As you may recall, the house in the above example had a pretty favorable roof exposure (175 ' azimuth with an 8/12 pitch), but what if it didn't? This is where ground mount installations come into play. A fixed angle ground mount installation is roughly 20 percent more expensive than the equivalent roof mount, but because it is perfectly oriented (194'azimuth, 35' pitch) it can often be much more productive too. This spreadsheet is for a fixed ground mount of roughly the same annual kWh production. Note that it is spec'd with bi-facial modules and that because they are more powerful than regular modules fewer of them can be used. Bi-facial modules also have a huge advantage over regular modules during the lower light winter months and this helps even out the seasonal variation.
Note that the Cost per kWh has increased and the ROI (payback) period has become a bit longer. Bear in mind however that the increased cost applies only during the payback period and that the higher power will continue to flow into your home long after the cost of the system has been justified. You'll pay a little more for 8.57 years and be rewarded handsomely for your investment for the next 30 plus!
The first spreadsheet is for the "typical home" as outlined in the preceeding Cost and Incentives tab. The figures in the excel would be most representative of an Eversource customer due to the 18 cent rate shown in the third line. The rate varies somewhat between the different utility companies and while this has no bearing on the initial cost of a solar installation, it does affect the Net Cost per kWh and the Payback Period. A higher utility rate makes the payback period even shorter while a lower rate will extend it a bit. The formulas used to figure those entries are shown in brackets to help you figure out your exact Net kWh and ROI.
Perhaps your home is smaller and your power needs less? This typical Concord home roof has the advantages of both near perfect azimuth and pitch. The 21 cent utility rate suggests that this is a Unitil customer. To keep the comparison consistent to the excels above the modules and inverters have been changed from what was actually installed on this home. There wasn't enough clear space on the customer's roof to totally meet their demand and higher wattage panels were used to get them the best possible solar harvest.