Scenario: a 1,800 sq ft home. 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
Quick answer: A typical 1,800 sq ft home that uses about 11,000 kWh a year needs roughly 18 solar panels (a 7.2 kW system using 400 W panels). Depending on local sunshine, the count ranges from about 14 panels in Phoenix to 23 in Seattle. In 2026 a 7.2 kW system costs about $18,700–$24,200 before incentives, and homeowners who buy a system no longer receive the 30% federal tax credit, which ended on December 31, 2025.
Square footage is only a rough proxy. Your electricity use, your local peak sun hours and the wattage of the panels decide the real number, and this guide shows exactly how to calculate each one. All prices, rates and incentive rules below are as of October 2026.
Key takeaways
Panels: about 18 at 400 W (7.2 kW); 14–23 depending on location.
Cost: about $18,700–$24,200 before incentives in 2026.
Federal credit: none for purchased systems installed after 2025; state incentives vary.
Payback: about 9–12 years at the U.S. average electricity price.
⚡ System Size
How to Calculate Solar Panel Count for a 1,800 sq ft Home
Start with your annual electricity use in kilowatt-hours (kWh) from 12 months of utility bills, then divide by how much energy one kilowatt of panels produces per day where you live.
Formula:
Panels needed = Annual kWh ÷ 365 ÷ (Peak sun hours × 0.83) ÷ Panel wattage in kW
The 0.83 factor is a system-efficiency (derate) assumption covering inverter, wiring, temperature and soiling losses, in line with the default loss assumptions in NREL’s PVWatts calculator. Peak sun hours are the daily equivalent hours of 1,000 W/m² sunlight at your location.
Worked example (11,000 kWh/year, 400 W panels):
Daily need: 11,000 ÷ 365 = 30.1 kWh/day
Phoenix, AZ (about 6.54 peak sun hours): 30.1 ÷ (6.54 × 0.83) = 5.55 kW, or about 14 panels
Seattle, WA (about 3.95 peak sun hours): 30.1 ÷ (3.95 × 0.83) = 9.19 kW, or about 23 panels
City
Peak sun hours/day
System size needed
Panels (400 W)
Phoenix, AZ
6.54
5.6 kW
~14
Denver, CO
5.66
6.4 kW
~16
Boston, MA
4.70
7.7 kW
~19
Chicago, IL
4.27
8.5 kW
~21
Seattle, WA
3.95
9.2 kW
~23
Illustrative calculation using the formula above. Sun-hour values are annual PVWatts v8 results for each city; your roof’s tilt, direction and shade will change them.
Data visualization
Panels needed for an 1,800 sq ft home by city (400 W panels, 11,000 kWh/yr, 0.83 system efficiency). Phoenix needs about 14 panels and Seattle about 23. Source: our calculation from annual NREL PVWatts v8 peak sun hours.
Chart takeaway: Sunshine, not house size, drives the spread. With the same 11,000 kWh of annual use, Seattle needs about 23 panels versus about 14 in Phoenix, roughly 64% more. Use the typical 18-panel figure only as a starting point and confirm your number with your own address in NREL’s PVWatts calculator.
Panel wattage matters too. Many residential panels sold in 2026 are rated 400–450 W. A 7.2 kW array is 18 panels at 400 W but only 16 panels at 450 W, so always compare quotes by system kW and estimated first-year kWh, not by panel count.
Why two quotes show different panel counts:
Different panel wattages.
Different production assumptions (tilt, shading, efficiency losses).
One installer targeting 90% of your usage and another 100%.
Ask every installer for the estimated first-year kWh production and the 12-month usage figure they used. If a quote is issued without looking at your utility bills, treat it with caution.
The savings calculator loads your state's average electricity rate, sun hours and net-metering rule. Then enter your own bill and installer quote.
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💰 System Cost
What Does a Solar System for a 1,800 sq ft House Cost in 2026?
A 7.2 kW system costs about $18,700–$24,200 before incentives in 2026. The upper end reflects the SEIA/Wood Mackenzie national residential average of $3.36 per watt (Q2 2026); the lower end reflects roughly $2.60 per watt, in line with EnergySage marketplace averages of about $2.58–$2.60 per watt. Prices vary by installer, equipment, roof complexity and state.
Solar system cost by size (2026, before incentives)
System size
Panels (400 W)
Cost range ($2.60–$3.36/W)
Est. annual output*
5 kW
13
~$13,000–$16,800
~7,500 kWh
6 kW
15
~$15,600–$20,200
~9,100 kWh
7.2 kW
18
~$18,700–$24,200
~10,900 kWh
8 kW
20
~$20,800–$26,900
~12,100 kWh
10 kW
25
~$26,000–$33,600
~15,100 kWh
*Output assumes about 5 peak sun hours per day and 0.83 system efficiency (roughly 1,500 kWh per kW per year). Actual output depends on location, tilt and shade.
Is the 30% Federal Solar Tax Credit Still Available in 2026?
For homeowners who buy a system, no. The One Big Beautiful Bill Act, signed July 4, 2025, ended the Residential Clean Energy Credit (Section 25D) for expenditures made after December 31, 2025. The IRS treats a system as “made” when installation is complete, so a system finished in 2026 does not qualify even if you signed a contract earlier.
What still exists at the federal level:
Systems completed by December 31, 2025: eligible for the 30% credit on your 2025 tax return, including any unused amount carried forward.
Leases and power purchase agreements (PPAs): the company that owns the system may claim the commercial Section 48E credit if construction began by July 4, 2026, or if the system is placed in service by December 31, 2027. Some providers pass part of that value to you through lower payments, but the credit is not yours to claim.
State and utility programs were not changed by the federal law, and they now matter more. Examples:
New York: a state income tax credit of 25% of system cost, capped at $5,000, plus NY-Sun incentives.
Massachusetts: a state tax credit of 15% of system cost, capped at $1,000, plus the SMART production incentive.
California: the current net billing tariff (often called NEM 3.0) pays lower rates for exported power than the earlier net metering program, which lengthens payback. Check utility and local programs for any rebates.
How Many kWh Does a 1,800 sq ft House Use Per Year?
Your own 12-month bill history is the only number that matters for accurate sizing. For context, the U.S. Energy Information Administration (EIA) reports that the average U.S. home uses roughly 10,400–10,800 kWh per year (about 870–900 kWh per month), and EIA’s Residential Energy Consumption Survey puts homes in the 1,500–1,999 sq ft band at about 900 kWh per month. This guide uses 11,000 kWh per year as a planning figure for an 1,800 sq ft home.
Climate and fuel type create large gaps. In EIA’s 2024 state data, average residential use ranged from roughly 500 kWh per month in California to about 1,100 kWh per month in Texas and Florida.
Changes that raise usage are worth building into the system size now:
Electric vehicle: an EV driven about 12,000 miles a year at roughly 0.3 kWh per mile adds about 3,600 kWh per year.
Heat pump or electric water heater: can add substantially, especially if replacing gas.
Pool pump, home office or second refrigerator.
Rule of thumb: at about 5 peak sun hours per day and 0.83 system efficiency, 1 kW of panels produces about 1,500 kWh per year, so a 7.2 kW system produces about 10,900 kWh, close to the 11,000 kWh planning figure.
⏱️ Payback
How Long Does It Take Solar Panels to Pay for Themselves on a 1,800 sq ft House?
Base case: a 7.2 kW system producing about 10,900 kWh a year offsets roughly $2,000 a year at the recent U.S. average residential price of about 18.3 cents per kWh (EIA: 18.34 cents in June 2026). With no federal credit, simple payback is:
Lower-cost case: $18,700 ÷ $1,995 ≈ 9.4 years
Higher-cost case: $24,200 ÷ $1,995 ≈ 12.1 years
These figures assume every kWh is credited at the full retail price (full net metering) and no electricity price escalation.
Your electricity price changes the answer more than anything else. For the same system:
At Florida-level prices (about 15.1 cents/kWh), savings are about $1,650 a year, so payback is about 11–15 years.
At Massachusetts-level prices (about 28.8 cents/kWh in May 2026), savings are about $3,140 a year, so payback is about 6–8 years, before state incentives.
Data visualization
Average residential electricity price by state, June 2026. California at 34.74 cents/kWh is about 2.6 times Nevada at 13.11 cents/kWh; the U.S. average is 18.34 cents/kWh. Source: EIA Electric Power Monthly, Table 5.6.A.
Chart takeaway: California’s June 2026 average price (34.74¢) was about 2.6 times Nevada’s (13.11¢), and solar savings per kWh scale with that price. The caveat is export compensation: where utilities pay less than the retail rate for exported power, as under California’s net billing tariff, payback is longer than a simple price comparison suggests.
Net metering and export rates. Under one-for-one net metering, exported power earns a full retail credit. Where export credits are lower, homes that use more of their solar production during the day (or add a battery) keep more of the value. Check your utility’s current tariff before relying on any payback estimate.
Panel lifespan. NREL’s analysis of field data found a median degradation rate of about 0.5% per year. A 400 W panel would produce roughly 390 W after five years and about 350 W after 25 years. Most manufacturers warrant panels for 25 years.
Financing example. A $21,000 loan at 7% over 20 years has a payment of about $163 per month, compared with about $166 per month in average bill savings in the base case. Loan rates, fees and terms vary, so treat this as an illustration, not a quote.
Is Solar Worth It for a 1,800 sq ft House? What 25-Year ROI Shows
For many homeowners, yes, though the margin is narrower than it was with the 30% federal credit. The strongest cases combine high electricity prices, good sun and a state incentive. The weakest combine low rates, heavy shade and reduced export credits.
25-year estimate for a 7.2 kW system bought in 2026:
Electricity produced: about 256,000 kWh (10,900 kWh in year 1, declining 0.5% per year)
Value at a flat 18.3 cents/kWh: about $46,900
System cost: $18,700–$24,200
Estimated net gain: about $22,700–$28,200
This estimate assumes no electricity price increases, full retail credit for all production and no financing costs. It does not include an inverter replacement (string inverters often need replacing once during a system’s life), maintenance, roof work or insurance and tax effects. State incentives would improve the result; rising utility prices would improve it further.
Data visualization
Cumulative net cash position for a 7.2 kW system over 25 years, no federal credit. Break-even arrives in year 10 (lower-cost case, $18,700) or year 13 (higher-cost case, $24,200), ending near +$28,200 and +$22,700. Source: our calculation at 18.3 cents/kWh with 0.5% annual degradation; price inputs from SEIA/Wood Mackenzie and EIA.
Chart takeaway: The lines cross zero in year 10 for the lower-cost case and year 13 for the higher-cost case, and end near +$28,200 and +$22,700 at year 25. Installed price per watt is the biggest lever you control, so collect at least three quotes and compare them by price per watt and estimated first-year kWh.
Buy, loan or lease? Buying with cash or a loan gives you ownership and any state incentives but no federal credit in 2026. A lease or PPA lowers upfront cost and may reflect the Section 48E credit that the owner can claim, but you typically give up ownership and should check the payment escalator, contract length and what happens if you sell the home.
Before signing, use our solar savings calculator to compare scenarios with your actual utility rate and quote. You can also review nearby sizes in our guides for 1,700 sq ft and 1,900 sq ft homes.
System prices: Wood Mackenzie and SEIA U.S. Solar Market Insight (residential benchmark $3.36/W, Q2 2026); EnergySage marketplace averages (about $2.58–$2.60/W).
Production modeling: NREL PVWatts calculator; city sun-hour values are annual PVWatts v8 results as compiled by third-party publishers. Verify your address directly in PVWatts.
Degradation: NREL, Photovoltaic Degradation Rates: An Analytical Review (median about 0.5% per year).
Federal credit status: IRS Residential Clean Energy Credit page; Public Law 119-21 (One Big Beautiful Bill Act).
State incentives:DSIRE and state program pages (New York, Massachusetts).
Method: Panel counts and payback figures are our calculations from the assumptions stated in each section (11,000 kWh/yr, 400 W panels, 0.83 system efficiency, 18.3¢/kWh, 0.5% annual degradation). They are estimates, not quotes, and not tax or financial advice.
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Direct answers for US homeowners — sized for a 1,800 sq ft home.
A typical 1,800 sq ft home using about 11,000 kWh a year needs roughly 18 panels rated at 400 watts (a 7.2 kW system). The count ranges from about 14 panels in Phoenix to about 23 in Seattle because of differences in peak sun hours. Your actual 12-month electricity use, roof orientation, shading and panel wattage decide the final number, so size from your utility bill rather than square footage.
A 7.2 kW system costs roughly $18,700–$24,200 before incentives at about $2.60–$3.36 per watt; SEIA and Wood Mackenzie put the national residential average at $3.36 per watt in Q2 2026. The 30% federal Residential Clean Energy Credit (Section 25D) ended for systems placed in service after December 31, 2025, so purchases in 2026 get no federal credit. State incentives, such as New York's 25% credit capped at $5,000, may still apply.
At the U.S. average residential price of about 18.3 cents per kWh, a 7.2 kW system saves roughly $2,000 a year, which gives a simple payback of about 9 to 12 years with no federal credit. Payback is faster where electricity is expensive (roughly 6 to 8 years at Massachusetts-level prices, before state incentives) and slower where it is cheap (about 11 to 15 years at Florida-level prices). Reduced export credits can add years.
Often yes, but the margin is smaller and depends on your electricity price, sunshine and incentives. Under the assumptions in this guide, a 7.2 kW system earns an estimated $22,700–$28,200 net over 25 years, before inverter replacement and maintenance. Leases and PPAs are an alternative: the system owner may still claim the commercial Section 48E credit and pass part of the benefit to you, but deadlines apply and contracts vary, so compare terms carefully.
Yes. East- and west-facing roofs typically produce about 10–20% less than a well-tilted south-facing roof, so you may need a few more panels to reach the same annual output. Heavy shading or a steep north-facing roof can reduce production much more. Run your exact address, tilt and azimuth through NREL's free PVWatts calculator or ask installers for a shade-adjusted production estimate.
Same usage, bill-based guide
Your 1,800 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).
Square footage
Used only as a rough usage proxy: 1,800 sq ft × 0.4495 kWh/sq ft/month. EIA: average US residential customer used about 899 kWh/month (2022). Site assumption: that usage corresponds to a ~2,000 sq ft home (0.45 kWh per sq ft per month). Square footage is only a rough proxy — size from your actual kWh.
Estimates only — not tax, legal or financial advice. Get at least three installer quotes and confirm incentives with your utility and a tax professional.