How to Choose the Best Solar PV System

by Shawn Roe  |  Published in Learn, Solar  |  4 Comments

Occasionally, people ask me how to choose the best solar pv system, or the best panels. Choosing the best solar system depends mainly on your energy needs, roof space, and budget. Most people really want to know how to choose the best solar value. For example, I was asked the following question on my “Help me help you” survey:

I got bid from 2 different installers. One was SunPower panels; the other Canadian Solar. The SunPower bid (for a 5.2 kw DC system) was $21,000 and the Canadian Solar bid was $14,000 – why so far apart?

Solar Roof PosterizedGreat question. There could be many explanations why there is such a gap in the price. Generally, SunPower’s superior efficiency allows for it/ necessitates that it price its solar panels higher. (They have to pay for the best engineers to get the best efficiency, right?) Each installer may be giving you the best deal he can with both brands of panels. What you should check on both proposals is not the DC system size (in this case 5.2 kw DC), but the kilowatt-hours output. Ask your installer(s) how much energy (in kwh) each system expects to produce in the first year.

Then, divide the total cost of the system ($21,000, or $14,000) by the amount of energy produced. This will tell you how much money per kwh you’ll be paying. If money matters (which to most people it does), then choose the solar system with the best VALUE!

Another visitor asked:

Should I be looking for the panel that has the highest efficiency or for the panel that produces electricity at the lowest rate?

If space is a concern, meaning that you have very limited space and want to produce as much energy as possible, then look for the highest efficiency on the Top 40 Most Efficient Solar Panels chart. However, most people will consider price as an important factor. Therefore, for most people, I recommend choosing the panel that produces the most electricity (kwh) at the lowest cost.

Solar Value Comparison Chart

It depends what is most important to you. If saving space is important (rarely the case), then choose the panels that have a smaller area. If saving money, while maximizing output (energy production) is important (usually the case), then choose the solar pv system with the best value.

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Responses

  1. Margaret Collins says:

    March 3rd, 2010 at 9:15 am (#)

    This is great advice: people often have no idea how to go about evaluating bids that on the surface seem quite similar, yet have different price tags.

    One question for you: why do you recommend looking at year-one kWh production as an evaluation tool? Since panels always start off (for the first few months) producing at a higher rate than that which they settle into, wouldn’t a projected average or a year-two number be more reliable?

    Thanks for the thoughtful article.

  2. SRoeCo Solar says:

    March 3rd, 2010 at 10:12 pm (#)

    Glad you liked the article Margaret!

    Sure, any value that takes into account a fuller proportion of the expected lifetime production will likely be more reliable. But as long as you are comparing consistent, accurately verifiable data, (as I have done with the year-one numbers) then the comparison is relevant and valuable. The data used to obtain the year-one kWh production of the theoretical systems above comes from the California State Incentive EPBB calculator which takes into account the most factors I’ve seen to produce a consistent, comparable production prediction. If you know of, or have access to a more robust data set with which I could compare expected production, please contact me.

    Thanks for the comment!

  3. John says:

    October 11th, 2011 at 9:11 am (#)

    Why do you not compare these with Unisolar products?

  4. SRoeCo Solar says:

    October 11th, 2011 at 10:54 pm (#)

    Hello John. I simply chose two common solar modules to illustrate an example. Also, United Solar produces thin-film modules which would require a significantly larger roof space (~950 sqft, or almost twice as much) to produce the same output as these two crystalline modules. *Math: 5.88 kW / 144 W Uni-solar PVL-144 module = 41 modules. 41 modules x 23.25 sqft/module = 953 sqft.

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