Questions about solar? Get the answers here.

Questions about solar? Over the years, we have compiled our customers’ most frequently asked questions (FAQs) about solar. The perfect place to get started for unbiased information so you can make the best decision.

How many solar panels and what size are enough to meet my power need requirements?

Each energy consumer has different needs, dependent upon the electric appliances being run. For instance, if you are powering two 27 watt compact fluorescent light bulbs for two hours, you would need to supply 108 watt-hours of energy (2x 27x 2 hours). In San Diego, which has a yearly average insolation of 5 hours a day, one 32 watt photo voltaic (PV) module is more than adequate (32x 5 hours=160 watt-hours).

To find out how much energy you use, contact us, we would love to help you.

 

What if there is hardly any sunshine for several days?

Most solar electric systems today are connected to the utility lines - allowing you to send energy back to utility grid turning the meter backwards, or using power from the utility at times when there is no sunshine including when its dark outside. This connection to the utility grid ensures you will always have power to your home or business.

Different geographic areas provide different amounts of daily sunshine. For instance, the American Southwest averages 5 sunshine hours per day and the Northeast receives about 3 hours of daily sunshine. More solar panels will increase the amount of power generated when the sun is shining. Solar Electric sizes each system based on your area and also takes into account, shading from trees and other obstructions on your roof or surrounding area for optimal year-round performance.

How long do solar panels normally last?

New solar panels have a manufacturer's warranty of 20 years. With proper care, however, the panels should last many years beyond the warranty. You can expect your solar modules to continue to produce power for 60 years or more.

What maintenance is required for a solar electric system?

Solar electric systems are elegantly simple. Maintenance includes:

• Occasional checks of the connections between the solar modules and the inverter(s), and to tighten them when applicable.

Do some solar panels generate more power per inch than others?

Some solar panels do generate more power per inch than others. For example,

• Monocrystalline panels have a higher output per square foot than amorphous silicon panels. Traditionally, if square footage was important, monocrystalline solar modules were the best choice due to a higher conversion rate of sunlight to electricity.
• New amorphous silicon panels <link to UniSolar panels in the store> absorb three different spectral wavelengths, which translates to up to 30% more real power per watt from the PV module. This is because the amorphous panels produce energy for longer periods each day than monocrystalline panels. This means the panels produce more amp-hours per amp than other technologies.

New and future hybrid designs employ the best of both technologies
 

How can I find out how many watts my appliances use, such as computers and stereo etc.?

There are a few ways to determine how much energy your household appliances use including the following:

• The easiest way is to look at a monthly utility bill. This has the amount of kilowatt-hours consumed during the billed month. From there, a consumer can determine how many average kilowatt-hours were used daily.
• Additionally, a typical electronic appliance should have an energy rating sticker somewhere on the product.
• There are devices available including the Kill-A-Watt that can be used to determine the energy usage of a specific appliance.

How long does it take for a solar system to pay for itself?

The payback period for a solar system is roughly 5-7 years, based on calculations assuming the cost of energy obtained from the utility grid is 10 cents a kilowatt-hour.

What is the difference between a Solar Lease and A PPA (Power Purchase Agreeement)?

While the terms “solar leases” and “solar PPAs” are generally used interchangeably, there are subtle differences between the two. Monthly payments for both options are likely to be very similar. Both options can save you money over what you pay your utility and both options will protect you against rising electricity costs.

With a solar lease, you agree either to pay a monthly “rent” or lease payment in exchange for the right to use all of the power produced by the system.

A solar power purchase agreement (PPA) is similar to a solar lease but differs in one key way. Instead of "renting" the system and receiving the benefits of using it, you instead agree to buy the power generated by the system at a set price per kWh.

Is the current technology more advanced than a few years ago?

The technology behind PV solar energy is continuously improving. Research on thin film materials, processes and devices are leading to increased module efficiencies while using high-throughput, lower-cost plasma processing. Increased module efficiencies coupled with fast deposition rate technologies implies the cost of PV modules will continue to decline.

Do current trends show that solar electricity will become increasingly affordable?

Thin-film modules are less-expensive to manufacture because the amount of materials, capital investment and labor are decreased. According to the US Department of Energy's Fiscal Year 1998 Photovoltaic Energy Program Overview, researchers predict that by optimizing processes and using materials more efficiently, the cost of thin-film manufacturing could drop to $50 a square meter

Why choose solar over wind- or water-power generation?

Every energy source has its advantages and disadvantages. Wind- and water-power generation may be appropriate in certain situations. However, these technologies are

• Limited by seasonal variations
• Have moving parts that require maintenance
• Generate noise
• May negatively affect wildlife

PV modules, on the other hand, are:

• Silent
• Have no moving parts
• Non-glass panels are covered by a 20-year warranty.

Should I use a sine-wave or modified sine-wave inverter?

A modified sine-wave inverter is appropriate for most stand-alone household applications. However, for certain technical appliances or for grid-integrated PV systems, a central sine-wave inverter or micro-inverter is necessary. In grid-integrated systems, energy can be bought and sold to the utility company by the end user.

What is the difference between a micro-inverter and a central inverter?

Micro-inverter. A micro-inverter consists of a small box located on the back of or situated very close to a solar panel. Its role is to convert the DC electricity produced by a single solar panel. Features of a micro inverter:

• Ability to use different makes/models of modules in one system, particularly when repairing or updating older systems
• No need to calculate string lengths – simpler to design systems
• Increased yield from sites that suffer from overshadowing, as one shadowed module doesn’t drag down a whole string
• Allows for increased design flexibility, modules can be installed facing different directions - east, west or south - making the most use of your roof space.
• Lower DC voltage. No need for ~ 600 V DC cabling requiring conduits
• Panel level monitoring
• Parallel operation - in rare instances of failure, that single  panel will not produce panel while the remaining panels will continue to produce electricity.
• Panel level MPPT (Maximum Power Point Tracking)

String inverters. A string inverter is the type most commonly used in home and commercial solar power systems. It is a box that is often placed  near your electric panel. Depending on the size of the installation, there may be more than one string inverter present. String inverter advantages:

• Remote system monitoring capabilities
• Low cost
• 3 phase variations available
• Robust
• High efficiency
• Allows for high design flexibility

Central inverters. Central inverters are designed for large-scale commercial, industrial, government and field applications – Basically, they are a very large string inverter.

What is the difference between a parallel AC system and a series DC system?

The simplest way to think about series vs. parallel systems is thinking about a string of Christmas lights - when one bulb went out, the whole string went out. That is a series system. When one solar panel is shaded, a panel or inverter malfunctions - the entire string goes down. On the other hand, with a  parallel system, when that bulb goes out, that single bulb is the only one out and the rest of the string continues to work.

Series-wired systems are governed by the principles of voltage. A solar array must provide a high enough voltage to enable its inverter to operate at an efficient level and all series-architected solar installations conform to an exact footprint used for the entire array. Best suited for large rooftop and field installations where all the modules are at a the same angle, facing the same direction and in the same location. Parallel-wired systems are not limited by voltage principles or footprint restrictions are best suited for more complicated installations.

What is the difference between EnPhase Micro-inverters and SolarEdge Power Optimizers?

Both are micro-inverters that offer up to 25% increase in the amount of energy they are able to harvest. SolarEdge has a higher 98.3 peak, 97.5% CEC inverter efficiency. Both offer individual solar module monitoring via the Internet on your smart phone or computer.

• Power Rating. EnPhase is rated at 250 watts while Solar Edge offers a power rating  up to 300 watts, ensuring that no power is wasted with larger solar modules.

• Electrolytic Capacitors. SolarEdge does not use any electrolytic capacitors in their under module mounted power optimizers.

• String System. A disadvantage of Solar Edge inverters is that they are string inverters, which means if one fails - the entire string  fails - much like the old Christmas lights where if one bulb went out, none of the lights work.

Are prepackaged ready to go systems available?

PV systems are increasingly being designed for ease-of-use. Prepackaged turnkey (plug-and-play) solar systems are available, and can be custom-designed by Solar Electric fora variety of power projects.

What are the benefits of a micro-inverter?

The homeowners who are more affected by shading are also those that can benefit the most from micro-inverters. Micro-inverters are also excellent for difficult roof orientations - including those installations where panels facing different directions of east, south or west, starter systems and small applications.

• Individual Optimization
• Maximum Power Point Tracking (MPPT)
• Longer Warranty
• Easily Expandable
• Performance Reports
• No Single Point of Failure
• Improved Safety
• Silent

Home + Corporate Energy Storage Systems

Frequently asked questions about battery systems

What voltage should I consider using 12, 24, or 48 Volts?

Solar systems can be sized in 12, 24 or 48 volts. As a general rule, smaller PV systems are run on 12 volts. 24 or 48 volt equipment can handle 4,000 watt systems. 48 volt systems are designed for energy consumption needs of over 4,000 watts. Higher voltage systems use smaller wiring.

What is the best way to monitor the charge status of a solar system?

Battery volt meters are the most common way to monitor the charge status of a solar system. However, battery voltage readings can be inflated depending on charge and discharge rates. For this reason, an amp-hour meter is the most accurate way to monitor the system charge status.
 

What special considerations should be observed where the batteries are placed?

Ideally, storage batteries would be placed in cool, dry and vented locations (batteries release hydrogen gas).  Sheds or garages are good places. The contents of batteries should not be subjected to boiling or freezing. Freezing will only occur when the batteries are in a state of discharge.

How long do solar panels and batteries normally last?

Batteries normally last - with basic routine maintenance and discharge rates of no more than 10 -20% - means your batteries should function effectively for 10 years or more.

What if there is hardly any sunshine for several days?

When solar modules are used to charge a battery bank for energy storage systems, the amount of power stored differs from system to system. This difference is because different geographic areas provide different amounts of daily sunshine. It is recommended that a system has enough battery power to account for five days of inclement weather. The American southwest averages 5 sunshine hours per day and the northeast receives about 3 hours of daily sunshine. More solar panels will increase the amount of power generated when the sun is shining.

What maintenance is required?

Solar electric systems are elegantly simple. Maintenance includes:

• Deep Cycle Batteries. Checking your deep cycle batteries every few weeks to make sure they have enough distilled water. We recommend the use of battery hydrogen caps which reduce the amount of battery maintenance required.
• AGM Batteries. AGM batteries are maintenance- and worry-free, making them a great option for home and business use.
• Solar System. Occasional checks of the connections between the solar modules and the inverter(s), and to tighten them when applicable.

Are prepackaged ready to go systems available?

PV systems are increasingly being designed for ease-of-use. Prepackaged turnkey (plug-and-play) solar systems are available, and can be custom-designed by Solar Electric for a number of power needs requirements.