Photovoltaic (PV): photo = light, voltaic = producing electricity
PV systems, also referred to as solar electric systems, convert sunlight into electricity for your home or business using primarily semiconductor technology. As sunlight strikes the PV cells, it causes electrons to flow, creating an electrical current (photovoltaic effect).
How Does PV Work?
- Individual photovoltaic (PV) cells, or modules, are embedded onto panels. Sunlight striking the panels is converted into direct current (DC) electricity.
- The DC electricity goes to an inverter that transforms it into alternating current (AC) for household use.
- The utility meter records the net amount of energy generated through the PV system. When the system creates more electricity than used, the meter will spin backward and the excess electricity is released onto the electric grid. This helps offset the cost of electricity usage at night or on cloudy days when PV systems are not producing electricity.
Main components of a PV system
Modules/panels – The most common solar technology is rigid panels with crystalline silicon modules, making up more than 93% of the market. They have the longest track record, over 50 years, and have the highest efficiency ratings. Another option is thin-film PV that comes on a flexible panel that can be applied to many different surfaces and materials. It is commonly incorporated into the construction of a building, for instance, as roofing tiles or on the building facade.
Inverters – Typically, there is one individual, central inverter per array. This is the older, more proven technology, but has performance limitations. The alternative is microinverters with one smaller inverter per panel, which makes them more tolerant to shade, gives more flexibility in design and allows for easier future additions.
What size of system should you install?
Every site is different, and the needs of the system owner vary. System size depends on several factors including how much electricity (kWh) is consumed on-site, the orientation and tilt of the system and the available space and capital.
The first step is determining the annual kWh consumption of your home or business. Once calculated, you can pinpoint avenues on how to reduce your energy consumption by implementing energy-efficient improvements, a necessary step before installing solar.
By reducing your kilowatt-hour consumption, you will likely be able to install a smaller PV system, providing lower up-front costs and a shorter payback. Appropriately sizing your solar electric system is the key to a better return on investment.
The production of a proposed system should be parallel with the consumption on-site and not oversized. According to AB 920, your utility is required to purchase excess generation. However, the excess generation is purchased at a reduced rate of $0.04/kWh, far lower than typical kWh rate charges.
Remember that you do not have to offset 100% of the consumption of your home or business. Offsetting any portion can be beneficial and a good way to get started with solar. A rule of thumb is to divide your annual consumption (kWh) by 1700 kWh/year (1kW of solar will generate about 1,700 kWh/year). This will give you an approximate system size to base your design on.
Your residence consumes 6,000 kWh/year.
6,000 kWh/1,700kWh = 3.5 kW
This means that a 3.5-kW solar electric system would offset 100% of your energy consumption.
Will monitoring be included in my purchase or lease?
If you purchase a PV system, monitoring may or may not be included, but available at an additional cost. If you lease the system or enter into a power purchase agreement (PPA), monitoring will be included in the package.
Do solar panels and inverters come with a warranty?
Solar panels come with a 25-year production warranty. An inverter comes with a 10-year warranty. Most inverter manufacturers offer a supplementary 10-year extended warranty at an additional cost.