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
Short answer: to offset 900 kWh per month, most US homes need about 15 to 25 solar panels (400 W each), which is a 5.8–9.9 kW system. The exact number depends mainly on your local sunshine. A typical mid-sun home needs a 7.5 kW system with 19 panels. At 2026 prices of roughly $2.50–$3.50 per watt, that system costs about $18,750–$26,250 before incentives, and the 30% federal residential tax credit no longer applies to systems installed in 2026.
900 kWh per month is close to what an average US home buys from the grid. EIA reported about 899 kWh per month (10,791 kWh per year) for 2022, and its more recent annual figures are somewhat lower, around 865 kWh per month for 2024. At the roughly 18¢ per kWh national average residential rate in mid-2026, 900 kWh costs about $165 per month.
Updated September 29, 2026. This guide now reflects the end of the federal Section 25D residential solar credit for 2026 installations, current EIA electricity prices, and 2026 installed-cost ranges. Cost and payback figures are calculated estimates, not quotes.
⚡ System Size
How Many Panels Do You Need to Offset 900 kWh per Month?
Use this formula: System size (kW) = Monthly kWh ÷ (Peak sun hours per day × 30 days × 0.80 system factor).
Peak sun hours are the equivalent number of hours per day at full-strength sunlight (1,000 W/m²). The 0.80 factor is a conservative planning allowance for inverter losses, wiring, dirt, heat, and shading. For reference, NREL’s PVWatts calculator uses a default of 14% system losses plus a separate 96% inverter efficiency, which works out to a similar overall factor of roughly 0.82.
For a mid-sun city such as Dallas (about 5.0 peak sun hours): 900 ÷ (5.0 × 30 × 0.80) = 7.5 kW. At 400 W per panel, that is 19 panels.
Panels needed for 900 kWh/month by location (calculated, 400 W panels)
Location
Peak sun hours (rounded planning value)
System size needed
Panels (400 W)
Panels (440 W)
Phoenix, AZ
6.5
5.8 kW
15
14
Denver, CO
5.3
7.1 kW
18
17
Dallas, TX
5.0
7.5 kW
19
18
Atlanta, GA
4.7
8.0 kW
20
19
Chicago, IL
4.2
8.9 kW
23
21
Seattle, WA
3.8
9.9 kW
25
23
Sun-hour values are rounded planning figures. Your address, roof tilt, and shading will change them, so run your ZIP code through NREL PVWatts or our solar system size calculator before requesting quotes.
Data visualization
Panels needed for 900 kWh/month range from 15 in Phoenix to 25 in Seattle. Calculated with 400 W panels and a 0.80 system factor. Sun-hour inputs are rounded planning values; verify with NREL PVWatts.
Chart summary: Sunlight is the biggest driver of panel count. Seattle needs about 67% more panels than Phoenix (25 vs. 15) to produce the same 900 kWh per month. Most mid-sun cities land between 18 and 20 panels.
Run the numbers for your state
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💲 2026 Cost
What Does a Solar System for 900 kWh per Month Cost in 2026?
Most 900 kWh/month homes need a 6–9 kW system. Recent 2026 price guides put residential solar at roughly $2.50–$3.50 per watt installed before incentives, and this article uses $2.80/W as a planning value. Individual quotes can fall outside that range depending on state, roof, equipment, and installer.
System size
Low ($2.50/W)
Planning ($2.80/W)
High ($3.50/W)
6 kW
$15,000
$16,800
$21,000
7.5 kW
$18,750
$21,000
$26,250
9 kW
$22,500
$25,200
$31,500
These figures are before any incentives. For homeowner-owned systems installed in 2026 there is no federal residential credit to subtract (see the next section). Some states, utilities, and municipalities offer rebates, performance payments, or property-tax and sales-tax exemptions. Check the DSIRE database for programs in your area.
Data visualization
A 7.5 kW system costs about $21,000 at $2.80/W, within a $18,750–$26,250 range. Calculated as system size × installed price per watt, before any incentives.
Chart summary: Cost scales linearly with system size, but price per watt moves the total more than most homeowners expect. Moving from $2.50/W to $3.50/W adds about $7,500 to a 7.5 kW system, which is why comparing at least three quotes matters. To apply this credit correctly, start with a firm figure from our guide to How Much Do Solar Panels Cost in 2026?. For more on this topic, see our guide to How Many Solar Panels for 600 kWh/Month? 2026 Guide.
Solar vs utility company · 25-year comparison
25-year totals: 3%/yr rate increases, 0.5%/yr degradation, no federal credit. Methodology
Is the Federal Solar Tax Credit Still Available in 2026?
For homeowners who buy a system with cash or a loan, no. The 30% Residential Clean Energy Credit (Section 25D) was terminated by the 2025 federal budget law (the One Big Beautiful Bill Act) for expenditures made after December 31, 2025. The IRS treats the expenditure as made when installation is complete, so a system finished in 2026 does not qualify even if a deposit was paid in 2025.
What still exists:
Systems completed by December 31, 2025 can claim the 30% credit on the 2025 return (IRS Form 5695), with unused credit carrying forward.
Leased or PPA systems owned by a third party may still benefit from the commercial §48E credit, subject to construction-start and placed-in-service deadlines. Any benefit reaches you only through the provider’s pricing, so read the contract terms closely.
State and local incentives still exist in many places.
Tax rules can change, so verify current eligibility on the IRS Residential Clean Energy Credit page or with a tax professional. Because the 30% credit is gone for owned 2026 systems, the cost and payback figures in this guide do not subtract it.
📋 Key Insights
Worked Example: A 7.5 kW System for 900 kWh per Month
This is a calculated model, not a measured installation. It shows how the numbers connect using mid-sun (5.0 hours per day) assumptions.
18.3¢/kWh (approximate US residential average, mid-2026)
Year-1 bill avoided
10,800 kWh × $0.183 ≈ $1,976
Gross installed cost
7,500 W × $2.80 = $21,000
Federal credit
$0 (owned system installed in 2026)
The modeled output is within about 1.4% of the 10,800 kWh target. Sizing a few percent above your target is common because panel output declines slowly over time (a typical planning figure is about 0.5% per year) and real weather varies. The estimate also assumes every kWh produced offsets a kWh you would otherwise buy at the retail rate, which depends on your net-metering or export-credit policy.
📈 Payback
How Long Does a 900 kWh/Month Solar System Take to Pay Back?
For the 7.5 kW example above ($21,000, no tax credit, 18.3¢/kWh, 0.5% annual degradation, flat electricity prices), payback is about 10.9 years. If electricity prices rise 2.5% per year, payback improves to about 9.7 years.
Over 25 years, the same system avoids about $46,600 in electricity purchases in the flat-price case, for a net gain of about $25,600 after the $21,000 purchase. With 2.5% annual price increases, the net gain is about $42,200. These are model results and do not include maintenance, inverter replacement, financing costs, or changes in export-credit rules.
Data visualization
A $21,000 system breaks even in about 10.9 years at flat prices, or 9.7 years with 2.5% annual price increases. Cumulative net cash flow, 900 kWh/month offset at 18.3¢/kWh, 0.5% annual degradation, no tax credit.
Chart summary: Both lines cross zero between years 9 and 11, then the gap widens as electricity prices compound. By year 25 the flat-price case nets about $25,600 and the rising-price case about $42,200.
Payback depends heavily on what you pay per kWh. The table and chart below use the same $21,000 system, 900 kWh per month, and full retail-rate credit for all solar output.
Electricity price
Year-1 bill avoided
Payback (with 0.5%/yr degradation)
13¢/kWh (e.g., Nevada, lowest state in June 2026 EIA data)
$1,404
≈15.5 years
16¢/kWh (e.g., Texas, about 15.9¢)
$1,728
≈12.5 years
18.3¢/kWh (US average)
$1,976
≈10.9 years
25¢/kWh
$2,700
≈7.9 years
35¢/kWh (e.g., California, about 34.7¢)
$3,780
≈5.6 years
Data visualization
Payback ranges from about 5.6 years at 35¢/kWh to 15.5 years at 13¢/kWh. Same $21,000 system and 900 kWh/month offset; assumes solar output is credited at the full retail rate. Calculated, not quoted.
Chart summary: Your utility rate matters more than almost any other input. Homes paying 25¢/kWh or more see payback under 8 years in this model, while homes near 13¢ wait 15 years or more. High-rate states that have cut export credits (California is one example) can pay back more slowly than the retail-rate figure shows, so check your utility’s current export policy. Use our solar payback calculator to model your own numbers.
⚡ System Size
Does Panel Brand or Wattage Change How Many You Need?
Panel wattage changes how many panels you need, not how much electricity the system produces. A 7.5 kW system produces the same energy whether it uses 19 panels of 400 W or 17 panels of 440 W. Higher-wattage panels mainly help when roof space is limited.
Panel option
Panels for about 7.5 kW
Approx. array area*
400 W (common residential size)
19 (7.6 kW)
~340–400 sq ft
440 W (higher-output)
17 (7.48 kW)
~305–360 sq ft
*Assumes about 18–21 sq ft per panel; usable roof area also depends on setbacks and obstructions.
Roof direction also matters. East- and west-facing roofs typically produce less than a south-facing roof at the same tilt, and heavy shade can cut output further. Model your exact roof in PVWatts, then add panels if needed to reach your 900 kWh per month target.
For most homeowners with enough roof space, the number that moves payback is the installed price per watt, not the brand name. Compare quotes on a $/W basis and check warranties, inverter type, and installer reviews. Use our solar savings calculator to test your own numbers.
🔎 Sources
Methodology and Sources
Sizing formula: kW = monthly kWh ÷ (peak sun hours × 30 × 0.80). Panel counts are rounded up to whole 400 W (or 440 W) panels. Sun-hour inputs are rounded planning values; use NREL PVWatts for address-level estimates.
Electricity prices: approximate US residential average of 18.3¢/kWh and state examples from EIA Electric Power Monthly data for mid-2026. Your own rate may differ.
Installed cost: 2026 residential price guides commonly cite $2.50–$3.50 per watt before incentives; $2.80/W is used here as a planning value. Actual quotes vary.
Direct answers for US homeowners — sized for a $165/month electric bill.
Most US homes need 15–25 panels of 400 W, or a 5.8–9.9 kW system, depending on local sunlight. A mid-sun location such as Dallas (about 5.0 peak sun hours per day) needs a 7.5 kW system, which is 19 panels. Phoenix needs about 15 panels; Seattle needs about 25. Use kW = monthly kWh ÷ (sun hours × 30 × 0.80).
At $2.50–$3.50 per watt installed, a 6 kW system costs about $15,000–$21,000, a 7.5 kW system $18,750–$26,250, and a 9 kW system $22,500–$31,500 before incentives. The $2.80/W planning value gives about $21,000 for 7.5 kW. Quotes vary by state, roof complexity, equipment, and installer, so compare several.
Not for homeowner-owned systems installed in 2026. The Section 25D Residential Clean Energy Credit ended for expenditures made after December 31, 2025. Systems completed by that date can still claim 30% on the 2025 tax return. Leased or PPA systems may still benefit from the commercial §48E credit through the provider. Confirm details with a tax professional.
In the base case (7.5 kW, about $21,000, 18.3¢/kWh, 0.5% yearly degradation, no tax credit), payback is about 10.9 years, or about 9.7 years if rates rise 2.5% a year. It ranges from roughly 5.6 years at 35¢/kWh to 15.5 years at 13¢/kWh. Lower export credits lengthen payback.
Yes. East- or west-facing roofs typically produce less than south-facing roofs, so you may need more panels; model your exact roof in NREL PVWatts. Higher-wattage panels reduce the count without changing output: about 17 panels of 440 W match 19 panels of 400 W (roughly 7.5 kW).
Same usage, bill-based guide
Your 900 kWh/Month target maps to roughly a $150/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.