Estimate simple and discounted payback, 25-year savings, and ROI for a residential solar PV system. Factors in the 30 percent federal tax credit (IRA section 25D), state rebates, net metering, panel degradation, utility rate inflation, and annual maintenance.
Solar payback and 25-year ROI
Typical residential install is 5 to 10 kW.
Sunny South: 1,500 to 1,700 kWh per kW. Pacific Northwest: 1,100 to 1,300.
Cost and incentives
Before any incentives. US average is $2.75 to $3.50 per watt.
30 percent through 2032 (IRA section 25D).
Lump-sum rebates only. SREC income is excluded.
Electricity and net metering
US residential average is 16.5 cents per kWh.
100 = full retail rate. NEM 3.0 in California credits closer to 25 to 50 percent (avoided-cost rate).
Long-term assumptions
EIA 20-year average is about 3 percent.
Tier 1 panels: 0.4 to 0.55 percent per year.
Most homeowners spend $0 to $200 per year on cleaning and inverter checks.
Discounted payback
7.8 years
Includes utility rate inflation and panel degradation. Simple payback (today's rate, no degradation): 8.5 years.
Federal tax credit
- $5,400
Net installed cost
$12,600
Year 1 electricity value
$1,485
Year 1 net savings
$1,485
Break-even year
Year 8
25-year ROI
302%
25-year totals
Cumulative savings
$50,626
Total production
212,004 kWh
Year 25 system value
$15,960
Environmental impact
7,650 lb CO2 per year
Based on the EPA eGRID national average of 0.85 lb CO2 per kWh of grid electricity displaced.
Frequently Asked Questions about the Solar Panel Payback Calculator
How does the 30 percent federal solar tax credit work?
The Residential Clean Energy Credit, IRA section 25D, lets you deduct 30 percent of the total installed cost of a qualifying residential solar PV system from your federal tax bill in the year the system is placed in service. The 30 percent rate runs through tax year 2032, then steps down to 26 percent in 2033 and 22 percent in 2034 under current law, after which the residential credit is set to expire. The credit covers panels, inverters, racking, wiring, labor, permits, and a co-installed battery (3 kWh or larger). It is nonrefundable, meaning it cannot drop your tax liability below zero, but unused credit rolls forward to future years. On an $18,000 system that works out to a $5,400 credit at the 30 percent rate, dropping net cost to $12,600 before any state rebates.
Why do net-metering rules matter so much for payback?
Net metering decides what your utility pays for excess solar you push back to the grid, and that single rule can swing payback by years. Full-retail net metering, common in roughly 30 states, credits exported kWh at the same price you pay to import, so every kWh your panels produce is worth your retail rate. Avoided-cost or wholesale rates, used by some IOUs, credit exports at 3 to 7 cents per kWh instead of 15 to 35 cents, which can cut export value by 75 percent. California's NEM 3.0, in effect since April 2023, uses an avoided-cost rate plus time-of-use adders that average about 25 to 30 percent of full retail for most homes, which is why batteries (to self-consume rather than export) are now standard on new CA systems. Set the net-metering credit input to match your utility tariff: 100 for full retail, 25 to 50 for NEM 3.0 in California, 30 to 70 for typical avoided-cost states.
How fast do solar panels actually degrade?
Tier 1 monocrystalline panels from manufacturers like REC, Q CELLS, LG, Panasonic, and SunPower lose about 0.4 to 0.55 percent of rated output per year, with most warranties guaranteeing at least 84 to 92 percent of nameplate power at year 25. SunPower Maxeon premium panels carry the best published curve at roughly 0.25 percent per year and 92 percent year-25 output. At the 0.5 percent default in this calculator, a 6 kW system that started at 9,000 kWh per year drops to about 7,980 kWh by year 25, which is 88.7 percent of original output. Older polycrystalline panels and cheaper Tier 2 brands sometimes degrade 0.7 to 1.0 percent per year, so check the manufacturer's warranty curve before treating the 0.5 percent default as a given.
Why does annual production vary so much by region?
Production per installed kW depends on peak sun hours and weather, both of which differ sharply across the US. Phoenix and the Mojave Desert deliver about 1,700 to 1,900 kWh per installed kW per year. Southern California, Arizona, New Mexico, and West Texas land in the 1,500 to 1,700 range. Most of the South and the Mountain West fall between 1,300 and 1,500. The Northeast and Midwest average 1,150 to 1,350. Seattle, Portland, and the rest of the Pacific Northwest typically produce 1,000 to 1,200 kWh per kW. NREL's PVWatts calculator (pvwatts.nrel.gov) gives a free address-specific estimate that also accounts for roof tilt, azimuth, and shading, so use it to lock in your annualKwhProduction input before running payback math.
What state rebates and SREC markets are worth knowing about?
Beyond the federal credit, a handful of states make solar dramatically more attractive. New Jersey's Successor Solar Incentive (SuSI) pays SREC-II credits of about $90 per MWh for the first 15 years, roughly $1,350 per year on a 10 MWh system. Massachusetts SMART Program credits run $0.18 to $0.32 per kWh of production for 10 years depending on the utility. Illinois Shines pays one-time SREC payments of $50 to $90 per REC, often netting $5,000 to $10,000 upfront on a residential install. New York's NY-Sun program pays $200 to $400 per kW for residential systems in addition to a 25 percent state tax credit (capped at $5,000). Maryland, DC, and Pennsylvania have smaller but still active SREC markets at $40 to $80 per credit. The state-rebates input on this calculator only captures lump-sum rebates, not ongoing SREC income, so add SREC value separately when you compare programs. DSIRE (dsireusa.org) is the canonical database of every active state and utility solar incentive in the US.