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 ground mount installation is roughly 20 percent more expensive than the equivalent roof mount, but because it is usually perfectly oriented (194'azimuth, 35' pitch), it can often be much more productive too. This spreadsheet is for a fixed ground mount using the same modules and inverter as the roof mount example illustrated above.
Due to the higher productivity of a ground mount 23 modules would have actually produced the 9000 kWh production wanted. However fixed ground mounts are nearly always installed in multiples of 3, 4 or 5. A manually adjusted tilting single pole mount will provide even higher productivity (~7%) due to the seasonal adjustability. By far the largest gain for ground mounted NH installations is found by using bi-facial modules. See our winter testing results for these amazing panels here
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. Note that this 4.8 kW array nearly maxes out the NH PUC rebate, and that is why the ROI and Net Cost per kWh figures are so favorable.
The first spreadsheet is for the "typical US 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 (Unitil is higher, NHEC and Liberty lower) 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.