|
Categories: ·Batteries ·Homebrew ·Low Power Loads ·Photovoltaic ·Wind Power ·Ocean Power ·Solar Power Community ·Other Solar Power Topics ·All Categories ·Other SignalQ Websites 
|
 The National Renewable Energy Laboratory has an online calculator that will help determine how long it will take to pay for a PV system at the current utility rate for electricity. A variety of factors play into this: where your PV system is on the earth, the efficiency of your power inverter, the tilt of your PV panels and whether or not they track, and the cost of electricity. There calculator is available at this location: PVWATTS: AC Energy and Cost Savings[nrel.gov] After selecting your geographic area, you will see a screen like this: 
We changed the default of 4kW to 10kW and pushed calculate: 
So, at a cost of electricity of 6.4 cents per kWh, the yearly value of a 10kW PV system is $620.74 per year in the Seattle area. Now, a 10kW system is small enough in many cases that this can be a grid-connected (grid-tie) system, and the power that is unused could be sold back to the power company. A 10kW system is large enough that it should be able to provide most of the power for the average house. If we use a 208 Watt Sharp PV Module at a cost of $900, it would cost $43,000 just for the PV panels. At $620/year in savings, it would take 69 years to pay for the panels alone. Note that the cost of panels is going down and the cost of electricity is going up, so these numbers will change quickly. Also, I haven't factored in installation or the inverter. If you want to be off of the grid entirely, then you will also need batteries if you want electricity when the sun isn't shining. |
