Meter

A meter measures kilowatt-hours.

If a meter is connected to an inverter, it will measure the number of kilowatt-hours produced by that inverter.

Typically, meters are wired between the service entrance and the main service panel, and they indicate how much power the house has used.  Utility companies use meters to figure out how much to bill you.

The meter in this picture is a "Net Meter."  Note the red sticker on the bottom right.  Also notice that there is an arrow pointing to the left, underneath the number "4" on the LED screen.  This is indicating that the meter is actually running backwards, counting down the number of kilowatt-hours that the house has consumed.  In effect, Net Metering is a way to get your utility company to buy your clean power.  Many homes do this.

Parts of a PV System

There are only a limited number of components necessary when installing a solar electrical system.  If you understand what those parts are, and what they do, then you can begin to learn how to select parts that work together.  It's simple!

If you feel overwhelmed by the complexity of the world, just remember that you need to learn more about the parts that make the world such a complex, unique place.  The parts are simple, and they have recognizable characteristics.

All you need to build a solar electrical system that is grid-tied and supports your home energy needs!  Right here!

So here they are.  The Solar Panels are just one step in the process of designing a complete solar electrical project.  They run to a "combiner box" which is where electrical parts perform some math duties on the voltage and amperage before heading off to the inverter.

The inverter is where all your AC power is made.  It's wired into your main service panel just like anything else in your home.

Inverter

The inverter converts solar DC current into AC power that your home can use.  It's a central part of an installation, because all solar panels generate DC power, and the grid is AC.  There always must be an inverter.

[Recommended Manufacturers]
[Think Like An Inverter]
[Calculations]

EMT Conduit

DC Solar electricity inside of residences in America are required to be encased in EMT, which is metal conduit.  It becomes a challenge to weave conduit in and out and between many of the commonplace things you encounter in the average home.  A good electrician can work wonders with a piece of EMT, though there are a few simple rules to remember when dealing with it.

You can't exceed 360 degrees in bends, with any pipe run.  In order to "reset" the bends in your pipe run, an electrician can use a "pull point" which can be an "LB" or a J-box of some kind.  Fun stuff.

EMT is necessary inside of homes for solar, because in the event that there is a fire in your home during the day, the idea is that a fireman cutting through a wall with solar current running through it will not get electrocuted (nor you or anyone in the future who decides to do some renovations).

The NEC is designed to prevent fires, primarily, but it also keeps people from getting electrocuted, which is also quite useful.  Make sure that you have a licensed, experienced electrician on site, constructing your PV system's conduit run.

Solar Panel

A solar panel is a modular housing unit, enclosing photovoltaic cells and containing wires to connect power into a solar electrical system.

Panels are rated by their performance in Standard Test Conditions (STC).  STC is the method of determining comparative performance of solar panels fairly.
Included:

VOC open circuit voltage
VMP max. power voltage
ISC short circuit current
IMP max. power current

Main Service Panel

All homes have main service panels.  It is your home's electrical power distribution center.  If any of the circuits in your home are overloaded, this  is where you must go to reset the breaker and get things running again.  Circuit breakers are housed inside of service panels and are designed to prevent circuits from overloading the wires that transfer the electrical energy to the components requesting the energy.

There is a rule for determining if your service panel is sufficient for solar power.  It's a bit complicated, but you can read how much solar your home's electrical system can handle, without any major upgrades, over here. 

Solar electrical systems are wired into the main service panel, just like any other device.  The difference, however, is that the solar electrical system provides power, while most appliances consume energy.  

main service panel, to the left in this photo.

Mounting System

There are a number of different kinds of mounting systems.  These are all listed above.  The panels need to be attached to a structure in some way, shape or form, right?  That's what a mounting system does.  It attaches the panels to the structure they're mounted on. 

Types of Mounting Systems

Roof Mounts

Roof mounts come in a few different forms, but they're all fairly similar.  Most are made out of aluminum and fasten into the rafters of your home, through the shingles.  There are effective ways of getting your roof mount not to leak.  The most effective way of accomplishing this is to use flashings for every lag screw that goes through your roof to support a rail footing.  

For the most part, the average roof mounting system is essentially connected directly to your home without much leverage in your ability to tilt the panels in any particular direction.  You can install tilt mounts on a shingle roof, if you want, and the result can sometimes benefit your annual production.  But most people don't install tilts on their homes, even though it's possible, just because it can look something awful.

Flat Roof Tilted Mounts

Most mounting systems that are designed for flat roofs utilize a counter-ballast system.  Meaning?  Blocks of cement are usually used to keep the mounting systems on the roof in the event of high winds.  The rails are connected to trays which hold the blocks.  

Ground Mounts

If you've ever seen solar panels out in a field, they're ground-mounted.  It's sometimes the same stuff that is used on residential mounts (in fact, all of these rail mounting systems are very similar in the ways that the panels attach).  Ground mounts are connected by pouring cement into cylindrical areas around the footings.

Pole Mounts

Pole mounts are different from ground mounts, in the sense that they can be adjusted easily.  They contain a part called a "mast" which goes to a series of rails that can hold usually 12 or 16 solar panels.  

Some pole mounts are able to track the sun, meaning that motors and sensors make it possible for the array to face the sun at an optimal angle all day.  This can have as much as a 20% improvement on the overall production of the system.  

Research

Unirac Mounting Systems

WattSun Solar Trackers

Disconnect

A disconnect is a device that shuts off all flowing power safely in the event of a service call or emergency.

You will find two in a residential PV system.  One, located between the panel DC wiring and the inverter.  The other, between the main service panel and the inverter.

Sometimes, inverters have built-in disconnects.

Residential power systems rely on the smaller-sized disconnects, which are rated by the amperage they are allowed to handle.  They come in 30 amp and 60 amp versions.

Solar Panel Wiring Box

On the back of every solar panel, there is a housing unit for the blocking diodes where the leads that come from the panels connect to the cells.  Here is an inside look at what that looks like in a Sunpower Panel.  The blue arrows point to the blocking diodes.  The red arrow points to where a wire should be running from, but as you can see, it's been pulled out by an installer who put too much tension on the wire and pulled it from its connection (I'm not naming any names).

The point of showing you this is to explain the difference between a Panel J-Box and the other places you might see the term J-box (junctionbox).  For example, the combiner box could be considered a J-box, but luckily we came up with a neat term for it so you wouldn't get it mixed up.

Combiner Box

A combiner box is a junction box on the DC side of the system.  This is the point where the solar panels are combined, essentially where the system is electrically connected into a fewer number of circuits through parallel wiring.

If this is confusing, maybe it could be explained a little better.  This part of the system requires an understanding of voltage and amperage, but it's fundamental in understanding how panels are wired.  Every system with more than 2 strings require a combiner box, whether it's located at or within the inverter, or higher up near the array.

Benefits Of Combiner Boxes
Many installers use combiner boxes as an opportunity to change the wiring from outdoor-rated USE-2 wire, to the conduit-insulated THHN or similar, which can fit more comfortably in the EMT that is required.  It's also a chance to fuse a system upon entry to a building, which is a smart move, from the perspective of fire safety.

Read More:
Combiner Box Assembly