OK, so you know that your roof is situated for solar exposure and either your utility company offers a rebate or you plan to sell your SREC’s on the open market. Great! Now we can dig into the actual components of a rooftop PV system.
*Disclaimer: You should know that I am not an engineer or electrician so my descriptions are meant for the beginner level. A more detailed definition of solar panel system components can be found here.
Solar Panels –
Our primary criteria when choosing solar panels was finding the panel with the greatest wattage that would fit in our available space. The width and length of our roof allowed for only 2 rows and an exhaust vent protruding from the roof limited us to only 11 panels per row. Therefore, we chose the cheapest panel that met our height and width limits.
We purchased BP Solar 215 watt panels through The Solar BiZ and were extremely happy with the customer service and prices.
Inverter – This is potentially the second most expensive component of your system. The inverter converts the electricity generated by the solar panels (D/C or Direct Current) into usable energy (A/C or Alternating Current).
We chose a single SunnyBoy 7000 inverter in the 7 kW project and Enphase micro-inverters in the 3.5 kW project. Both types of inverter have merit. A single (or string) inverter handles the D/C to A/C conversions for all your panels combined while a micro-inverter needs to be installed on each and every panel to do the same function. The Sunny Boy website has a great tool for determining what size inverter your system would require.
A single inverter has the benefit of only needing to install one per project but it does not allow the monitoring that the micro-inverters offer. Micro-inverters are able to report individual statistics for each panel’s performance while the single inverter can only report on total system production. This could be helpful in identifying which panel is malfunctioning if your system is not working or under-performing. In addition, using micro-inverters makes adding on additional panels at a later time easier.
Mounting Hardware – The mounting hardware supports the PV panels and secures them to your roof. It includes posts or standoffs that are attached to your roof beams as well as rails that hold the panels and keep them secured to the standoffs.
For both of our projects, we chose Iron Ridge mounting hardware because their online tool made it simple for us to estimate the necessary materials and hardware as well as quantities for our specific project. The tool spits out a quote* and material list!
*Note that the quote is priced at MSRP while the individual parts can be found at discounted prices online at other suppliers. We ended up purchasing the Iron Ridge Hardware from PV Power.
After the three main components, there will be other costs such as permit fees, wiring supplies, electrical conduit, AC/DC Disconnect and labor for installation if you do not do the install yourself. Our detailed system costs are outlined here:
That’s it! That’s all it takes to build an entire power plant on your roof! And remember, the costs detailed above are 2010 prices before any rebates or incentives. The same system installed today would likely cost half as much as shown in the examples using 2013 prices in this post.
What about a battery?
Our system is grid-tied, meaning we are connected to the local utility and purchase electricity from them whenever we are not generating power. Our agreement benefits us though in that the utility company buys back any excess power that we generate which is sent back to the grid. Therefore, we don’t need a battery backup at this time.