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 home using 30 kWh per day needs about 8.3 kW of solar, roughly 21 panels rated 400W, at the commonly used planning figure of 4.5 peak sun hours. Depending on where you live, that can be as few as 16 panels or as many as 27. In 2026 the system costs about $21,700 before incentives, and the 30% federal tax credit is no longer available if you buy with cash or a loan.
For context, the typical US household uses roughly 860 to 870 kWh a month, or about 28 kWh a day, according to EIA residential data. A 30 kWh/day home (about 900 kWh a month) is therefore close to average, only slightly above it. At about 18 cents per kWh, that usage is a bill of roughly $164 a month.
Last reviewed October 3, 2026. Prices and tax rules change; confirm current figures before you sign a contract.
Quick answer for 30 kWh/day
Item
Typical value (4.5 peak sun hours)
System size
About 8.3 kW
Panels (400W)
About 21
Roof space
About 360–460 sq ft
Cost before incentives (~$2.60/W)
About $21,700
Federal tax credit (cash or loan)
None for 2026 installs
Simple payback at 18¢/kWh
11.3 years (9.8 with 3% yearly rate growth)
⚡ System Size
How Many Solar Panels Do You Need for 30 kWh/Day?
The sizing formula divides your daily usage by your location’s average peak sun hours, then adjusts for system losses (inverter, wiring, heat) of about 20%.
Formula: System size (kW) = Daily kWh ÷ Peak Sun Hours ÷ 0.80
At 4.5 peak sun hours: 30 ÷ 4.5 ÷ 0.80 = 8.3 kW. Installers often add a margin for shading, roof angle and future usage, so your quote may be somewhat larger. Peak sun hours range from about 3.5 in coastal Washington and Oregon to about 6 or more in the desert Southwest, according to NREL-based data. New England and the Great Lakes states sit toward the low end, and Arizona, Nevada and New Mexico at the top.
Panels needed for 30 kWh/day by peak sun hours
Peak sun hours
System size
Panels at 400W
Panels at 450W
3.5 (cloudy/northern)
10.7 kW
27
24
4.0
9.4 kW
24
21
4.5 (planning average)
8.3 kW
21
19
5.0
7.5 kW
19
17
5.5
6.8 kW
18
16
6.0 (desert Southwest)
6.3 kW
16
14
Data visualization
Panels needed for 30 kWh/day range from 16 to 27 depending on sun. Calculated at 80% system efficiency, counts rounded up. Source: formula above with NREL-based peak sun hours, 2026.
Chart summary: Sunlight changes the panel count more than anything else. A home in a 3.5-sun-hour area needs about 27 panels of 400W, while the same home at 6.0 sun hours needs about 16, a difference of roughly 40%. Higher-wattage panels cut the count by two to three panels but do not change the total kW you need.
Production also varies by season. Winter output can run well below the yearly average, so most homes rely on utility credits or the grid for part of the year. Shade, roof direction and tilt can all lower output. NREL’s PVWatts calculator lets you enter your address and system size to see projected monthly and annual production before you sign anything.
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 Cost
What Does a Solar System for 30 kWh/Day Cost in 2026?
EnergySage marketplace data puts the average residential quote at about $2.60 per watt before incentives in 2026. Other sources report national averages anywhere from about $2.40 to $3.34 per watt, and most homeowners pay between $2.50 and $3.50 per watt. Panels make up only about 12% of the total price, according to EnergySage. The rest is inverters, labor, permitting, hardware and installer overhead.
Estimated gross cost for 30 kWh/day, by sun hours (nearest $100)
Peak sun hours
System size
At $2.50/W
At $2.60/W (EnergySage average)
At $3.50/W
3.5
10.7 kW
$26,800
$27,900
$37,500
4.0
9.4 kW
$23,400
$24,400
$32,800
4.5
8.3 kW
$20,800
$21,700
$29,200
5.0
7.5 kW
$18,800
$19,500
$26,300
5.5
6.8 kW
$17,000
$17,700
$23,900
6.0
6.3 kW
$15,600
$16,300
$21,900
These are simple multiplications of system size by cost per watt. Real quotes also depend on roof type, electrical upgrades, equipment brand and local labor costs, and larger systems often cost slightly less per watt. Get at least three quotes and compare them by cost per watt, not just the total.
For homeowners who buy a system with cash or a loan, no. The Residential Clean Energy Credit (Section 25D), which paid 30% of system cost, ended for expenditures made after December 31, 2025, under the One Big Beautiful Bill Act signed in July 2025. The IRS Residential Clean Energy Credit page states that the credit does not apply to property placed in service after that date. The same ending applies to owned battery storage.
What this means for a 30 kWh/day home:
A system installed in 2026 gets no 25D credit, so the prices in this guide are close to what you actually pay. Do not subtract 30% unless a contractor shows you a written, legally valid basis.
If your system was installed and operating by December 31, 2025, you can still claim the credit on your 2025 return using IRS Form 5695.
Solar leases and power purchase agreements (PPAs) are owned by a third party, which may still qualify for business tax credits under a separate and shorter schedule. Some providers pass part of that value to you as lower monthly rates, but it is not guaranteed, so compare the contract terms carefully.
Some states, utilities and local governments offer their own incentives, such as rebates, property-tax exemptions or sales-tax exemptions. The DSIRE database lists current programs by state.
If you see an ad promising “30% federal tax credit through 2032” for a new 2026 purchase, treat it as outdated information and ask the installer to put the incentive in writing.
⚡ System Size
How Long Is the Solar Payback for a 30 kWh/Day Home?
Payback is the cost of the system divided by what it saves each year. A system sized for 30 kWh/day produces about 10,950 kWh a year (30 × 365). At the US average residential price of roughly 18 cents per kWh, as reported by EIA, that is about $1,971 of avoided electricity cost in year one. On the $21,700 system above, simple payback works out to 11.3 years with flat rates or 9.8 years if rates rise 3% a year (panel output is reduced 0.5% a year in both cases).
Your electricity price matters most. State averages in EIA data range from the low teens to over 40 cents per kWh, with Hawaii the highest and the Northeast generally well above the national average.
Data visualization
Payback for an $21,700 system runs from 5 to 17 years depending on electricity price. Assumes 30 kWh/day offset at retail rates, 0.5% yearly degradation, no incentives. Source: EIA 2026 rates, EnergySage 2026 pricing.
Chart summary: Payback falls steeply as electricity gets more expensive. At 12 cents per kWh the system takes 14 to 17 years to pay back, at the 18-cent national average about 10 to 11 years, and at 30 cents about 6 to 7 years. Rate growth speeds up payback in every case, but the effect is modest compared with the price you pay today.
Sun hours and cost per watt also change the result. The next table holds the rate at 18 cents and the price at $2.60 per watt, and changes only the sunlight.
Peak sun hours
System cost
Payback, flat rates
Payback, 3% growth
3.5
$27,900
14.6 years
12.3 years
4.0
$24,400
12.7 years
10.9 years
4.5
$21,700
11.3 years
9.8 years
5.0
$19,500
10.1 years
9.0 years
5.5
$17,700
9.2 years
8.2 years
6.0
$16,300
8.4 years
7.6 years
Sunnier locations need a smaller, cheaper system for the same 30 kWh/day, so they pay back sooner at the same electricity price. Cloudy regions with expensive electricity, such as parts of the Northeast, can still do well because of the higher price per kWh.
One more factor is how your utility credits power you send to the grid. Net metering rules differ by state and utility. Where exported power is credited below the retail rate, savings drop unless you use more of your solar output at home. Check your utility’s current policy before relying on the numbers here.
⚡ System Size
Is Solar Worth It for a 30 kWh/Day Home? (25-Year Math)
For many homeowners it is, but the margin depends on your electricity rate and how long you will stay in the home. Using the same assumptions as above (8.3 kW system, $21,700, 18¢/kWh, 0.5% yearly degradation, no incentives), the system avoids about $46,400 of electricity purchases over 25 years at flat rates, for a net gain of about $24,800 after the purchase price. If rates rise 3% a year, the net gain grows to about $45,500.
Data visualization
Cumulative cash flow reaches +$24,800 by year 25 at flat 18¢/kWh rates. Cash purchase, no federal credit, 0.5% yearly degradation, excludes maintenance and inverter replacement. Source: EIA 2026 rates, EnergySage 2026 pricing.
Chart summary: With flat rates the system breaks even around year 11 and reaches about $24,800 in net savings by year 25. With 3% yearly rate growth it breaks even around year 10 and reaches about $45,500. The true result for you will likely fall between the two lines, and it moves up in high-rate states and down in low-rate ones.
What these numbers leave out: loan interest if you finance, routine maintenance, an inverter replacement (inverters often wear out before panels), roof work, home insurance changes, and any state incentives or battery costs. A battery adds cost and backup power but is not required for the savings shown. If you plan to move within a few years, ask installers how the system affects resale value in your market.
Run your own scenario with our solar ROI calculator using your utility rate and local sun hours.
How We Calculated These Numbers
All figures in this guide come from simple, repeatable formulas, not from a single installation:
System size: daily kWh ÷ peak sun hours ÷ 0.80 (system efficiency).
Panel count: system size ÷ panel wattage, rounded up.
Cost: system size × cost per watt ($2.50, $2.60 or $3.50), before incentives.
Savings: 30 kWh × 365 days = 10,950 kWh a year, valued at 18¢/kWh in year one, reduced 0.5% a year for panel degradation (a commonly used planning figure) and, where stated, increased 3% a year for rate growth.
Payback: the year in which cumulative savings equal the system cost.
Assumptions to keep in mind: full-retail credit for all solar output, no financing cost, no incentives. Real systems vary with roof orientation, shading, equipment and local rules. This guide is for general information and is not financial, tax or legal advice; confirm tax treatment with a qualified tax professional.
Direct answers for US homeowners — sized for a $164/month electric bill.
About 21 panels rated 400W (an 8.3 kW system) at the common planning figure of 4.5 peak sun hours. In very sunny areas with 6 peak sun hours you need about 16 panels. In cloudier areas with 3.5 peak sun hours you need about 27. With 450W panels, subtract roughly two to three panels. Check your own sun hours in NREL's PVWatts.
Between 6.3 kW and 10.7 kW, with about 8.3 kW typical. The formula is daily kWh divided by peak sun hours divided by 0.80, which allows for inverter, wiring and heat losses. A typical panel covers roughly 17 to 22 square feet, so a 21-panel system needs about 360 to 460 square feet of usable, mostly unshaded roof.
About $21,700 for an 8.3 kW system at the 2026 average quote of roughly $2.60 per watt, before any incentives. Most homeowners land between $2.50 and $3.50 per watt, which puts this system between about $20,800 and $29,200. Larger systems usually cost less per watt, and prices vary by state, roof and equipment.
Not if you buy the system with cash or a loan. The Residential Clean Energy Credit (Section 25D) ended for expenditures made after December 31, 2025. Lease and PPA providers may still receive federal credits and pass some value to you, but that is not guaranteed. Check state, local and utility incentives in the DSIRE database.
About 11 years at the national average rate of roughly 18 cents per kWh with no rate increases, or about 10 years if rates rise 3% a year. At 30 cents per kWh it drops to about 6 to 7 years, and at 12 cents it stretches to about 14 to 17 years. Your electricity rate matters more than almost any other factor.
Same usage, bill-based guide
Your 30 kWh/Day 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.