Assumes 3%/yr rate increases, 0.5%/yr panel degradation and no federal tax credit (the 30% §25D credit ended for systems installed after Dec 31, 2025). How we calculate
Data approachEIA rates · NREL sun hours · 2026 federal policy · methodology
Most 1,700 sq ft homes need roughly 13 to 25 solar panels (400 W each) to cover their electricity use. A home using 9,000 kWh per year needs about 17 panels (6.8 kW). Square footage is a weak predictor: the number of people, air conditioning, electric heating, water heating, and EVs matter more. The EIA reports that the average U.S. residential utility customer used 10,791 kWh in 2022, or about 899 kWh per month. This guide shows the math, with assumptions stated, so you can check it against your own bills before you talk to an installer.
Important 2026 change: the 30% federal tax credit for homeowner-owned solar (Section 25D) no longer applies to systems installed after December 31, 2025. Older guides that show an “after tax credit” price are out of date.
⚡ System Size
How Many Solar Panels Does a 1,700 sq ft Home Need?
Short answer: about 17 panels of 400 W (6.8 kW) for a home using 9,000 kWh per year, at 4.5 peak sun hours and 80% system efficiency. Your count moves up or down with your annual usage.
The sizing formula is:
System size (kW) = Annual kWh ÷ (Peak sun hours × 365 × 0.80)
Panels = System size (kW) ÷ Panel wattage in kW
For the example home: 9,000 ÷ (4.5 × 365 × 0.80) = 6.85 kW, which is about 17 panels at 400 W (6.8 kW). The 0.80 factor is a conservative allowance for wiring, inverter, temperature, and soiling losses. NREL’s PVWatts tool uses its own loss assumptions, and your real sun hours depend on your location, roof angle, and shade. Sun hours can change the result by tens of percent between regions, so use PVWatts for your address.
Annual use
Monthly use
System size
400 W panels
7,000 kWh
583 kWh
5.3 kW
13
9,000 kWh
750 kWh
6.8 kW
17
10,800 kWh (U.S. average)
900 kWh
8.2 kW
21
13,000 kWh
1,083 kWh
9.9 kW
25
Calculated at 4.5 peak sun hours and 80% system efficiency. 10,791 kWh is the EIA 2022 residential average, rounded.
Roof space is rarely the limit. A standard residential panel covers roughly 18 to 22 sq ft, so 17 panels need about 300 to 375 sq ft of usable, unshaded roof. A 1,700 sq ft single-story home typically has a roof larger than its floor area. Use our solar system size calculator to test your own usage and location. Sizing guides for nearby homes: 1,600 sq ft and 1,800 sq ft.
Data visualization
Panels needed by annual usage. A 9,000 kWh home needs about 17 panels (6.8 kW); the U.S. average of 10,791 kWh needs about 21. Source: EIA 2022 usage, NREL-style sizing at 4.5 sun hours.
Chart summary: Panel count scales directly with electricity use. Moving from 7,000 to 13,000 kWh per year raises the requirement from 13 to 25 panels. The example 9,000 kWh home sits near 17 panels. If your bills show higher use, for example from an EV or electric heating, plan for the higher bar, and check that your roof can hold that many panels.
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💰 System Cost
What Does Solar Cost for a 1,700 sq ft Home in 2026?
Short answer: about $17,000 to $24,000 before incentives for a 6.8 kW system, with no federal credit for purchased systems. Published 2026 price estimates for U.S. residential solar mostly fall between $2.50 and $3.50 per watt. Competitive marketplace quotes have averaged lower than cash prices from a single installer, so quotes can differ by thousands of dollars. Battery storage costs extra.
System size
400 W panels
Cost at $2.50/W
Cost at $3.00/W
Cost at $3.50/W
5.2 kW
13
$13,000
$15,600
$18,200
6.8 kW
17
$17,000
$20,400
$23,800
8.4 kW
21
$21,000
$25,200
$29,400
10.0 kW
25
$25,000
$30,000
$35,000
Arithmetic from the stated per-watt prices; not a quote. Prices before any state, utility, or local incentive.
Federal incentives changed sharply:
Homeowner-owned systems (cash or loan): the Section 25D credit ended for expenditures after December 31, 2025. The IRS notes that 2025 projects can still be claimed on the 2025 return using Form 5695.
Leases and PPAs: the installer owns the system and may claim the commercial Section 48E credit. Under current law, solar projects that began construction after July 4, 2026 generally must be placed in service by December 31, 2027. The savings you see depend on the contract.
State and local programs: some states, utilities, and cities offer rebates, performance payments, or tax exemptions. Search your state in DSIRE.
Use our solar tax credit calculator only for systems still eligible for a credit, such as a lease offer that quotes one.
Solar vs utility company · 25-year comparison
25-year totals: 3%/yr rate increases, 0.5%/yr degradation, no federal credit. Methodology
Short answer: higher-wattage panels reduce the panel count, not the system size you need. For the same 6.8 kW target:
Panel rating
Panels for about 6.8 kW
300 W
23
350 W
20
400 W
17
450 W
16
Panels = 6,800 W ÷ panel rating, rounded up.
Fewer panels can reduce racking and labor, and they leave roof space for later additions. They do not change how many kWh the system produces. Compare quotes by price per watt and expected annual kWh, not by panel count. Microinverters or power optimizers limit the effect of partial shade on other panels. If part of your roof is shaded for much of the day, ask installers for a shade analysis and a production estimate based on your roof.
Panels degrade slowly. NREL’s analysis of published field data found a median degradation rate of about 0.5% per year, so a system loses roughly 12% of its output over 25 years. The payback model below includes this loss.
⚡ System Size
How Long Does Solar Take to Pay Back on a 1,700 sq ft Home?
Short answer: about 12.5 years at the national average rate, about 7 to 8 years at roughly 30 cents per kWh, and about 14 to 15 years at roughly 15 to 16 cents. Electricity price is the biggest driver of payback.
The model uses the same 6.8 kW system in every state, $3.00 per watt ($20,400), no federal credit, 8,935 kWh of first-year output (4.5 sun hours, 80% efficiency), and full retail credit for every kWh. Rates are EIA July 2026 average residential prices.
Area
Avg rate (cents/kWh)
First-year savings
Simple payback
California
33.61
$3,003
6.8 years
Massachusetts
30.49
$2,724
7.5 years
New York
29.90
$2,672
7.6 years
U.S. average
18.31
$1,636
12.5 years
Colorado
17.00
$1,519
13.4 years
Texas
15.88
$1,419
14.4 years
Florida
15.03
$1,343
15.2 years
Rates: EIA Electric Power Monthly, Table 5.6.A, July 2026. Savings = 8,935 kWh x rate. A single month’s average rate is not the same as your annual bill; use your own tariff.
Two limits matter. First, the model credits every kWh at the retail rate, which overstates savings where export credits are lower. California’s net billing rules for new applicants (NEM 3.0, since April 2023) pay much less for exported power, so the California figure is a best case. Second, it holds sun hours and price per watt constant; sunnier states produce more, and some states cost more per watt.
Data visualization
Simple payback by average residential rate. The same $20,400 system pays back in 6.8 years in California but 15.2 in Florida. Source: EIA Electric Power Monthly, July 2026.
Chart summary: The same system pays back almost twice as fast at 30 cents per kWh as at 15 cents. Massachusetts, New York, and California land near 7 years in this simplified model. Texas, Florida, and Colorado land between 13 and 15 years. Treat the California bar as a best case, and check your utility’s export rules and your own rate before relying on any payback figure.
The next chart shows cumulative cash flow at the U.S. average rate over 25 years.
Data visualization
25-year cumulative cash flow. A $20,400 system at the 18.31¢/kWh U.S. average breaks even in year 13 and nets about $18,100 by year 25. Source: EIA July 2026 rates, 0.5% NREL degradation.
Chart summary: With flat electricity prices, the $20,400 system breaks even in year 13 and ends year 25 about $18,100 ahead. If rates rise 2% per year, an illustrative scenario and not a forecast, break-even moves to year 12 and the 25-year net rises to about $28,700. Neither line includes financing costs, maintenance, or a possible inverter replacement, since string inverters often carry warranties shorter than the panels.
Short answer: often yes, but the case is narrower than when the 30% credit applied. Solar is strongest where rates are high, exports earn close to retail, your roof is sunny and sound, and you will stay long enough to reach payback.
Solar tends to make sense if:
Your electricity rate is well above the national average, or your usage is high.
Your utility offers full retail net metering, or you use most of your solar power during the day.
Your roof has many years of life left. Replacing a roof later means paying to remove and reinstall the array.
You plan to stay past the payback period.
Solar is a weaker fit if:
Your rate is about 15 cents per kWh or lower, as in parts of the South and Midwest.
Your roof is heavily shaded, or most panels would face north.
Your utility pays low rates for exported power and you are away during the day.
You may sell within a few years.
Resale value can add to the case. A 2015 Lawrence Berkeley National Laboratory study of homes in eight states estimated a premium of about $4 per watt for owned solar systems; the study is dated, and results vary by market. Get at least three itemized quotes, compare price per watt and estimated annual kWh, and model your own numbers with our solar savings calculator and solar ROI calculator.
DSIRE for state and utility incentives and net metering rules.
Lawrence Berkeley National Laboratory: Tracking the Sun for U.S. installed-price data; 2026 per-watt ranges here are rounded from published industry estimates.
Method: all panel counts, costs, paybacks, and cash flows are our own calculations from the stated assumptions. They are estimates, not quotes or guarantees; this is not tax or financial advice.
Related calculators
Free tools for US homeowners — instant results, all 50 states.
Direct answers for US homeowners — sized for a $125/month electric bill.
Most 1,700 sq ft homes need about 13 to 25 panels of 400 W, depending on electricity use, not square footage. A home using 9,000 kWh a year needs about 17 panels (6.8 kW) at 4.5 peak sun hours and 80% system efficiency. Use 7,000 kWh and you need about 13; use the EIA U.S. residential average of 10,791 kWh and you need about 21. Read your last 12 months of bills for annual kWh, then run your address in NREL PVWatts, because sun hours vary by location.
A typical 6.8 kW system costs about $17,000 to $24,000 before incentives in 2026, based on roughly $2.50 to $3.50 per watt. There is no federal tax credit for homeowner-owned systems: the 30% Residential Clean Energy Credit (Section 25D) ended for expenditures after December 31, 2025, under the One Big Beautiful Bill Act. Leases and power purchase agreements can still pass through a commercial credit if the installer qualifies, but eligibility has deadlines. Check state, utility and local incentives in DSIRE before signing.
At the July 2026 U.S. average residential rate of 18.31 cents per kWh, a $20,400 system pays back in about 12.5 years, assuming full retail credit for all output. At roughly 30 cents per kWh, as in New York and Massachusetts, the same model gives about 7 to 8 years. At 15 to 16 cents, as in Texas and Florida, it gives about 14 to 15 years. Payback is longer where exports earn less than retail.
Buying gives you ownership and all the savings, but with no federal credit your upfront cost is the full price. A lease or PPA has little or no upfront cost, and the installer may claim a federal commercial credit and share part of it through lower rates. Third-party savings are usually smaller over 25 years, and contracts can include annual price escalators and transfer terms when you sell. Compare the total 25-year cost of each offer, not only the first-year payment.
Net metering can change payback by several years. Where utilities credit exports at the full retail rate, each exported kWh offsets a kWh you would buy later. Where exports earn a lower rate, savings depend mostly on how much solar power you use as it is produced. California, for example, moved new applicants to a net billing tariff (NEM 3.0) in April 2023 with much lower export credits. Check your utility's current tariff in DSIRE before sizing your system.
Same usage, bill-based guide
Your 1,700 sq ft House target maps to roughly a $125/month electric bill nationally.
18.19¢/kWh — US average residential price. Source: EIA Electric Power Monthly, Table 5.6.B (year-to-date through July 2026), residential average retail price (July 2026) (EIA)
Solar production
4.5 peak sun hours/day × 0.82 system derate. Approximate state-average daily solar resource (peak sun hours) based on NREL solar resource data (NSRDB); not location-specific — use NREL PVWatts for an address-level estimate. (NREL PVWatts)
Installed price
$3.00 per watt before incentives. Blended 2026 US residential installed price used by this site; EnergySage marketplace reported about $2.60/W (mid-2026); full-market medians are higher.
Federal tax credit
$0 for homeowner-owned systems installed in 2026 — the 30% §25D credit ended Dec 31, 2025 (IRS)
Net metering
National blend — solar assumed to offset 75% of the bill (87% in full-retail net-metering states, 55–70% elsewhere).
Estimates only — not tax, legal or financial advice. Get at least three installer quotes and confirm incentives with your utility and a tax professional.