Featured Solar Products

Solar panels are at the heart of every solar power (PV) system. Typically made primarily of silicon, solar panels make use of the photovoltaic effect (not to be confused with the photoelectric effect, the quantum theory of which led to Albert Einstein's only Nobel Prize) to convert the energy from sunlight into DC electricity, much like that produced by a battery. Unlike a battery, however, solar panels can perform indefinitely and most are guaranteed to produce at least 80% of their nameplate power after 20 or 25 years. Indeed, with no moving parts and no chemical process involved, a solar panel purchased today might outlast us all!

The National Renewable Energy Laboratory in Golden Colorado has a tremendous amount of information about How a Solar Panel Works and other renewable energy issue on their website.

Not all Solar Panels are Created Equal!

From a more practical perspective,to qualify for rebates from electrical utilities every solar panel sold in California must be listed on the approved equipment list produced by the California Energy Commission. Of particular interest on this list is the PTC rating of the different solar panels. The PTC rating is the CEC's estimate of the "real world" power production of a given solar panel. As a result, the PTC rating provides the consumer with one means to compare the performance of two seemingly identical solar panels.

Here's an example - suppose you wanted to compare a Sanyo 200 Watt solar panel with one offered by our competition, say a Sharp 200 Watt panel. How would they compare? The PTC rating for the Sanyo 200 Watt panel is 185.4 Watts (92.7% of nameplate rating) while the Sharp 200 Watt panel is only rated at 173 Watts (86.5% of nameplate). That means that each Sanyo 200Watt panel is likely to produce 12.4 Watts of more power than the corresponding Sharp product. Multiply that difference by the number of panels in your array, and in a typical installation it is like you are getting a couple of extra panels worth of power for free!

Sanyo HIT Power N Module.

For residential solar power systems we feature Sanyo solar panels – the best performing solar panels in the marketplace (Sanyo HIT Power N module shown). Sanyo solar panels have some of the highest efficiency values available (that is, what percentage of the Sun's power does the panel convert into electricity). They consistently out-score the competition when it comes to PTC ratings (as described on the About Solar Panels tab) and they also excel in high temperature performance, as can be seen in this graph:

During the course of the day, as the solar panel heats up, the Sanyo panel (shown in red) produces more power than does a conventional silicon panel (shown in blue). At the middle of the day - when you want your system to be producing the maximum amount of power, the Sanyo panel produces as much as 10% more power than the competition.

That added power is a benefit that you will enjoy every day for the next 25 years - long after the extra cost has been paid back.

Taken together, these many benefits demonstrate why we believe that the Sanyo solar panel is the best product in the market place for residential systems.

Some residential installations require a more cost-effective solar panel solution. To meet that need we are excited to be offering the new Conergy P-series of solar panels. Conergy is the world's largest distributor of solar power products - and these new panels are built to Conergy's demanding specifications in China, providing substantially lower cost without sacrificing quality. In particular, the P-series solar panels have a 90% power output warranty after 12 years and an 80% output power warranty after 25 years.

The addition of these panels to the Run on Sun line of products allows us to offer lower-cost systems where space and shading constraints permit. Combined with our long-standing reliance on SMA inverters, these new panels will allow us to provide high quality but much lower priced systems that will help make solar more affordable than ever before.

When we meet with you, we will explain the pros and cons of the different solar panel options so that you can make the choice that best fits your needs and your budget.

For larger installations, and particularly for commercial systems, we prefer to use solar panels made by Suntech, the largest solar panel manufacturer in China.

Unlike some solar panel manufacturers that are simply interested in building the cheapest product, Suntech has a significant Research & Development effort that allows it to sell panels with a positive power output tolerance which means that the panels will meet or exceed their nameplate ratings. (Compare that to panel manufacturers that have ±5% tolerance ratings which means that your 200 Watt panel might only deliver 190 Watts.)

Suntech panels also have one of the highest output power warranties in the industry: 95% after 5 years, 90% after 12 years, 85% after 18 years and 80% after 25 years. For commercial installations, this means high performance for the lifetime of the installation (or PPA).

Inverters are sophisticated electronic devices that take the DC power produced by the array of solar panels and converts that into AC power that you can connect to a service panel to power your loads. However, modern inverters must do other things as well. Of greatest importance is the ability to constantly monitor the electrical grid for faults. If the grid fails, the inverter must disconnect itself from the grid and remain off until the grid returns to operation and remains stable for five minutes. This feature - known as anti-islanding - is an important safety feature to protect utility workers from shocks.

Historically, there were two types of inverters: so-called "string" inverters that were used for residential systems and their larger cousins, central inverters that were used in larger commercial systems. More recently, an addition to the inverter market has been introduced - the "micro-inverter" which offers great promise for solar sites that suffer from partial shade during the day.

String Inverters

String inverters are the most common inverter products in the marketplace. A string inverter, as the name suggests, operates by wiring a series of solar panels into a string. One or more strings of identical numbers and types of solar panels are then brought back to the inverter for inversion and monitoring. Modern string inverters are highly reliable and come with a ten-year warranty.

Micro-Inverters

The greatest downfall of string inverters is the problem of partial shading of the array. (No device can solve the problem of total shade - for a solar system to be viable it must be largely unshaded.) Partial shading, say from a specific tree or power poll, can have a disproportionate impact on the performance of a solar power system. When a panel gets shaded, it ceases to produce power and adversely affects the performance of the entire string. If there are multiple strings coming back to the inverter, and just one panel from each string is shaded, the entire array could be effectively shut down.

Enphase Micro-Inverter Array with Shading

Micro-inverters do away with strings and each solar panel has its own, much smaller inverter mounted beneath it. As a result, every panel in the array operates independently. If one panel is shaded, the unshaded panels adjacent to it continue to operate without interference. An additional benefit of a micro-inverter system is the ability to monitor in realtime the performance of each individual solar panel.

The illustration here is from an actual system installed by Run on Sun. This is a subset of the entire array and shows a true geographical representation of the array with North at the top of the image. This snapshot was taken at 9:50 in the morning. To the East is a stand of very tall trees. As the sun rises higher in the sky, the shadow line from those trees sweeps across the array. Thus, the panels to the West get full illumination earlier, while panels to the East are still deep in shadow. If this array subset constituted one string, the effective power of the entire string would be negligible. Instead, this subset is producing over 700 Watts - while half the string is still in shade!

Central Inverters

For commercial installations, the most common approach is to use a large, central inverter. These devices are usually free standing and can handle anywhere from 30kW to 1MW or more. Recently some manufacturers, notably Satcon, have taken a page from the micro-inverter design book and have pushed some of the power control circuitry out of the central inverter and into combiner boxes that harmonize the voltage being delivered back to the central inverter.

SMA string inverter

Where site characteristics support them, we feature SMA string inverters, the best selling, most reliable string inverters in the world.  Known as the Sunny Boy, SMA offers a complete line of residential string inverters from 700 to 8,000 Watts.

Not as well known, but SMA also offers a complete monitoring solution and we have installed a couple of systems that use SMA's "webbox" to capture and report performance data from the system. You can see the output from one of those systems here.

Enphase micro-inverter

Enphase micro-inverters offer cutting-edge performance, making solar power installations feasible for residential installations where shading problems would render conventional string inverters ineffective.

We have installed a number of Enphase micro-inverter systems and have closely monitored them to see if we could quantify the improvement in energy yield. Our analysis shows that compared to the energy output predicted by the CSI EPBB calculator, our micro-inverter systems are producing on average 16.7% more energy than predicted.

You can see the realtime performance of one of our Enphase micro-inverter systems by clicking here.

Satcon Solstice Central Inverter

Central inverters are cost-effective solutions to the problem of converting a great deal of DC power into more useful AC. However, central inverters for large solar power systems also constitute a single point of failure that can cause the entire system to fail. In a commercial or PPA environment, such a failure can be costly. Systems with central inverters require routine maintenance as a way of ensuring the maximum percentage of runtime.

One newer product has really caught our eye - the Satcon Solstice. This innovative design pushes some of the energy management/conditioning features of the central inverter out into the field - to a series of specially designed string combiners (the smaller boxes in the photo). These combiners perform a DC-to-DC conversion that guarantees that every string coming back to the inverter is operating at exactly the same DC voltage. This allows the design of the central inverter itself to be optimized for that target voltage.

All solar power systems require a mounting system to support the solar panels. Solar power mounting systems come in a variety of forms depending upon where the array is to be mounted.

Stand-off Roof Mounting Systems

By far the most common mounting system is the stand-off attachment system, such as those manufactured by Unirac. In a stand-off system, a series of metal posts - or stand-offs - are lag bolted into the rafters that support the roof. Those stand-offs are then flashed to make the system water-tight. When done properly, stand-off systems are extremely secure, reliable and provide for excellent system performance since the stand-offs provide clearance from the roof reducing the accumulation of debris and improving airflow which helps cool the array.

Flat-Roof Mounting Systems - Ballasted Arrays

On flat roofs such as what are commonly found on commercial buildings, the multiple attachments used for a stand-off mounting system are disfavored since the possibility of water pooling under the array increases the possibility of leakage. A popular alternative for flat roofs is the ballasted array. In a ballasted array, weight is used to hold the panels in place and resist wind-driven uploads. In Southern California, ballast alone is not sufficient and some attachments are needed for seismic security.

Ground Mounted Systems

Google Solar Carport

For very large arrays, a ground mounting system is required. These systems typically call for the placement of some type of foundation - concrete feet or piers - and then a lattice work of supports.

One increasingly popular variation on this approach is the solar carport such as this one at Google in Mountain View, California. These free-standing structures both provide shade for parking and generate energy - energy which could be used to recharge Electric Vehicles.

Tracking Systems

The final mounting mechanism are tracking systems - ground mounted arrays that follow the sun. Trackers come in two general classes - single axis and dual axis. In addition, trackers can be either passive or powered.

A single-axis tracker follows the movement of the sun as it tracks from East to West each day. Since the system is always pointed in the direction of the sun, energy yields are improved by as much as 25%. However, since the tilt of the array is fixed (usually at latitude), the North-South orientation is a compromise.

A dual-axis tracker overcomes that compromise by also tracking seasonally for North-South variations in the sun's arc. A properly installed and maintained dual-axis tracker can achieve as much as a 40% improvement in energy yield over a conventional ground mounted array, particularly in more northern latitudes where the seasonal variation is more extreme.

However, those performance improvements come at a price - trackers are more expensive to install and need regular maintenance to keep them operating properly.

UNIRAC - Roof and Ground Mount Systems

For roof and ground mounted systems we use mounting solutions from Unirac, the leading manufacturer of solar power mounting systems in the United States.

Stand-off Roof Mounting Systems

6" Standoff with Flashing

Unirac has a variety of stand-off mounting solutions, and we particularly like their Clicksys system for residential pitched roofs. At Run on Sun we start with a 6" aluminum standoff that features two stainless steel lag bolts. This design is twice as secure as the single-bolt designs used by some of our competitors.

As you can see in the photo at right, we then use an aluminum flashing with a UV-resistant rubber boot to seal around the attachment. This approach provides better weather resistance than simple "L-feet" with sealants.

Using the Clicksys system, rails for mounting the panels snap into specially designed clips that bolt onto the top of the standoffs, as you can see in this photo of a Run on Sun installation featured on the Unirac website.

Ballasted Systems

RapidRac Array - Note Ballast Blocks

Unirac's ballasted mounting system is known as RapidRac and it is ideal for commercial flat roofs. The RapidRac system consists of interconnected trays that hold concrete ballast blocks to anchor the array to the roof. Fixed tilt arms connect to the trays to support the solar panels at a pitch of 10 degrees. This provides a good trade-off between energy yield and array density.

To provide seismic security, a special attachment device, called a RapidFoot, is used to prevent lateral movement of the array in the event of an earthquake. The RapidFoot has its own flashing system designed to prevent leakage, and it also lowers the overall ballast needs of the array.

Ground Mount Systems

For fixed-pitch ground mounted systems, Unirac offers U-LA - it's large array solution. U-LA is a modular system that starts at 3kW and can grow to sizes that are only constrained by the available acreage for the array.

Zomeworks tracking system

For tracking systems we like Zomeworks for their elegantly designed passive tracker.