maino82

The downsides of wiring up long strings of panels in series are ones we run into quite often. The reasons for wiring them up in series are detailed out pretty well in other people's responses, but I thought maybe I'd tackle how we get around some of the issues with wiring in series.

The most obvious problem is that if a series wire gets cut, you lose the entire string. There are companies out there that make microinverters that go on every panel, which help eliminate this problem, albeit at a higher initial cost and additional maintenance.

Shading is also a problem with series wiring. When one panel in a string gets shaded, that string can't maintain the voltage required by the inverter to operate properly, so the inverter just ignores that particular string. Microinverters also help with shading issues, but there are systems out there that mitigate the effect of shading on the arrays that result from the strings being wired in series. Tigo attempts to keep the voltage matched between strings as well as possible so you can keep your inverter operating as long as possible.

It never hurts to double check the calcs yourself if you're investing in a system. Not all salesmen are shady, but I'm sure there are some out there that fudge the numbers. There's some free software out there that's relatively easy to use that you can plug in the data for your location/system and get a good estimate of the production.

Most utilities look at your bill on a yearly basis if you have a PV installation. You generally will produce more energy than you need in the summer, and then less in the winter, so they'll look at your total usage and total production at the end of the year and true everything up.

In general, the cost of energy will likely only go up over time. Unless you anticipate your energy consumption will go up tremendously, you should be in good shape if you install enough PV now to cover all your energy usage.

The panels will last forever, pretty much. They just lose output over time (usually 1/4% to 1/2% per year, although it levels off over time usually). Usually the protective layer is glass. I've never taken a thermal reading of the panels, but there are systems out there that combine solar hot water and PV, so it must get reasonably hot if they're able to get usable hot water out of the system.