Scenario: a 900 sq ft house (about 405 kWh a month on the square-footage proxy). 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 900 sq ft house typically needs about 9 solar panels (roughly 3.6 kW of 400 W panels) to cover the roughly 405 kWh of monthly electricity use that this site’s square-footage proxy assigns it, at 4.5 peak sun hours per day. In 2026 that system costs about $10,800 before state incentives, because the 30% federal tax credit no longer applies to solar you buy with cash or a loan. Square footage is only a stand-in for usage: your exact number depends on your own monthly kWh, your local sun hours, and your panel wattage.
Last updated October 6, 2026. Prices, rates and tax rules below reflect the site’s data as of that date; see Sources and method.
⚡ System Size
How Many Solar Panels Does a 900 sq ft House Need?
Home size is only a rough guide to electricity use. The U.S. Energy Information Administration (EIA) reports that the average American home used about 899 kWh per month (EIA, average US residential customer electricity use, 2022 (about 899 kWh per month)), and the average U.S. home is much larger than 900 sq ft. This site scales that usage by floor area (about 0.45 kWh per sq ft per month), which gives about 405 kWh a month for 900 sq ft. Real small houses land well above or below that: heat pumps, electric resistance heating, air conditioning and EV charging can push a small house far higher. Use your last 12 months of utility bills, not the square footage, to size a system.
Use this sizing formula:
System size (kW) = monthly kWh × 12 ÷ (peak sun hours × 365 × 0.82)
The 0.82 factor accounts for typical system losses (inverter, wiring, temperature, soiling), in line with the default assumptions in NREL’s PVWatts calculator. Then divide by the panel wattage:
Panels = system size (kW) × 1,000 ÷ panel watts
Worked example: at the proxy usage of 405 kWh/month and 4.5 sun hours, the system is 3.6 kW, or 9 panels of 400 W. Panels used for new rooftop installs today are commonly around 400 W, and each is roughly 20 sq ft, so even the highest count below needs only about 220 sq ft of usable roof.
Panels needed by usage (proxy usage at 70%, 100% and 130%)
Usage
Monthly kWh
System size
Panels (400 W)
Cost at $3.00/W
70% of proxy (efficient)
283
2.5 kW
7
$7,600
100% of proxy
405
3.6 kW
9
$10,800
130% (AC, electric heat, EV)
526
4.7 kW
12
$14,100
Calculated, not measured: 4.5 peak sun hours, 82% system efficiency, 400 W panels rounded up. The 70% and 130% rows show how far real usage can sit from the square-footage guess.
Data visualization
Panels needed by usage and sun hours. At the proxy usage of about 405 kWh/month a 900 sq ft house needs 9 panels (3.6 kW) at 4.5 sun hours. Source: NREL PVWatts loss assumptions; Green Energy Calculators formula.
Chart summary: Sun hours matter as much as usage. The proxy-usage house needs about 7 panels in a sunny region, 9 at the national average, and 11 in a low-sun region. Panel count scales with usage at any sun level. If your roof cannot fit the count, a smaller system that offsets part of your bill still saves money.
Roof direction and shade also change the result. East- or west-facing roofs typically produce somewhat less than south-facing roofs, and shading can cut output sharply unless you use microinverters or power optimizers. NREL’s free PVWatts calculator estimates production for your exact address, tilt and direction. You can also use our solar system size calculator with your utility bill.
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💰 System Cost
What Does Solar Cost for a 900 sq ft House in 2026?
This site models residential solar at $3.00 per watt before incentives, which puts the 3.6 kW system at about $10,800. Individual quotes vary: EnergySage’s marketplace data reports average quotes near $2.60 per watt in 2026, while full-market installer quotes run higher. Small systems often cost more per watt than large ones.
Estimated installed cost for a small-house system (calculated at $3.00/W)
System size
Approx. panels (400 W)
Installed cost
3.5 kW
9
$10,500
3.6 kW (this scenario)
9
$10,800
5 kW
13
$15,000
The 30% federal tax credit no longer applies to owned systems. The One Big Beautiful Bill Act, signed July 4, 2025, ended the Section 25D residential credit for expenditures after December 31, 2025. The IRS Residential Clean Energy Credit page states it is not available for property placed in service after that date. Many older cost guides still subtract 30%, which overstates your savings. State and local incentives (rebates, property tax exemptions, sales tax exemptions, production incentives) still vary widely, so check the DSIRE database for your area.
Quotes vary with roof complexity, equipment, permitting and installer margin, so get at least three and compare them by price per watt. Our solar tax credit calculator explains which incentives may still apply.
Solar vs utility company · 25-year comparison
25-year totals for a 900 sq ft house (about 405 kWh a month on the square-footage proxy): 3%/yr rate increases, 0.5%/yr degradation, no federal credit. Methodology
How Long Does Solar Take to Pay Off on a 900 sq ft House?
Simple payback is system cost divided by yearly bill savings. The 3.6 kW system produces about 4,855 kWh a year in this model. At the 18.19¢ U.S. average residential rate (EIA Electric Power Monthly, Table 5.6.B (year-to-date through July 2026), residential average retail price) and with 75% of the bill offset in year 1 (fixed charges and export-credit rules keep it below 100%), year-1 savings are about $662, so simple payback is roughly 16.3 years without the federal credit, or about 13.9 years once 3% yearly rate increases are counted.
Data visualization
Simple payback by state electricity rate, 3.6 kW system, no federal credit. At the 18.19¢/kWh US average, payback is about 16.3 years. Each state uses its own rate, sun hours and net-metering category from the site’s data file. Source: EIA, July 2026 year-to-date rates; Green Energy Calculators model.
Chart summary: Your electricity rate and your utility’s export policy are the biggest drivers of payback. In the model, payback runs about 16.5 years in Nevada, 16.3 at the national average and 9.1 in New York. These figures use the model’s yearly rate increase and panel degradation of 0.5% per year, and they exclude any inverter replacement; they overstate savings if your utility credits exports below the retail rate.
Over 25 years, this model puts total electricity spending without solar at about $32,200 and with solar (system cost plus the utility bills you still pay) at about $20,400, a net gain of roughly $11,800 before any state incentives.
Data visualization
Modeled cumulative cash flow, 3.6 kW system, years 0 to 25. Breaks even after about 13.9 years with rate increases and reaches about $11,800 by year 25. Source: EIA July 2026 rate; Green Energy Calculators model with 3% yearly rate growth.
Chart summary: The line starts at the system cost and rises each year as bill savings accumulate, crossing zero at the payback point. If your utility raises rates faster than modeled, breakeven arrives sooner.
Net metering rules can change this a lot. Where your utility credits exports at the full retail rate, the estimates above hold more closely. Where exports earn much less, as in California under NEM 3.0 (in effect since April 2023), you save the most by using solar power in your home during the day, and payback runs longer. Use our solar payback calculator or net metering calculator for your utility.
⚡ System Size
Does Location Change the Panel Count and Payback?
Yes, in two ways. Sun hours change how many panels you need, and your electricity rate changes how fast they pay off. EnergySage notes that a 5 kW system in Phoenix produces about 35% more electricity than the same system in Boston, which is why a sunnier location needs fewer panels for the same bill.
Payback for a 900 sq ft house by state (July 2026 EIA year-to-date residential rates)
Location
Avg. residential rate
Sun hours
Panels
Year-1 savings
Simple payback
Nevada
13.53¢/kWh
6.4
7
$460
16.5 years
Texas
16.06¢/kWh
5.6
8
$430
20.3 years
U.S. average
18.19¢/kWh
4.5
9
$660
16.3 years
New York
29.38¢/kWh
4.3
10
$1,240
9.1 years
California
33.25¢/kWh
5.8
7
$970
8.7 years
Each row uses that state’s rate, approximate sun hours and net-metering category from the site’s data file, with the same proxy usage and $3.00/W. California’s longer payback reflects NEM 3.0, which pays less for exported power. Sun hours are approximate state averages, not address-level estimates.
Summary: High electricity prices, not just strong sun, make solar pay off fastest. Check your utility’s current rate, net metering or export policy, and local incentives before comparing quotes. Explore our state solar pages for California, Texas, New York and Massachusetts. For a smaller house, see also our guide for an 800 sq ft house.
📋 Key Insights
Cash vs Loan vs Lease: Is Solar Worth It in 2026?
Solar can still save money for many small-house owners, but with the homeowner credit gone, how you pay matters more.
Cash purchase: No interest and the simplest math, but no federal credit. Payback is the roughly 16.3 years shown above at average rates.
Solar loan: Illustrative math, not a quote: financing the $10,800 system at 7% APR over 12 years costs about $111 per month. At the U.S. average rate the system offsets about $55 per month in year 1, so you would pay more than you save until the loan ends. At higher rates savings get closer to the payment. Your actual APR, term and fees will differ.
Lease or PPA: The installer owns the system, so you have little or no upfront cost. Under current law, third-party owners can still claim a commercial federal credit for eligible projects, which may lower your rate, but leases and PPAs often include annual price escalators and can complicate selling your home. Compare the total cost per kWh over the whole term, not only the first-year payment.
Installed equipment also matters for long-run cost. Panels are commonly warrantied for 25 years, but string inverters typically need replacing after roughly 10 to 15 years, while microinverters are designed to last longer and can improve output on shaded roofs. Ask installers what is warrantied and for how long.
Compare cash, loan and lease scenarios with our solar ROI calculator. This article is general information, not financial or tax advice; consult a qualified professional about your situation.
Sources and Method
Sizing: annual kWh ÷ (peak sun hours × 365 × 0.82), rounded up to whole 400 W panels. The 0.82 system factor reflects typical loss assumptions in NREL’s PVWatts.
Usage: EIA, average US residential customer electricity use, 2022 (about 899 kWh per month); square-footage proxy of 0.45 kWh per sq ft per month is a site assumption. See How to use EIA data.
Rates: EIA Electric Power Monthly, Table 5.6.B (year-to-date through July 2026), residential average retail price (July 2026).
Costs: this site’s $3.00/W model price; EnergySage marketplace data reports lower average quotes (about $2.60/W in 2026). See the methodology.
Payback and 25-year figures are modeled from the inputs above (3% yearly rate increases, 0.5% annual degradation, 75% year-1 bill offset, no state incentives, no financing costs). Real results vary by site, utility and installer.
Related calculators
Free tools for US homeowners — instant results, all 50 states.
Direct answers for US homeowners — sized for a 900 sq ft home.
On this site's square-footage proxy, a 900 sq ft house uses about 405 kWh a month and needs roughly 3.6 kW, or about 9 panels of 400 W, at 4.5 peak sun hours. Sunnier locations need as few as 7 and cloudier ones about 11. Square footage is only a rough guide, so divide your own annual kWh by (sun hours × 365 × 0.82) for the real size.
Not for homeowners who buy. The 30% residential credit (Section 25D) ended for expenditures after December 31, 2025, under the One Big Beautiful Bill Act, so cash and loan purchases installed in 2026 get no federal credit. Some state and local incentives remain, and companies that own leased or PPA systems may still claim a commercial federal credit.
At this site's $3.00 per watt model price, a 3.6 kW system for a 900 sq ft house costs about $10,800 before incentives. EnergySage marketplace data reports lower average quotes, near $2.60 per watt in 2026, while full-market installer quotes run higher. Small systems often cost more per watt than large ones, so compare written quotes.
In our model, a 3.6 kW system at the 18.19¢ US average rate has a simple payback of about 16.3 years, or about 13.9 years once yearly rate increases are counted. New York's rate gives about 9.1 years and Texas about 20.3 years. Weaker export credits lengthen payback.
Buying avoids lease escalators and keeps all the savings, but you no longer get a federal credit and the upfront cost is yours. Leases and PPAs can still benefit from a commercial credit claimed by the owner, which may lower your rate, though contract terms, escalators and home-sale complications vary. Compare cost per kWh over the full term.
900 sq ft home — solar by state
Panel count and payback vary by electricity rate and peak sun hours in your state.
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: 900 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.