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
A 1,750 sq ft roof can typically fit about 12 to 29 solar panels (4.8–11.6 kW with 400 W panels). The average U.S. home needs about 21 panels (8.4 kW) to offset roughly 10,800 kWh a year. On a simple, unshaded roof the space usually isn’t the limit; on a complex or shaded roof it can be.
This guide reads “1,750 sq ft roof” as 1,750 sq ft of total roof surface. If you mean a 1,750 sq ft house, your roof area depends on stories and pitch, and the panel count you need depends on electricity use. Both are covered below.
Last updated October 1, 2026. Figures are modeled estimates from the assumptions listed in the methodology section, not installer quotes.
Quick answer
Result
Panels that physically fit
12–29 (layout-dependent)
Panels an average home needs
~21 (8.4 kW at 4.5 peak sun hours)
Cost before incentives
~$21,840 at $2.60/W
Federal credit for purchased systems
None for 2026 (ended Dec 31, 2025)
Modeled simple payback
~11 years at flat rates
🏠 Roof & Layout
How Much of a 1,750 sq ft Roof Is Usable for Solar?
Not every square foot of roof can hold panels. The National Renewable Energy Laboratory (NREL) analyzed lidar data for 128 cities and found that about 26% of the total roof area on small buildings is suitable for solar, after accounting for shading, orientation, and obstructions. A typical 400 W panel is roughly 67 × 44 inches, or about 21 sq ft (sizes vary by model).
Applying that to a 1,750 sq ft roof, with three illustrative layouts:
Complex or shaded roof (15% usable): ~262 sq ft → 12 panels (4.8 kW)
NREL average (26% usable): ~455 sq ft → 21 panels (8.4 kW)
Simple gable with one clear south face (35% usable): ~612 sq ft → 29 panels (11.6 kW)
The 15% and 35% cases are modeling assumptions for illustration. A 35% share is plausible for a simple gable where one face is about half the roof, minus setbacks and vents. Local fire codes often require clear pathways near the ridge and roof edges (commonly around 3 ft), so your jurisdiction’s rules set the real number.
Data visualization
Panels that fit on a 1,750 sq ft roof under three usable-area assumptions. Calculated as usable area ÷ 21 sq ft per 400 W panel, rounded down. The 26% case uses NREL’s average; 15% and 35% are illustrative. Source: NREL (26% figure); author calculation.
Chart summary: Usable share matters more than total roof size. The same 1,750 sq ft roof holds 12 panels in a shaded, multi-section layout and 29 in a clean gable. At the NREL average, it holds about 21 panels, enough for an average home’s electricity use. An installer’s site assessment or a satellite roof model gives your actual number.
Roof area from house size. If you know floor area instead, roof surface is the building footprint times a pitch factor, plus overhangs. The pitch factor is √(1 + (rise/12)²):
Roof pitch
Surface vs. flat footprint
4:12
×1.05
6:12
×1.12
8:12
×1.20
12:12
×1.41
A two-story home has roughly half the roof footprint of a single-story home with the same floor area, so a 1,750 sq ft two-story house can have well under 1,750 sq ft of roof.
Use our solar system size calculator to estimate your panel count from your roof dimensions and local sun hours.
⚡ System Size
How Many Panels Does the Average Home Need?
Panel count follows electricity use, not square footage. The standard planning formula is:
The 0.80 is a conservative derate for inverter, wiring, temperature, and soiling losses. For a home using the EIA’s national average of 10,791 kWh a year, with 400 W panels and 4.5 peak sun hours (a mid-range planning value, not a national statistic):
Peak sun hours vary by location, so the count moves a lot:
Data visualization
Panels needed to produce 10,791 kWh a year at different peak sun hours. 400 W panels, 0.80 derate, rounded up. Source: EIA (usage); author calculation.
Chart summary: Moving from a cloudy-climate 3.5 sun hours to a desert-climate 6.5 cuts the panels needed from 27 to 15 for the same electricity use. In sunnier regions a 1,750 sq ft roof has spare space; in cloudier regions the requirement can approach what a constrained roof can hold. Check your location’s value in NREL’s PVWatts calculator.
Panel wattage changes the count, not the energy. Higher-wattage panels reach a target system size with fewer panels:
The savings calculator loads your state's average electricity rate, sun hours and net-metering rule. Then enter your own bill and installer quote.
Free · No signup · Runs in your browser
⚡ System Size
How Roof Orientation and Pitch Change the Layout
In the continental U.S., south-facing planes produce the most per panel. East- and west-facing planes typically produce roughly 10–20% less annually, with about 15% a common figure. Southeast and southwest faces lose less, and tilt matters less than direction. North-facing planes lose substantially more and are usually skipped.
If your only open roof planes face east and west, add roughly 10–20% more panels to match the same annual kWh. On a 21-panel baseline, that is about 23–25 panels, which still fits within the 26%-to-35% usable-area cases above. Split east–west arrays can also spread production across morning and evening, which can help under time-of-use rates.
Flat or low-slope roofs use tilt-up racking, which adds hardware cost but lets the installer choose direction. Microinverters or optimizers can recover production where parts of an array are shaded, so ask installers about module-level electronics on complex roofs.
💰 Incentives
Is There a Federal Solar Tax Credit in 2026?
Not for systems you buy. The 30% Residential Clean Energy Credit (Section 25D) was terminated by the One Big Beautiful Bill Act for expenditures after December 31, 2025. Cash and loan purchases in 2026 get no federal credit, and any pre-2026 carryforward is the only 25D activity left on a return.
Leases and PPAs are different. A company that owns the system on your roof may claim the Section 48E business credit if construction began by July 4, 2026, or the system is placed in service by December 31, 2027. Whether that lowers your payment depends on the contract, so compare the lease or PPA rate against the cost of owning.
State credits and utility programs still exist. New York, for example, offers a state credit of 25% of qualified costs, capped at $5,000. Check your state energy office and utility for current programs, since they change often.
💰 System Cost
What Does an 8.4 kW System Cost and Pay Back in 2026?
EnergySage reports that systems average about $2.60 per watt before incentives, though individual quotes vary by installer, equipment, roof, and state. For a 21-panel, 8.4 kW system:
Cost before incentives: 8,400 W × $2.60 = $21,840
Federal credit for a purchased system: none in 2026
Year-1 production: about 11,000 kWh, roughly 100% of average use
Year-1 savings: 10,791 kWh × $0.183 = about $1,975, using EIA’s July 2026 national residential average of 18.3¢/kWh
That gives a simple payback of about 11 years at flat electricity prices, or about 10 years if rates rise 3% a year. The model assumes full retail-rate net metering, 0.5% yearly panel degradation, and a system that offsets all of the home’s usage.
Data visualization
Modeled cumulative cash flow for an 8.4 kW system bought for $21,840. Assumes 11,038 kWh in year 1, 0.5% yearly degradation, savings capped at 10,791 kWh of use at 18.3¢/kWh, with rates flat or rising 3% a year. Excludes financing, inverter replacement, maintenance, and state incentives. Source: author model using EIA and EnergySage inputs.
Chart summary: Under flat rates the system breaks even in year 12 of the chart (about 11.1 years) and nets about $25,600 by year 25. If rates climb 3% a year, break-even moves to about year 10 and the 25-year net rises to about $46,900. The result is sensitive to your utility rate and export credit rules, so rerun it with your numbers in the solar payback calculator.
Resale value. A Lawrence Berkeley National Laboratory study of home sales through 2013 found buyers paid about $4 per watt more for homes with owned solar, about $15,000 for a typical 3.6 kW system. The authors noted that premiums for any individual home depend on the market and are likely smaller as installed prices fall, so don’t count on resale value in your payback math.
Net metering matters. Some states, including California, now credit exported power well below the retail rate, which lengthens payback for systems sized to export a lot. Confirm your utility’s current rules before choosing a system size.
Solar vs utility company · 25-year comparison
25-year totals: 3%/yr rate increases, 0.5%/yr degradation, no federal credit. Methodology
Direct answers for US homeowners — sized for a $125/month electric bill.
About 12 to 29 panels, or 4.8 to 11.6 kW with 400 W panels. The range depends on how much of the roof is usable. NREL found that about 26% of the total roof area on small buildings is suitable for solar, which is roughly 455 sq ft and about 21 panels on a 1,750 sq ft roof. A simple gable roof with one clear south-facing plane can reach the high end. A shaded or multi-section roof lands near the low end.
It depends on electricity use and sun hours, not on house size. The average U.S. residential customer uses about 10,791 kWh a year (EIA). At 4.5 peak sun hours, 400 W panels, and a 0.80 system derate, that is about 21 panels (8.4 kW). The same home needs about 15 panels at 6.5 sun hours and about 27 at 3.5 sun hours. Divide your own annual kWh by 365 × sun hours × panel kW × 0.80 for a closer estimate.
Not for systems you buy with cash or a loan. The 30% Residential Clean Energy Credit (Section 25D) ended for expenditures after December 31, 2025, under the One Big Beautiful Bill Act. Companies that own leased or PPA systems may still claim a business credit under Section 48E if construction began by July 4, 2026, or the system is placed in service by December 31, 2027. Whether any of that value reaches you depends on the contract. Some states still offer credits, such as New York's 25% credit capped at $5,000.
At about $2.60 per watt before incentives (EnergySage marketplace average), an 8.4 kW system costs about $21,840. With full retail net metering and 18.3 cents per kWh, year-one savings are about $1,975, so simple payback is about 11 years at flat electricity prices, or about 10 years if rates rise 3% a year. Your result depends on your utility rate, export credit rules, sun hours, quote price, and any state incentive.
Yes, with lower output. East- or west-facing panels typically produce roughly 10% to 20% less per year than south-facing panels in the continental U.S. Southeast and southwest faces lose less. If your best plane faces east or west, plan for a few more panels to reach the same annual kWh, and check whether your roof has room. NREL's PVWatts calculator can model your exact roof direction and tilt.
Same usage, bill-based guide
Your 1,750 sq ft Roof 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.