Purchasing Solar Panels — Finding the Best Option 

Shopping for solar power systems for the home begins with evaluating the amount of electricity your household consumes. We can help you figure this out, as well as the size and type of solar panel system you will need.

Solar panel sizes

To meet the power requirements of your home, you should ensure that you acquire the right size solar system. For starters, you can choose between 60-cell or 72-cell solar panels. The former, which are 5.4 ft by 3.25 ft, are often used on residential homes or smaller roofs. The latter, measuring 6.5 ft by 3.25 ft, are more suited for use as commercial solar panels, or installed on larger homes. 

How are 60-cell and 72-cell panels different?

60-cell panels have a familiar look and are most commonly utilized in the residential sector. They are lighter and easier to set up on smaller rooftops, thanks to their compact size. 

On the other hand, the 72-cell panels are taller, heavier, and have more cells. Even so, they still share the same width (~3.25 ft) as their 60-cell counterparts.

How to choose the best panels for your home

When purchasing a solar system in the USA (and in the Northern Hemisphere), the solar panels are typically oriented due South (being the most optimal). They may also be oriented East, West, and (rarely) North, but systems facing these directions may not produce at their full potential. When it comes to evaluating a solar proposal, the following factors need to be observed:

  • Efficiency of the entire project 

    • Type of solar panels (Photovoltaic, or PV modules) and their native efficiency rating

    • Efficiency Requirements (do you need to overpay for highly efficient panels, in other words - do you have roof area constraints?

    • Future expansion capability - for example, for the Electric Vehicle (EV)

    • Energy Storage - now or later?

    • Positioning and orientation of the modules being installed 

    • Total system nameplate rating capacity (Watts, or Kilowatts)

  • Electric bill offset %

    • Are there home efficiency improvements that will affect the usage?

    • Are there additional loads in the future, affecting the usage?

    • Payback time (or other Return on Investment (ROI) considerations 

    • Cash flow (in the event the project is financed)

    • Quality of the proposed project

      • Warranty on solar equipment 

        • Solar Inverters

        • PV Modules

        • Solar Mounting Structure 

      • Warranty on Workmanship and Labor

    • Reputation and stability of your solar contractor

      • Time in Business

      • Reviews

      • Ratings

      • Testimonials

      • Professional Affiliations, Licensing, and other credentials

While the full evaluation may require some thought, let’s review the cost basis. As a final result of your estimate, you will receive a Cost per Watt figure. This figure is widely used in the industry as a standardized measure of your roof or ground-mounted solar panel system cost. 

This cost per watt ($/W) is a valuable metric comparing installation prices and energy costs. The lower it is, the more economical your solar installation will be (all other things considered equal). To calculate the cost per watt figure, divide the total cost of the system onto the total watt capacity. For example, a  $25,000, 10 kW solar system costs ($25,000 / 10,000 Watts) = $2.50/Watt (typically pronounced “two-fifty a watt” in the industry).

While a standard, 60-cell module will integrate better in tighter spaces and smaller roofs, a 72-cell module can be a great option for residential installations if the layout permits. For example, a Tesla solar panel measures 420+ Watts in a single unit and is a 72-cell format.  They are often cheaper to install on a large scale (bigger system) as you will be using fewer units.

When purchasing a solar panel system with a battery backup, don’t forget to evaluate other factors for your energy storage, including the efficiency, warranty, and durability of all of your solar system components. 

Solar panel system efficiency explained

The value of your system depends on the efficiency rating of your equipment. Solar conversion efficiency is a measure of the amount of power that a solar panel generates per unit of area. Simply put, higher efficiency solar panels will be smaller for the same wattage compared to a lower efficiency one. It is important to note that the efficiency rating does not affect energy production for rated system size, but only the physical footprint of the system.


For example, a 10 kW solar system in optimal conditions will produce roughly 14,000 kWh per year in Florida, no matter if it consists of 40 x 250 Watt lower efficiency panels or 25 x 400 Watt high-efficiency panels. A 10 kW system is a 10 kW system, regardless of the efficiency of the solar panels that it consists of. The only difference is the number of panels and the size of the system on the roof. Both can be great solar power options. 

What’s the average range for solar panel efficiency?

The typical efficiency ranking for common brands falls between 17 and 20%; some products even go up to 23%. A panel rated at 20% efficiency will convert 20% of the sunlight it receives into usable power. You want to buy solar panels within or above this average efficiency range for the best results.


Example: A 350W panel receiving 6 hours of sunlight per day would produce 2.1 kWh per day, i.e., 350W x 6 hours.

High-efficiency vs low-efficiency panels

High-efficiency products enable you to get more wattage out of fewer units. This allows you to make more of the space you have. Homes with small roofs can still get the power they need despite the limited space.

This is not to say low-efficiency units aren’t worth considering. If you do not have space constraints, fitting low-efficiency panels onto your roof may help you save more money over time. They tend to be more economical on a cost-per-watt basis. You will have a bigger array that costs less to acquire but delivers the same energy yield per rated watt.

Where to buy solar panels that fit your household needs?

At times, homeowners become very focused on per-watt costs. The truth of the matter is that the upfront cost is a considerable part, but it is not the entire aspect of the value of your solar investment. High quality, well-trained labor, high-quality mounting structures, and a company that does right by the community may come at a premium, but are always worth the investment in the long run. Here at PPM, we have already spent the time and conducted the search for some of the best equipment and installers near you. Check out our product offerings and request a quote for a high-quality system that is perfectly fit for your needs.