There is not a "one size fits all" solar photovoltaic (PV) system. In fact, solar PV arrays can vary considerably both in their general design, size and application. That is why it's important for consumers to clearly understand what they're looking for when shopping for a solar array. The two biggest considerations that consumers should take into account when selecting their solar PV system are related to the size of their system and what type of solar cell it has.
Selecting the right solar PV system can be everything from an investment standpoint - too small of a solar system and buyers, energy demands aren't met, too large of a system and buyers will over spend on a system that generates too much power and potentially fails to generate a return on their investment. So what should consumers do in order to get it right and select a solar PV system that meets their needs?
The first step consumers should take is to identify how much electricity they need or want their system to generate. Contractors may try to sell buyers as much generation capacity as will fit on their roofs, but buying too large (and expensive) of a system is one of the biggest pitfalls a consumer can make.
That said, some consumers may actually want to purchase an array that will cover their entire roof. This option is most suitable for consumers who want to take advantage of net metering policies. Net metering policies are utility rates that enable home and business owners to actually sell excess electricity generated by their solar PV system back to their utility company at an agreed upon rate. Typically, the rate is equal to what they pay per unit of electricity. Most states have net metering policies, although rates will vary state to state. In this way, the solar PV investment will not only meet some household energy demands, but also serve as an income generator for the solar PV owner. It's important to keep in mind that installing solar PV panels everywhere may not be effective since panels must be properly positioned to capture sunlight and kept out of any areas where there are obstructions or shade.
Rather than fill their entire rooftop, most consumers will want to purchase a system that offsets all or a portion of their electric bill. According to the United States Energy Information Administration (EIA), in 2011, the average American household used approximately 11,300 kilowatt hours (kWh) of electricity per year. However, since there are many factors that can make energy usage much higher or lower than that - building size, climate, heating and cooling type, number of luxury appliances, etc. - the best way to determine a home's unique energy demand is to review recent utility bills for that household. If consumers don't have their bills on file, they can also request this analysis from their utility company.
Electricity is typically measured in kilowatt hours. The first step is to find out what the household's annual kWh usage is. Since electric consumption may vary by season, it's important to look at an entire year's worth of bill payments to understand ebbs and flows in electric demand from month to month and season to season. For instance, consumers with electric air conditioning units may see huge spikes in electricity demand during warmer months whereas those in cooler climates with electric heating may have different demand patterns. Another major factor affecting energy usage is consumer behavior. Changes in the number of occupants in a household can cause electricity usage to go up or down, since more people means more water and appliance usage. Whatever the case, consumers should determine what their peak demand for energy usage is - peak energy usage is the amount of energy that the household consumes at the highest point throughout the year. Utility companies can send this data to customers if they have not have kept their utility bill statements on file.
Beyond overall demand, consumers will also want to consider what times of day they actually use the most power - morning, midday, or evening. This is important, because solar PV systems only generate power during daylight hours. The only exception to this is if a homeowner has or wants to invest in some type of energy storage system that enables them to use electricity generated from their solar PV system at any time of day. However, assuming a standard solar PV system without energy storage, buyers should identify what their electricity demand is during daylight hours so they can select a system that meets their demand during these hours. Daylight hours will vary by geographical location and even by season so consumers should understand local conditions. There are many websites online that can provide information about average daylight hours and changes in daylight hours by geographic location.
As a general rule of thumb, the cost per kilowatt hour of a system goes down slightly as it increases in size, so consumers should also take this into account. This is largely because inverters - an essential component of a solar PV system package that converts the electricity to the right type of current - are often sized to accommodate a solar PV system that is larger, say 5 kW. In this way, the same inverter is often used for a smaller systems, such as a 3 kW system - so the costs for the inverter might be slightly more for the smaller model. This is something to factor in when considering the size of a system to buy.
Another major consideration is what type of solar cell you want within your PV system since different modules generate different levels of electricity per square foot than others. At a very basic level, monocrystalline silicon systems have traditionally been known for being the most efficient type of solar cell - generating the most electricity relative to size; however, they are also the most expensive. Polycrystalline silicon cells are less efficient than monocrystalline arrays, but they're also less costly. And they are a particularly good choice for climates that have more overcast days. Finally, thin film technologies are also a new option that are becoming increasingly popular - they're typically as efficient as polycrystalline models and are very cost-competitive. And with lots of research and development being put towards thin film technology, this type of solar cell is likely to drop in cost even further in future years.
The best way for consumers to determine what solar PV system is right for them is to hire an energy auditor who is cross-trained in solar PV. These professionals can provide a detailed assessment of a household's energy usage and offer tips that are tailored to the consumers' individual needs. Energy audits typically cost just a few hundred dollars. And many utility companies or state energy offices now offer rebates that cover some or all of the costs of energy audits - this level of analysis can give consumers the answers they need when selecting the right size and type of solar PV system to buy.