37 months (3 years) like you said, however, the Detroit news article is leaving out quite a bit of information.
How much did the solar panels cost? Did the $8,800 in "personnel and contractual services" include everything that was required to hook the system up and get it running?
Also, as steve said, what are the maintenance costs?
But one thing that ANYONE who has an ounce of knowledge about physics or power should be asking about energy is why the Detroit News makes a statement like
An online tracking system reported that the hybrid energy system that went into service Aug. 16 had produced 262 kilowatts of power as of Thursday.
Indeed, kilowatt is a unit of power, but power is how much energy is delivered in a given time period. Look at your energy bill. You wouldn't use and pay for 262 kilowatts of power, you might however pay for 262 kilowatt-hours of energy (943200000 Joules). Let's look at the actual savings while we are at it.
Dates: 16 AUG - 2 SEPTEMBER (I'm assuming 2 September because the article date says 7 september, so the last thursday would be 2 sep) - 17 or 18 days, depending on whether you include the last day or not.
Energy: 262 KWH
So let's see what this is per day... 262KWH/17Days (I'll be generous) = 15.4 KWH/Day
So for a period of 30 Days, that's 462KWH.
What's the cost per KWH? Well, I know different outfits have different plans, but based off a rough estimate from my bill, included all "energy optimization" charges and bullshit, the going rate for 1KWH is roughly $0.1318325.
So based on those numbers, the amount saved is approx $60.90. Of course we didn't even address the fact that they aren't even using all that energy, as the article states that:
When the Township Hall is closed on weekends, the energy generated is fed back into the electrical grid, Archinal said.
Even if you double the cost, and use all that energy in a month, it's only $121.81 - a FAR cry from the claimed $3000-4000 in savings, or even the $2800 based on 20% of $14,000 in energy costs.
$103,719 / $121.81/mo = 851.48 Months, or 70.9 years.
Either someone was smoking crack when they came up with the 20% figure, or homeboy is saying they use more energy than they actually do.