Siksukr, Let me fill in some detail and then hopefully the "one and done" statement will make more sense. If you see a flaw in my thinking please let me know why with details. This argument was pointed out to me recently by a very knowledgeable customer and I'm always anxious to learn more!
An 8400 watt array roof mounted on a roof with a good clear southern exposure will produce about 10-10,500 kWh per year. A perfectly oriented roof or ground mount will produce about 11,000. This can be verified
here at the Federal government's official research lab. To come up with a figure for the amount of cash the solar array will save annually just multiply the kWh by the utility rate. Let's use the lower 10,000 kWh figure to be conservative, the annual savings for a Eversource customer would be $1,800 , and the savings for a Co-op customer would be $1,400
Our pricing for a straight ahead roof array is currently $2.35/dc watt, so an 8,400 watt (the total of the panel ratings) array would have an gross upfront cost of just under $20,000.
To get that $20,000 dollar funding let's make another assumption and say that the client is in a 25% net tax bracket and needs to generate $26,700 in pretax income to come up with $20,000 in cash funds ($20,000/.75). The simple one and done figure is $27,700 in pretax income needed to cover the upfront cost of the solar array installation.
The customer will be able to claim a 30% tax
credit on their next tax return and all the formulas I'm familiar with deduct this from the gross
after tax cost making the system a net cost of $14,000. I have only average accounting knowledge and am not sure where the credit should be entered into the after and pretax figuring above, should it be the $27,700 pretax income -6,000? or should it be the $20,000 gross -6,000/.75?? There is a huge difference. To keep it simple and be conservative let's stick with the $27,700 as the amount needed in pretax income to install the solar array.
A solar array is assumed to have a useful lifespan in excess of 40 years, but to again be conservative let's use 25 years because that is the warranty of most solar modules (aka panels) In 25 years of paying utility bills you will have sent $45,000 25 years x $1,800) in
after tax dollars to Eversource to pay your monthly bills ($35,000 Co-op) ...and that is assuming that the utility rate never goes up. To generate the pretax income needed to pay those Eversource bills for 25 years you would have need to generate $60,000 in pretax income. Conservatively the solar system will save the client $32,300 in pretax income over 25 years. Would you agree??