Will my roof leak?
Your solar installer should be trained in proper roofing methods to prevent the solar mounting hardware from causing roof leaks. If you have a metal roof of the "standing seam" type the hardware can clamp to the seam itself with only piping or conduit penetrations required. If you have a flat roof, as with most commercial property. With PV there are ballasted mounting systems for flat roofs that require no mounting penetrations and will withstand winds up to 90 mph. Ballasted systems are even being introduced in the solar thermal industry.
Will snow be a problem?
Any sloped roof facing South ± 30° will tend to melt once it is exposed to sunlight. Also sunlight actually penetrates snow with enough light striking the thermal collectors to cause them to start working just enough for their waste heat to melt the snow as well.
What about hail?
Will it break the glass over the collectors? They are as resistant as skylights and it is uncommon for skylights to break in a hailstorm. The Sunda brand evacuated glass tubes are rated to withstand hail up to about 1.5" diameter at terminal velocity. Still, we recommend that you declare your solar system with your Homeowner's Liability Insurance policy.
Do photovoltaic panels require any cleaning?
In some areas heavy dust might accumulate as well as bird droppings. Usually it rains often enough that this is not much of an issue. In a prolonged drought you might want to take your garden hose to them with a spray nozzle, but this can be done from the ground. If you have a ground mount and want to get really fastidious about this I guess you could squeegee them as well and wring out every last drop of energy production, but then you would be one rare individual.
What is a solar site analysis?
Every potential location for a solar installation has a solar window. Sometimes that window is partially shaded by trees, mountains, or other buildings some of the time. A solar system designer will come to your home or business and discuss the various solar technologies that would be applicable to your situation and then use various tools to determine the percentage of shading and how much solar energy is available in your solar window. Some of the analysis tools are designed to interface with computer software that automatically calculates the shading factor. This information, coupled with array altitude and azimuth information then makes it possible to determine how much energy can be produced at that particular location. Without this information it is impossible to do a financial analysis and determine the ROI (return on investment).
So how big a deal is shading?
With thermal collectors there is a general rule of thumb that if it is, for example, 10% shaded at any given time, then it is 90% efficient. However, with PV this is not the case. PV panels are wired in series strings. If a series string has any shade at all its efficiency will drop dramatically. The thoroughness, or lack of it, on the part of your solar designer toward shade analysis can profoundly affect the final efficiency of your PV system. There are, however, new technologies that deal with the shading problem. For a modest additional cost they can effectively address the shading problem, but keep in mind that shade is not just a chimney or a vent stack, but snow as well. Snow may slide off most of a roof array, but tend to get trapped on the panels near a roof valley. With grid-tie where one is only concerned with annual energy production snow is not necessarily a major concern because the total amount of time that snow acts as shade really isn't that much time out of a whole year. However, in an off-grid application where maximum energy production in the winter is needed, this can be very important. As for you, the consumer, plant only trees in front of the installation that do not grow tall and eventually shade it, and try to anticipate the worst that a neighbor might do with a new building or tree planting that might cause future shading problems. Colorado law actually has a provision for solar easements.
How can I keep up with rebates, credits, and other incentives?
At www.dsireusa.org click on your state on the national map. This will take you to all federal, state, and local incentives. It is periodically updated, but it still may lag by a few months.
Should I wait for a technology breakthrough?
Solar thermal is a mature technology and nothing significant is anticipated in the forseeable future. With the exception of the aforementioned anti-shading technology much the same could be said of photovoltaics. With PV becoming more mainstream the price has come down dramatically. As for a technology breakthrough in PV the most likely candidate is to increase the light spectrum range utilized by PV modules. Currently the spectrum range is near the infrared end of white light and on into the infrared range. The photovoltaic panels used on space satellites, etc. have efficiencies of converting light into electricity in the 30's% compared to our applications around 16%, but this is because they utilize a wider frequency band and cost is no object. There is ongoing R&D to make this technology affordable, but there are no indications it will be anytime soon.
Sometimes you see solar collectors or PV panels racked up where they are not set parallel to the roof slope. Is this really necessary? The ideal year round angle to the horizon is the geographical lattitude of your location. This is about 37° here in the Four Corners region and is the equivalent of a steep 9:12 roof pitch. With PV the inefficiencies of not racking to lattitude are usually inconsequential. With solar thermal collectors it is more significant, but aesthetics matter as well. Perhaps an additional collector will make up the difference and they can all lay parallel with a lesser pitched roof, and, of course, a pole or ground mount can be set to the ideal angle. With radiant space heating the ideal angle is going to be lattitude plus 15° because the sun is lower in the winter sky. This is 52° for our region, another reason to consider a ground mount for maximum radiant space heating efficiency.
Can my homeowner's association prevent me from installing solar on my property?
Actually Colorado and New Mexico have laws prohibiting HOA's from doing this. In Colorado HOA's can have a say as to the appearance or aesthetics of the installation, but not to the point where it would cause a major increase in the cost.