|The FAQ sheet from SEIA covers most of it. [ See the link below to view file ]
For systems put "into service" between 2009 and 2019, the federal tax credit is 30%. That means that for solar electric systems put into service between Jan 1, 2009, and Dec 31, 2019, you will be able to get back 30% of the total cost of the system, with no cap for residential systems. The tax credit is reduced to 26% in 2020 and down to 22% in 2021.
In most of Arizona, you can also get a $2.70 to $3.00 per watt rebate from APS or SRP. The federal 30% tax credit is total cost AFTER the rebate. Just for example, for a 5000-watt system where the total installed cost is $35,000, you would get (for example) $13,500 back from APS, so your cost for the system would be $21,500. You would get a 30% Federal tax rebate on that, so your total cost would be ($21.500 x .70) $15,050.
What "put into service" means is basically when the system goes live, or operational, not when it was purchased.
From IRS Form 5695: Residential Energy Efficient Property CreditYou may be able to take a credit of 30% of your costs of qualified solar electric property, solar water heating property, fuel cell property, small wind energy property, and geothermal heat pump property. This includes labor costs properly allocable to the onsite preparation, assembly, or original installation of the property and for piping or wiring to interconnect such property to the home.
For more information on nationwide local and state incentives, see the Dsireusa.org site: Database of State Incentives for Renewables & Efficiency
As of June 1, 2009, Arizona SRP has cut its rebate to residential customers who install solar photovoltaic systems to $2.70 per watt from $3 per watt. The utility company, which serves more than 905,000 customers in the Phoenix area, is also capping the size of solar-electric systems at 5-kilowatts so it can spread its rebate money to more customers. The APS rebate for AZ customers remains at $3 per for now.
For information on various Arizona rebates, tax incentives, and other solar credits etc see the Arizona Solar Center website. SRP and APS also offer some additional solar incentives, see the same link for more information on those.