PV Solar Panels: PV Solar panels have changed a lot over the past two decades. They used to cost more than $4/per watt. Now they are down to less than $1/watt. They also have higher kilowat output than they used to just a decade ago. There are several different types of solar panels, and there are advocates and critics of the different types.
Inverters: we used to only get/buy/use Xantrex inverters and have been using this brand for more than two decades. However, Xantrex is now part of Snyder electric so we aren't sure of the quality anymore. And, due to various influences, we have been purchasing and using Outback inverters more in the past 15 or so years. So far, Outback seems to be a good product, although their technical support has been less than stellar. We did have to replace the internal workings of one of the Outback inverters a few years ago as a board burned out [possibly due to lightening] but it has been working fine since then.
Update on inverters [Feb 2016]: One of our 3600 Outback inverters 'went out' - we discovered after much time, talking to tech support, and other investigations [MUCH time!] that it was most likely that the transformer on the Outback inverter got messed up [two things 'blow out' the transformer: water and electricity/lightening; we believe it was mouse pee that did it to ours, but that's just a guess]. After MUCH more time, talking to other solar experts, weighing the pros and cons of buying two new inverters [different brand] versus paying to have this one that was no longer working mailed back to Outback Technologies, we decided to do the latter [mail the inverter back to Outback], even though the price for shipping was going to be very high [the inverters weigh about 65 lbs] for two main reasons:
1. there are only two main components to Outback [off-grid] inverters: the boards/electrical circuits and the transformer. We have replaced the boards ourselves, and they don't cost nearly as much as a new inverter. If the transformer goes out, then it is highly likely we would get a refurbished replacement with a 90 day warranty. 2. if we have a problem with the Xantrex [a Schneider company, in Canada], we cannot do anything with it ourselves; it has to be shipped to Canada. We have NO experience with tech support with Schneider; we've had excellent experience with tech support [more recently] from Outback.
Thus, we mailed the 'broken' Outback inverter to the company [in Washington State]. They received it four days later. At the end of the week, we were informed that it was indeed a transformer issue [which we pretty much knew] and that they would mail us a refurbished unit [for free!]. Our Outback inverters are more than 10 years old; we've replaced the boards on one of them ourselves, and now we've replaced the other unit entirely with a refurbished one. Even though the solar company that we deal with alot has said that they see more Outbacks being returned to them, we decided to go with Outback, anyway, because of the two main reasons noted above. We've had very good experiences both with the long-life of the two Outback inverters [the company has said that 10 years is an extraordinarily long time for them to be in good working order], and with tech support. We [at this point] highly recommend Outback inverters. We have heard, however, that Outback is focusing more with 'on-grid' technologies and inverters [we are completely off-the-grid with our electrical system], so we don't know how much longer Outback will carry the boards and replacement refurbished units of the inverters we are using, so that will be a factor down the road. So far, as of 2022, the inverters are still working!
Batteries: We used to use both 6-volt golf cart batteries and L-16 batteries. The deep cycle golf cart batteries supposedly last up about 4 to 5 years, while the L-16 batteries supposedly last about 8 years, although our recent experience has found that not to be the case. We had four L-16 batteries installed in series and we thought that they did not need to be equalized, but recently found out that it may be required to equalize the batteries on a monthly basis to make them last longer. Equalizing the batteries helps prevent build up of sulfation on the plates in the batteries, which may help them last longer (although this is up for debate). So, at this time, we don't know if the L-16s [which cost twice as much as the golf cart batteries] truly do last twice as long as the golf cart batteries. We are going to try an experiment with an electronic desulfinator which supposedly helps them last longer (we could not tell that the battery desulfinator works; it has been taken off). This product is connected to one pole on two different batteries and left on there for the life of the batteries.
Update [Feb 2016] on batteries: we attended a workshop on salt-water batteries; while they have some definite pros, they also have cons. We can report in more detail soon the major pros and cons with them, but at this time, we are not going to switch to salt-water batteries. Battery technology is one of the main weak points for off-grid solar; we are hoping for continuing improvement [and decrease in cost] in batteries in the near future.
Update  on batteries: we replaced our L16 batteries with four...
Lightening arrestors: we have been using the Midnite brand of lightening arrestor, on both the AC and the DC side. According to information we learned, the lightening arrestors we used to use [don't recall the brand] actually didn't work, and after learning more about lightening arrestors from people we trust, we started using the Midnite brand. The lightening arrestors are to prevent electrical surges that occur from lightening that could 'blow out' electronics [although lightening arrestors will not prevent electrical surges from a direct strike, as far as we know].