr. of electricity a month, this system would produce roughly 14% of your electricity from the sun!! (137 KW/hr. / 1000 KW/hr. a month = 14% offset)