Photovoltaic Home Evaluation

[Vic99]

I've got a guy coming out to give me a quote for a PV grid tied system Friday morning (tomorrow). For those of you that know about the process, any issues that you wish that you knew about ahead of time? Anything you wish you had done differently?

Of course I want to know about rebates, size of system, do trees need to be cut (I don't think so), warranty, computer based monitoring.

Thanks.

 

[GaryGary]

Hi,
I'd be very careful about shading.
I'd have him show you in detail how he does the shading analysis.
Remember that shading can come from distant things like trees and buildings and hills, but also from nearby things like dormers, chimneys, and plumbing vents.

Gary

 

[daveswoodhauler]

Hi,
I'd be very careful about shading.
I'd have him show you in detail how he does the shading analysis.
Remember that shading can come from distant things like trees and buildings and hills, but also from nearby things like dormers, chimneys, and plumbing vents.

Gary

Plus 1 on the shading. I have also heard (I'm sure some here can confirm) that even if you have only a little shading on one of the panels, it can have a large impact on the entire array. i.e. Say if you have 16 panels and only a portion of 1 is shaded, it can have a major impact on the output. Let us know how you mkae out.

 

[peakbagger]

Shading is the big issue. They really should get up on the roof rather than project the shading impact from ground level. If the local trees have not leafed out make sure they factor that in. They also should estimate future shading impacts from yours or the neighbors trees. You can trim your trees but its tougher with neighbors trees. Some states have "solar shading laws" but most dont so if there is a chance that someone can build something impacting your shading, you may want to consider this.

You should also ask about code compliance when designing the size of the array as some jurisdictions require a space on the edges and ridge line of the roof for fire department access. If that applies and is not figured in, they may size an array larger than can legally be installed. If there are any vent stacks on the proposed roof area they need to be relocated unless they proposed system uses microinverters (which will isolate the impact of the vent shadow to one panel). In general some shading in the morning and evening during winter at high latitudes occurs frequently, what you really need to make sure is the from about 9 to 3 that there is no shading. Different power utilities have different rules, some require a seperate meter to record output most install a meter capable of two way operation. Some jurisdictions require utility accessible disconnects some dont. They also should check your service entrance size. Most likely not an issue with 200 amp services but if you have an old 60 Amp service that limits the amount of current you can backfeed unless you do an supply side tap. He should ask about you usage over a several year period. Most net metering contracts do not pay you for surplus generation so it rarely makes sense to oversize over your yearly usage. Some net metering deals zero out your account yearly and if so that also impacts the sizing depending on when they zero the account. If the utllity is paying for feed in tariffs then it usually makes sense to go big but again its depending on the utilities rules.

I would ask if the instalation is done with the companies crews or subbed out. Many electrical contractors dont really know solar and it may show in the quality. NABCEP certified installers are the "gold standard", they have to be up to speed on solar and have continuing education requirements. A subcontracted electrcial contractor may not be NABCEP. Obviously check references and go look at some of theri prior installations.

By the way if you dont have a new roof and may need to change it in a few years, get it done before the panels are installed. The salesman may say its easy to move the panels during a roof replacement but if you have to pay someone to do it, there is near double the labor of the original install to remove and replace them and the odds are the salesman is long gone.

In general realize that the individual coming to do the quote may be a "used car salesman" that changed careers and may be working on commission. Most of the estimating software is canned and in about 8 hours they can become a "solar expert". There are a lot of good folks out there but the good ones dont tend to advertise. I would ask right up front politely if he is going to get a commision on the sale as that wiill be an incentive for selling you a large system. Leasing is a whole other story and be very careful if going that way.

 

[Vic99]

Good advice all. Will report back in a day or two.

 

[Slow1]

Probably a bit late for the analysis, but once you get a quote, do consider asking what other options they considered (if any) regarding inverters (central vs micro) and brands. I was disappointed to find out that the company I went with built a system for someone else (who I actually referred them to) using a different brand inverter that actually came with free monitoring whereas mine did not. Otherwise their system was the same cost/watt. Had I thought to ask what other systems they might use and the pros/cons of each I may have made a different decision.

Obviously you will want to get more than one bid on the job anyway. But as other's have already said - shading analysis is critical if you have ANY shading at all. If they don't get on the roof to do it then it is basically a wild guess, even using the best tools of the trade it is essentially an educated estimate, but that is better!