Choosing Solar Panel Wattage - Why Higher Wattage is Rarely Better

Project Solar Blog Icon

Solar companies love to tout their superior equipment. It's one of the primary sales tactics used by the door knocker mafia. There are 3 primary components in a grid tie solar build. 

  1. Racking
  2. Inverters/micro-inverters
  3. Panels

These 3 primary components have a wide range of quality, and it IS important to equip your home with the right equipment. 

In this article, we are going to focus on component #3, the panels (or PV module as they are commonly referred to in the solar industry). 

At Project Solar, we've established relationships with the worlds leading solar panel manufacturers. The same manufacturers that all the big national installers use, like Jinko, Silfab, LG, Canadian Solar, etc. 

Through these relationships, we are able to get volume discounts, making our product and service cheaper than if you were to source yourself. 


Differences in Panels

Not all panels are created equal. Panels vary in a variety of ways, namely in  technology used, aesthetic, build quality, warranty, and probably most notably, in wattage. Let's briefly touch on each.

Technology - There are two main types of solar panels and the technology that powers them -  monocrystalline and polycrystalline. In short, monocrystalline panels are more efficient, meaning more energy for a given surface area.  However, efficiency is only one part of the equation - we get into this more in the section below.

Aesthetic - Beauty is in the eye of the beholder, however, most agree that an all black panel is the most attractive. Other common panels have a blue tint and some have a white diamond grid. You can have high efficiency panels with whatever style you prefer. At project solar, we default all builds to all black panels - the generally preferred aesthetic. This can be more expensive, especially when sourcing by yourself without large volume discounts. 

Warranty - This is an area you really want to pay attention to. A good top tier panel will have a 25 year warranty. The cheapest panels will have shorter warranties, and in our opinion, it's not worth it. A good 25 year warranty will guarantee at least 80% of originally stated wattage value by year 25. The actual lifespan of the panels is actually quite a bit longer. 

Build quality - First and foremost, we recommend going with a respected and established brand (Jinko, Aptos, Silfab, LG, Canadian Solar, etc). All these manufacturers have high quality builds, rated to IEC 61215, the industry gold standard. Panels with these ratings should be able to withstand wind, snow, and rain without issue. The companies will also be around long enough to live up to their warranties. 

Wattage - All panels are given a watt rating, which is telling of how much energy your panel will generate in a given hour of direct sun. For residential solar, most panels are in the range of 290-380 watts. 

Efficiency - This watt rating can be converted into a metric showing the efficiency of the panel, which takes into consideration the total size of the panel and the watt rating. Most panels are somewhere between 15-21% efficient. However, given that the majority of residential roof panels are the same size, the wattage is an easier metric to compare.

Wattage and efficiency, given their synced meaning, are often interchanged when comparing the production output of the panel.


Efficiency/Wattage Comparison

Higher wattage means more energy being generated. So the best system has the highest watt panels, right? Not so fast. 

An important metric in solar is Price Per Watt (PPW). 

image comparing cost per watt of different panels

Price Per Watt is simply the cost of the panel divided by the wattage. This metric is far superior to just analyzing the panel wattage because it factors in price. You use this metric when comparing panels for purchase.

Price per watt is also used to compare TOTAL system cost and is calculated the same way - total system cost divided by the watts, giving you the price per watt of the finished system. You would use this when comparing full service vs DIY. Project Solar is around $1.50/watt installed, or around $1.00/watt for DIY (both after incentives). National companies range from $3-5/watt.

Now back to panels... 

Panels in the 320-350 range cost around 50¢/watt. But panels pushing 380-400 watts can be as much as $1-1.50/watt. That means you are as much as 3x more for the same energy generated. 

If this isn't clear, consider this example. 

1.6kW worth of panels consisting of 5 - 320/watt panels at $0.50/watt would cost $800 (this is just the panels and NOT racking, inverters, planing, permits). 
1.6kW worth of panels consisting of 4 - 400/watt panels at $1.00/watt would cost. $1600.
 

These two examples produce THE SAME amount of power, but one system costs twice as much. The ONLY benefit is that there is 1 fewer panel. So this should only be considered when space is extremely limited and when you are REQUIRED to hit a certain kW size lower wattage panels can't hit. 

Doubling the cost, lowers your ROI and time to pay off. 

full service solar install case study

Conclusion

At Project Solar, our goal is solar proliferation by means of making solar not just affordable, but an economic no-brainer. We achieve this by smart system design, efficiently processes, and cutting out the expensive door knocking salesman. 

Don't get suckered in to high efficiency panels. Do your research. Find reputable panels with good warranties and a low cost per watt

For those set on upgrading their panels we have a panel upgrade pricing article, quoted in additional price per watt. 

Or better yet, have us optimize it all for you. We will hold your hand through the entire process, while saving you money through our wholesale relationships. 

calculator call to action