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SolarTown Learning

Choosing Your Solar Panels: More than Meets the Eye

02-15-2010
Category: Solar Panels

SolarTown's Comparison of Several Leading Solar Panels

Many homeowners leave the choice of their solar modules or solar panels to their installers. While this is an easy route for them to take, they would not leave their choice of kitchen appliances solely to their plumbers. They would not leave the choice of their plants to their gardeners. Homeowners should look to these professionals for suggestions, but of course they should not rely solely on someone else to make these major decisions. We suggest not leaving the choice of solar modules solely to your installer either.

Many installers do not know the many differences among solar panels for the home. Many times they have a preferred relationship with a distributor or manufacturer and the installers can maximize their markup by using a particular solar panel. This relationship can influence the installer's choice of which panel to install. That does not make for an unbiased opinion on which solar panel you should have on your roof for the next 25-30 years.

There are many factors that may influence your decision. It is more than a choice of price versus quality. As a starting point, we recommend that you read SolarTown's Consumer Guide to Buying Solar Panels. To illustrate some of the factors that may affect your decision, we have taken some of the panels SolarTown carries and analyzed the specifications for them. You have to decide what factors are important to you, and knowing this, your choice of panels may change.

These are panels that we compared.

We compared the specifications of these solar modules, using various metrics. We used the PTC (PVUsa Test Conditions) rating, the size of the panels, and the cost of the panels. We have not used other important factors such as efficiency, length of warranty, and the expected degradation of the panels from year to year. You should also compare the negative tolerance ratings given by the manufacturers, which some use as a proxy for solar panel quality. And aesthetics, how the home solar panels look on your roof, are also important. You will want to consider these factors as well when choosing your solar panels.

PTC Rating

As you may recall from reading the Solar Panels Consumer Guide, the PTC rating is an independent rating of the solar panels. In general, the PTC rating is about 90% of the nameplate rating, the rating that is advertised on the panel. For example, the name plate rating of the Sharp 230 is 230, but the PTC rating is 198, or 86% of the name plate rating. As shown in the chart, the Sanyo PTC rating is 93% of the nameplate rating for the Sanyo 210. Contrast that to the Sharp and GE solar panels, for which the PTC rating is 86%.

 

Sanyo 210

Sharp 230

BP 200

Canadian Solar 230e

GE Solar 200W

Solon Blue 220W

PTC Rating

195

198

177.6

209.4

173

194.3

PTC/Nameplate

93%

86%

89%

91%

87%

88%

  

Size Matters

Let's assume that you have size limitations on your roof-most of us do. We have used as a baseline a 500 square foot roof, which we assume is a square 22.3 feet by 22.3 feet. As part of this model installation, we assume that you do not want your panels hanging off the side of the roof. How many panels from our select group can you fit onto your roof? These are the results.

Sanyo 210

Sharp 230

BP 200

Canadian Solar 230e

GE Solar 200W

Solon Blue 220W

# of panels

500 sq ft

32

24

32

28

28

24

Array Watts (Name Plate)

6720

5520

6400

6440

5600

5280

Array PTC Watts (Actual)

6240

 4752

 5683

5863

4844

4663

Expected Annual Output Daily year avg 4.47)

10,183

7752

9271

8084

7902

7606

The size of your array will differ considerably depending on which panels you use. You can fit more of the Sanyo and BP solar panels than the other panels. You can fit only 24 of the Sharp or Solon Blue panels on your roof, but you can fit 32 of the BP 200 or Sanyo 210. What that means is that if you purchase the Solon Blue panels, you would get only a 5.3 kW array, but if you choose the Sanyo solar panels, you would get a 6.7 kW array. And you would have a 6.4 kW array with the BP and Canadian Solar panels.

Size and PTC Rating Combined

If you factor in the PTC rating, your array could range from a high of 6.2 kW for the Sanyo 210 panels, to a low of 4.6 kW for the Solon Blue 220W solar panels. And take a look at what the difference will be in terms of expected annual output. Because you will not be able to get that many panels on your roof with the Sharp and the Solon, the expected annual output is nearly 25% less than the Sanyo panels. That's a huge difference. And you want your installer to make this decision for you? You need to take your solar fate into your own hands.

Price of the Solar Module

You are still not convinced how important it is for you to participate in the decision of which solar modules should grace your roof for the next 2 to 3 decades? You are of course right that the Sanyo solar panels will cost you more. If we use the cost of these products from the SolarTown Solar Energy Store, you can see that the cost will significantly differ depending on your choice. We have used the current retail price of these home solar power panels in the SolarTown store-which of course do not include installation costs. (And remember if you purchase these panels in quantity, we would be happy to give you a discount. But for our purposes, we are using the current list prices on SolarTown.com.)

As you can see from the chart below, the panel cost for your array will differ considerably. The Solon Blue array on your 500 sq ft roof will only cost about $16,000 while the Sanyo array will cost over $27,000, or 69% more.

 

Sanyo 210

Sharp 230

BP 200

Canadian Solar 230e

GE Solar 200W

Solon Blue 220W

Cost Per Panel

$849

$715

$879

$633

$880

$664

Cost for Array

$27,168

$17,160

$28,128

$17,724

$24,640

$15,936

Cost Per Watt (PTC output)

$4.35

$3.61

$4.95

$3.02

$5.09

$3.42

  

Cost per Watt

Cost may and probably is an important factor as you look at this selection of home solar power panels. We have tried to equalize all of these factors by showing the cost per watt based on the PTC output rating. The most expensive of this assortment of solar panels were the BP 200 solar panels and the GE Solar 200 solar panels. The least expensive solar panels based on this metric were the Canadian Solar, Solon Blue and the Sharp 230.

That doesn't mean you should run out and purchase one of these home solar power panels. It depends on what your goal is. If it is to have the most output based on roof size, then the Sanyo solar panels may be the right selection for you. If you factor cost into the equation, then the Canadian Solar panels looks like a good choice.

5kW System or Bust

Now let's say that you do not have any size constraints on your roof. You are mostly interested in getting a 5 kW system on your roof. To make this a fair game, we will use the PTC rating.

 

Sanyo 210

Sharp 230

BP 200

Canadian Solar 230e

GE Solar 200W

Solon Blue 220W

# of Panels

26

26

29

24

29

26

Maximum Output (Watts)

5070

5148

5150

5026

5017

5051

Expected Annual Output (Daily year avg 4.47)

8271

8399

8403

8200

8185

8242

Cost for Array

$22,074

$18,590

$25,491

$15,192

$25,520

$17,264

As shown in the chart, you would need only 24 of the Canadian Solar 230e panels but 29 of the BP 200 panels to build a 5 kW array on your roof. The equipment cost for your solar array will differ significantly. To get your 5 kW Canadian Solar array, it will cost just over $15,000, but your BP solar array will cost over $25,000, 67% more.

Each homeowner faces various constraints when choosing solar panels. It is not a decision that you should take lightly as you will be living with these solar panels on your roof for a long time to come. The key factors that will influence your decision may and will differ from homeowner to homeowner. Once you have the tools to compare the various options on these solar panels, we hope that your decision will be easier to make.

Related Article: Solar Module Comparison

Tags: Sanyo solar panels, Sharp solar panels, BP solar panels, Canadian Solar panels, GE Solar solar panels, Solon Blue solar panels, solar panels, solar modules, PTC rating, solar panel sizes, cost per watt, solar panel prices, solar panel costs, solar module output, discount solar panels, solar panel comparison, solar panel reviews, solar home panel 


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