FAQ

Solar panels are made up of photovoltaic (PV) cells made of silicon. When the sun’s rays hit them, these cells convert sunlight to electricity. Individual cells are wired together to form a solar panel. They are coated in tempered glass, which allows them to withstand harsh weather.

The electricity produced by a single solar panel is not enough to power a home or business, so multiple solar panels are needed. The number of panels varies by installation, but every solar system (also called an “array”) will include a series of panels mounted and wired together. This array may be installed on a roof (“rooftop solar”) or on the ground-level (“ground-mounted solar”).

The electricity generated by solar panels takes the form of direct current (DC). However, most appliances and electricity-consuming objects (called “electric load”) require alternating current (AC). To convert the solar electricity from DC to AC, an inverter is needed.

Once electricity is produced by the solar panels and converted from DC to AC by the inverter(s), it will flow through your electric meter and into your home or building. It will be used on site the moment it is created. Any excess will flow back out through your electric meter and onto the local grid.

Photovoltaic panels can use direct or indirect sunlight to generate power, though they are most effective in direct sunlight. Solar panels will still work even when the light is reflected or partially blocked by clouds. Rain actually helps to keep your panels operating efficiently by washing away any dust or dirt. If you live in an area with a strong net metering policy, excess energy generated by your panels during sunny hours will offset energy that you use at night and other times when your system isn’t operating at full capacity.

The size of your optimal solar array will be influenced by many variables. Before analyzing those variables, you should understand how solar is sized and measured. The electrical capacity of solar panels is measured in watts (W). The typical solar panel is rated at 250-300 W. To get the total power (in watts) of your solar array, add together the wattages of each panel. Let’s say you had 10 x 300 W panels installed. The total wattage of your system would equal 3,000 W. 1,000 W is equal to 1 kilowatt (kW), so another way to describe the size of that system would be 3 kW. The average size of a solar array is 5 kW.

Installers will estimate how many panels can fit on your roof given its footprint and shade susceptibility to determine the ideal size of your system. If the size of your roof is limited (meaning fewer panels can be installed), installers can compensate by offering high-efficiency panels. These panels will have a higher power rating (typically 300-350 W), and therefore will produce more electricity per panel. Installers will also use geospatial data to determine the optimal system size for your property, as roof orientation and climate factors will affect how much electricity your system produces. The final factor that will influence the size of your solar array is your project budget. Installers work closely with clients to maximize the amount of solar they install for the customer’s budget.

While sizing your solar array, installers will consider how much the solar electrical output will offset your electricity needs. While the power capacity of solar panels is measured in watts (or kilowatts), the amount of electricity produced by the panels is measured in watt-hours (or kilowatt-hours).

You may recognize the term kilowatt-hour (kWh) from your electric bill. ZESA charges their customers based on how many kWh of electricity they consume each month. If you look at your utility bill from any billing cycle, you’ll be able to see exactly how many kWh of electricity your home or building consumed that month. Each kW of solar you install will produce a certain number of kWh, which will directly offset your utility electricity consumption. The kW-to-kWh relationship varies with latitude and climate. Your installer will be able to accurately predict how many kWh of electricity your solar panels will produce each year.

The size of the battery bank you need depends on several factors and is specific to your needs and to your home. A qualified energy installer should look at the following to determine what you need:

1) What kinds of loads you would like to run while the power is out

Your installer should look at which appliances, lighting, and other loads you want to power in an outage in order to determine how much energy they will use over the time period you want to keep them running. To size your battery system, the installer will add up the required number of watt-hours per electrical load over the desired backup period and the maximum number of watts you’ll need at any given time during a backup period. Bigger loads like electric stoves, electric water heaters and whole-house air conditioners may not be able to be backed up.

2) Suitable space in or outside your home to place batteries

Depending on the type, batteries may need to be located inside or outside. If located outside, and depending on batter chemistry, they may need to be placed in a shaded, temperate area. Your installer might need to adjust the size of your battery system to accommodate your available space.

3) How long the batteries are able to run without being re-charged

A battery system that operates your appliances and lights for one day would be smaller than a system that can operate the same equipment for two days without being re-charged. Your installer will guide you through how long you want to be able to run your appliances, but for most battery backup systems the standard length of run time is one day, especially if you have solar on site to re-charge your batteries.

4) Your budget

Because batteries can be expensive, most people size their systems to only power critical electrical loads while utility service is out. Your installer will help you decide which loads you want to power with your battery given your budgetary constraints.