Solar Energy 101

People have used solar power for a very long time. Many old buildings face south to maximize passive solar energy for light and warmth. Active solar energy, which people harvested with devices like photovoltaic panels and solar thermal collectors, became popular around 1860, when scientists first suspected that fossil fuels would eventually become scarce.

A solar panel contains a collection of solar cells that use light energy from the sun to generate electricity. Solar panels for home systems are typically rooftop solar panels. Portable solar panels are available for use with solar generators or when you’re away from home.

Monocrystalline solar panels and polycrystalline solar panels are the two primary types. A monocrystalline panel uses one silicon crystal to form each solar cell. These panels are more expensive, but they’re also more efficient than other types. If a solar panel appears black, it’s probably monocrystalline. Polycrystalline panels use solar cells formed from many pieces of crystal. These panels are less efficient and require more space, but they’re an economical option. You can identify a polycrystalline panel by its bluish tint.

There are also amorphous solar panels, but they’re less efficient than other types. You’ll often see these panels on individual solar-powered devices such as an outdoor light or a mobile device charger.

See our guide to solar panels for tips on choosing the right devices for your application.

While solar panels won’t last forever, it’s typical for them to last from 20 to 30 years. However, their ability to generate power decreases over time. For example, after 20 years you can expect solar panels to lose about 10% of their original power output. The actual life span will depend on how much extreme weather your area gets, how often you clear dirt and debris away from the panels and how often you inspect them for loose mountings, damaged wiring, etc. And of course, high-quality solar panels and solar panel installation are significant factors in how long a system will operate efficiently.

In a home grid-tied or grid-connected system, rooftop solar panels installed on a sunny, south-facing roof or panels set up on the ground or a pole mount convert sunlight to direct current (DC) power. An inverter box attached to the home near the electric meter converts the DC power to alternating current (AC) energy to power lights, appliances and other devices. The solar power will feed your home through your service panel. You can purchase and pull power from the electrical utility if the solar panels don’t generate enough power for the home. In many areas, and depending on your agreement with the utility company, when you generate excess solar power, it’ll flow to the utility grid and potentially give you credits against your utility bill. Check to see what’s available in your area.

Federal, state and local incentives can combine to help with the cost of installing a solar power system through rebates and tax credits. Check for specific incentives for your area.

Depending on the size of the system, you can use solar energy to power home appliances, computers and televisions and even to heat and cool your home, reducing your dependence on utilities.

While the value of solar power varies depending on a number of factors, there are some general advantages to using solar power.

• It’s a good option for those interested in sustainable energy.
• You can save on energy bills by reducing your dependence on electrical utilities.
• It’s often considered a home upgrade that can increase your home’s value.
• It typically doesn’t require much maintenance.

However, consider these potential challenges before deciding on a solar energy system.

• The initial installation can be expensive.
• It requires sun exposure that’s not always available for all homes.
• It requires a roof with a surface area and slope that not all homes have.
• The amount of power it generates is dependent on the weather.

Here are five questions to ask yourself about solar energy. If you answer yes to all of them, then solar energy is an option to consider.

1. Do you own your home?
2. If you’re a member of a homeowners association, does the association allow you to install solar panels?
3. Is your average electric bill (not including gas) over $100 a month?
4. Does your home have 300 square feet of sunny, open, south-facing roof space?
5. Do you expect your roof to last for at least five years?

Solar generators use solar panels to collect energy from the sun and store power in a battery. The stored power is available when you plug devices into the generator. Some solar generators can also function as wind generators or collect and store power from a standard household electrical outlet.

In most cases an individual solar generator typically won’t have enough power output to power an entire home, but with the right model, you can power key appliances and devices during a power outage. People primarily use solar generators as temporary or emergency backup power or for power during recreational activities. When sizing an emergency solar generator, be sure to account for the startup and running watts you need. Factor in how long the battery can provide power and how long the generator will take to recharge. Solar generators with high power output and high watt-hour ratings can allow you to power more devices for a longer period of time.

A solar generator can power a small portable or window A/C unit but, depending on the generator, it may not be a practical long-term application. For example, a generator that’s capable of producing 1,800 watts of startup power, 1,400 watts of running power and has a 720-watt-hour capacity could power a small window A/C unit that uses 6,000 British Thermal Units (BTUs), but only for about 45 minutes at most. For longer run times or larger A/C units, you’ll need a generator with higher startup capacity, more running watts and a higher watt-hour rating. You’ll also need enough solar panels to allow the generator to charge efficiently.