When assessing the cost of solar panels, we must be mindful of the sum outlay of getting the physical objects home from the vendor to having a fully installed and operational power-generating solar system. There is a great disparity in the material cost of solar panels. PV cell cost is determined by a number of variables including power output and quantity purchased. Many vendors quote prices for pre-determined unit sizes (ranging from two panels up to hundreds of panels.) At the time of writing, the cost of solar panels ranges from about $1/Watt to $5/Watt. Cheaper paneling is available from some Chinese vendors, however if purchasing these for use in the US then be sure to compare their quality with domestic items, and ensure you are happy with the way in which any after-sale service concerns may be resolved.

Low wattage paneling is far cheaper than denser, high output paneling (for example, the current market price for Kaneka 60 Watt panels is about $59 per unit which offers an economical $0.98 per Watt; however, the current market price for Evergreen 200 Watt panels is $720 per unit, which converts to $3.60 per Watt.) For this reason, in your pre-planning stage, two important factors must be determined:

a) you must determine how much electricity you use (from previous electricity bills) and how much you want to generate from solar panels; are you looking to replace entirely your existing power generation system and potentially grid-tie the system to sell some excess electricity back to the local supplier?

b) How much directly sun-exposed space do you have available to mount solar panels? If you live in dense residential housing then space may be limited and therefore high-density panelling will be imperative.

Reviewing past electricity bills, you will get an idea of your total annual electricity consumption in kWh. It is very difficult to give a practical example as many houses are serviced by multiple utilities (electricity, natural gas, propane etc.) As an example, an average three-bedroom house that uses natural gas to heat and occupied by two adults and two children might consume 175 kWh electricity per month. Multiplying this figure by 1000 gives 175,000-Watt hours per month used. Dividing this figure by 30 (days in a month) yields 5833 Watts used per day. In order to fully replace the previous electricity setup, solar paneling capable of yielding in the region of 6000 Watts daily will be required. Next, you would need to determine how many hours sunlight your roof (or other mounting position) receives daily. A good, somewhat conservative, guide is to use the amount of sun available close to the shortest day of the year. If this is 4 hours sunlight, then you would need to generate 6000/4 = 1500 Watts per hour. Let us take the Kyocera HD-210-GX-LPU multicrystal panel as an example. At 39”x59”x1.5”, it delivers 210 Watts. To generate the desired 1500 Watts per hour you would need 1500 / 210 ~ 7.15, rounded up to eight whole panels. These panels are 39” x 59” = 2301 square inches, so the minimum mounting space required for these panels would be 8 x 2301 ~ 18,500 square inches, plus room for cable conduits. This is about 127 square feet, or about 11’ x 12‘.

Calculating the aggregate cost of solar paneling is highly dependent on several factors including location, desired output and space available. However, it is hoped that the above will provide a solid basic guide that you might use as a foundation to calculate your own requirements and thence cost.

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