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: To offset 1,300 kWh per month, most US homes need about 25–34 solar panels (400W each), a 10–13.6 kW system, depending on local peak sun hours. At a national planning average of 4.5 peak sun hours per day, that is 31 panels (12.4 kW). In 2026 a system that size costs roughly $32,000–$42,000 before incentives, and no federal tax credit applies to systems you buy — the 30% Section 25D credit ended on December 31, 2025.
Last updated: October 3, 2026.
Using 1,300 kWh a month puts you about 45% above the typical US household, which the U.S. Energy Information Administration (EIA) puts at roughly 900 kWh per month (2022 data). Homes at this level often have a large floor plan, a pool, electric heating or an EV charger. Three variables decide your panel count: your location’s peak sun hours, the wattage of the panels you choose, and system losses (inverter, wiring, heat, soiling).
Key takeaways
Panel count scales almost inversely with sun hours: 21 panels at 6.5 hours, 39 at 3.5 hours.
Without the federal credit, a 12.4 kW system costs about $32,000–$42,000 depending on which price benchmark you use.
Payback depends mostly on your local electricity rate: about 5 years in Hawaii versus about 16 years in Louisiana under the same assumptions.
Always confirm with your own address in NREL’s PVWatts before signing a contract.
⚡ System Size
How Many Solar Panels Do You Need for 1,300 kWh per Month?
Use this formula, which includes a system efficiency factor of 0.80 (a conservative allowance for inverter, wiring and temperature losses):
Panels needed = Monthly kWh ÷ (Peak sun hours × 30 days × Panel kW × 0.80)
Worked examples with 400W (0.40 kW) panels:
Phoenix area (about 6.5 sun hours): 1,300 ÷ (6.5 × 30 × 0.40 × 0.80) = 20.8, so 21 panels
National planning average (4.5 sun hours): 1,300 ÷ (4.5 × 30 × 0.40 × 0.80) = 30.1, so 31 panels
Chicago area (about 4.2 sun hours): 1,300 ÷ (4.2 × 30 × 0.40 × 0.80) = 32.2, so 33 panels
Seattle area (about 3.5 sun hours): 1,300 ÷ (3.5 × 30 × 0.40 × 0.80) = 38.7, so 39 panels
That is a swing of 18 panels from geography alone. Round up to a whole panel; you cannot install 0.1 of one.
Panel count by peak sun hours (400W panels, 1,300 kWh/month):
Peak sun hours/day
Example regions (approximate)
System size
Panels
Est. cost at $2.60/W
Est. cost at $3.36/W
3.5
Seattle area
15.6 kW
39
$40,560
$52,416
4.0
Chicago, New York area (about 4.0–4.6)
13.6 kW
34
$35,360
$45,696
4.5
National planning average
12.4 kW
31
$32,240
$41,664
5.0
Atlanta area (about 4.8–5.1)
11.2 kW
28
$29,120
$37,632
5.5
Dallas, Denver area (about 5.1–5.6)
10.0 kW
25
$26,000
$33,600
6.0
Las Vegas, Albuquerque area (about 6.2)
9.2 kW
23
$23,920
$30,912
6.5
Phoenix area
8.4 kW
21
$21,840
$28,224
Sun-hour values for cities differ slightly between data sources and by ZIP code, so treat the regional examples as approximate. Enter your address in NREL’s PVWatts Calculator for your exact figure, or use our solar system size calculator.
Data visualization
21 to 39 panels cover 1,300 kWh/month, depending on peak sun hours. 400W panels, formula kWh ÷ (sun hours × 30 × 0.40 kW × 0.80), rounded up. Source: NREL PVWatts sun-hour ranges; Green Energy Calculators calculation.
Chart summary: The chart shows panel count falling steadily as sun exposure rises. A home with 3.5 peak sun hours needs 39 panels, while one with 6.5 hours needs 21, which is about 46% fewer. For most of the country (4.0 to 5.5 sun hours) the answer lands between 25 and 34 panels, with 31 panels as the national planning case.
How panel wattage changes the count (4.5 sun hours, 1,300 kWh/month):
Panel wattage
Panels needed
350W
35
400W
31
440W
28
Higher-wattage panels reduce the count and roof area needed, though per-panel prices are higher. Compare cost per watt, not cost per panel.
Run the numbers for your state
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⚡ System Size
What Does a Solar System for 1,300 kWh per Month Cost in 2026?
Published 2026 price benchmarks differ because they measure different things. EnergySage marketplace quotes average about $2.60 per watt before incentives (a typical quoted system is around 12 kW, with an average quote near $31,135), because homeowners compare competing bids. SEIA and Wood Mackenzie report a higher national residential average of about $3.36 per watt. Applying both to a 12.4 kW system:
Price benchmark
$ per watt
12.4 kW system (31 × 400W)
EnergySage marketplace quotes (2026)
$2.60
$32,240
SEIA / Wood Mackenzie national average (2026)
$3.36
$41,664
Costs also vary with roof complexity, panel and inverter brand, whether your electrical panel needs an upgrade, and local permitting. Because there is no federal credit for purchased systems in 2026, the quote you accept matters more than before. Get at least three quotes and compare them on a cost-per-watt basis.
Data visualization
A 12.4 kW system costs about $32,200 to $41,700 before incentives in 2026. Sizes are the 400W panel counts needed at 6.5 down to 3.5 peak sun hours; no federal credit applies to purchased systems. Source: EnergySage 2026 ($2.60/W); SEIA/Wood Mackenzie 2026 ($3.36/W).
Chart summary: Cost rises linearly with system size. A 12.4 kW system costs about $32,200 at the lower benchmark and $41,700 at the higher one, a gap of about $9,400 that comes from which price source you use. A 6.5-sun-hour home needs a system roughly $18,700 (at $2.60/W) to $24,200 (at $3.36/W) cheaper than a 3.5-sun-hour home.
Solar vs utility company · 25-year comparison
25-year totals: 3%/yr rate increases, 0.5%/yr degradation, no federal credit. Methodology
What Affects Output: Tilt, Orientation, Shading and Losses
The formula above is a sizing estimate. Four factors move real-world output:
Orientation and tilt. In the continental US, south-facing roofs generally produce the most annual energy. East- and west-facing roofs produce less, so you may need extra panels to hit the same 1,300 kWh, while heavily shaded or north-facing roofs are the hardest case.
Shading. Trees, chimneys and neighboring buildings can cut output sharply. Microinverters or power optimizers can reduce the impact on the rest of the array.
System losses. We use a 0.80 efficiency factor, which is deliberately conservative. NREL’s PVWatts tool uses a default total system loss of roughly 14% (a factor near 0.86), so a well-built system may outperform this guide’s estimate.
Seasons. Output is highest in summer and lowest in winter, so a system sized for 1,300 kWh as a monthly average will overproduce in some months and underproduce in others. Whether that surplus earns full retail credit depends on your utility’s net metering or net billing rules.
Because roofs vary so much, the most reliable step is to model yours. Enter your address, tilt and azimuth in PVWatts, then compare the annual result with your target of about 15,600 kWh (1,300 × 12). Our solar savings calculator can then turn that output into dollars at your local rate.
⚡ System Size
How Long Does It Take a 1,300 kWh Solar System to Pay for Itself?
Payback depends on two numbers: what you pay and what each kWh is worth. The EIA reports a 2025 US average residential rate of about 17.3¢/kWh (preliminary), up from 13.15¢ in 2020, with large state differences.
The table below uses a 12.4 kW system at $32,240 (the $2.60/W benchmark) producing 15,600 kWh per year, valued at each state’s 2025 average residential rate, with no incentives and no rate growth.
State
Avg. residential rate (2025)
Annual savings
Simple payback
Hawaii
40.59¢
$6,332
5.1 years
California
32.54¢
$5,076
6.4 years
Massachusetts
30.48¢
$4,755
6.8 years
New York
26.39¢
$4,117
7.8 years
US average
17.30¢
$2,699
11.9 years
Texas
15.47¢
$2,413
13.4 years
Florida
15.24¢
$2,377
13.6 years
Louisiana
12.57¢
$1,961
16.4 years
Rates: EIA 2025 annual residential averages. Payback = $32,240 ÷ annual savings. At the higher $3.36/W price benchmark ($41,664), every payback period is about 29% longer.
Three caveats matter. First, net metering rules change the result: California now credits exported power well below the retail rate under its net billing tariff, so real payback there can be longer than shown. Second, state incentives shorten payback: a New York buyer claiming the 25% state credit (capped at $5,000) would have a net cost near $27,240 and a payback of about 6.6 years. Third, the model excludes financing costs and a likely inverter replacement during the system’s life.
Data visualization
Simple payback runs from 5.1 years in Hawaii to 16.4 years in Louisiana. 12.4 kW system at $32,240 ($2.60/W); 15,600 kWh per year valued at each state 2025 average residential rate; 0% rate escalation; no incentives. Source: EIA 2025 retail rates; Green Energy Calculators calculation.
Chart summary: Electricity price is the dominant driver: Hawaii, California, Massachusetts and New York all pay back in under 8 years, while Texas, Florida and Louisiana take 13 to 16 years on the same system cost. The US average of 11.9 years sits near the middle. Bar colors run from green (fastest payback) to red (slowest).
The next chart tracks cumulative cash flow for the US-average case: $32,240 cost, $2,699 of first-year savings, 0.5% annual output decline (NREL’s analysis of field data found a median PV degradation rate near 0.5% per year), flat electricity rates, and no incentives.
Data visualization
The US-average system breaks even between year 12 and year 13 and nets about $31,300 by year 25. $32,240 cost; $2,699 first-year savings at 17.3¢/kWh; 0.5% annual degradation; 0% rate escalation; no federal credit, financing or inverter replacement. Source: EIA 2025 rates; NREL degradation study; Green Energy Calculators model.
Chart summary: Under these assumptions the cumulative line crosses zero between year 12 and year 13 and reaches about +$31,300 by year 25. The scenario uses 0% electricity price growth, which is conservative because the US average residential rate rose about 32% from 2020 to 2025 (EIA); an inverter replacement or financing interest would lower the result. Your own payback will differ with state incentives, net metering rules and installed price.
⚡ System Size
Is There Still a Federal Tax Credit for a 1,300 kWh Solar System?
For systems you buy, no. The 30% Residential Clean Energy Credit (Section 25D) ended for expenditures made after December 31, 2025 under the One Big Beautiful Bill Act (signed July 4, 2025). Installation must have been completed by that date, so a cash or loan purchase in 2026 receives no federal residential credit. Homeowner-owned battery storage lost the same credit.
What remains:
2025 installations. If your system was placed in service by December 31, 2025, you can still claim the credit on your 2025 return (IRS Form 5695). Review the IRS rules for carryforward of any unused amount.
Leases and PPAs. Third-party-owned systems may still benefit from the commercial credit (Section 48E), with deadlines running through 2027, and the installer may pass some of that value on through lower rates. Compare total 25-year cost, not just the monthly payment, because you do not own the system.
State income tax credits. Three examples: New York offers 25% of system cost up to $5,000; Massachusetts offers 15% up to $1,000 (plus the SMART production incentive program); Arizona offers 25% up to $1,000. Other states have their own programs.
Tax exemptions. Several states, including Florida, exempt solar equipment from sales tax, and many states exempt added home value from property tax.
Utility programs and net metering. These vary by utility and change often.
Rules and amounts change, so confirm current programs for your address in the DSIRE database and with your installer before signing. Our solar tax credit calculator can help you add up whichever incentives apply to you.
Cost: system kW × $2.60/W (EnergySage 2026 marketplace average) and × $3.36/W (SEIA/Wood Mackenzie 2026 national average).
Savings and payback: 15,600 kWh per year × EIA 2025 average residential rate for each state; simple payback = cost ÷ first-year savings. The 25-year chart applies 0.5% annual degradation and flat rates.
Not included: incentives (except the one New York example), financing interest, maintenance, inverter replacement, and net metering limits.
These are planning estimates, not a quote or financial advice. Your results will differ with your roof, utility and installer.
Direct answers for US homeowners — sized for a $225/month electric bill.
Most US homes need about 25–34 panels of 400W each to offset 1,300 kWh per month, which is a 10–13.6 kW system. At the national planning average of 4.5 peak sun hours per day you need about 31 panels (12.4 kW). The count ranges from roughly 21 panels in a Phoenix-type climate (6.5 sun hours) to 39 in a Seattle-type climate (3.5 sun hours). Higher-wattage panels reduce the count: 440W panels need about 28 at 4.5 sun hours.
A 12.4 kW system sized for 1,300 kWh per month costs roughly $32,000–$42,000 before incentives in 2026. That range reflects about $2.60 per watt (EnergySage marketplace quotes) to $3.36 per watt (SEIA/Wood Mackenzie national benchmark). There is no federal tax credit for systems you buy and install in 2026, so state credits, utility programs and competing quotes matter more. Get at least three quotes.
No, not for systems you buy. The 30% Residential Clean Energy Credit (Section 25D) ended for expenditures made after December 31, 2025 under the One Big Beautiful Bill Act, so a cash or loan purchase in 2026 earns no federal credit. Homeowners whose systems were placed in service by December 31, 2025 can still claim it. Leased or PPA systems may still benefit indirectly through the commercial credit (Section 48E), with deadlines through 2027, and some states such as New York, Massachusetts and Arizona still offer their own credits.
At the 2025 US average residential rate of about 17.3¢/kWh, a 12.4 kW system costing $32,240 pays back in about 11.9 years on a simple basis, or about 12.3 years including 0.5% annual panel degradation. By state, simple payback runs from about 5.1 years in Hawaii (40.6¢/kWh) to about 16.4 years in Louisiana (12.6¢/kWh). These estimates value every kWh at the retail rate and exclude incentives, financing costs and inverter replacement.
Yes. In the US, south-facing roofs generally produce the most electricity; east- or west-facing roofs produce less, so you may need extra panels to cover the same 1,300 kWh. Shading can cut output sharply, which is why installers model your roof before quoting. You can test your own roof for free in NREL's PVWatts calculator by entering your address, tilt and azimuth, then compare the result to your 15,600 kWh annual target.
Same usage, bill-based guide
Your 1,300 kWh/Month target maps to roughly a $200/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.