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
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Quick answer: Most modular homes need about 11 to 25 solar panels (400 W each), a 4.4 kW to 10.0 kW system, to cover their yearly electricity use. A typical home with a $125 monthly electric bill needs about 15 panels (6.0 kW), which costs roughly $20,160 installed in 2026. Updated October 1, 2026: the 30% federal homeowner tax credit ended on December 31, 2025, so older guides that quote a 30% discount no longer apply to systems you buy now.
Three inputs set your number: your annual electricity use in kWh, your location’s peak sun hours, and the wattage of the panels you choose. This guide shows the formula, 2026 cost benchmarks, how location changes the count, and how long payback takes without the federal credit. Every table and chart below is calculated from the stated assumptions, not copied from an installer quote.
📋 Key Insights
Can a Modular Home Have Solar Panels?
In most cases, yes. A modular home is built in sections in a factory, then set on a permanent foundation, and it follows the same state and local building codes as a site-built home. That makes standard roof-mounted solar workable for most modular homes.
Do not confuse modular with manufactured (HUD-code) housing. Manufactured homes are built to a federal code and are a different category, so ask your installer to confirm the roof structure is suitable and check your home’s warranty before any roof penetration. Rural lots also deserve a shade check, since trees can cut output.
⚡ System Size
How to Calculate Solar Panel Count for a Modular Home
The formula has three steps and needs no contractor quote.
Step 1: Find your annual kWh use. Add up 12 months of electric bills. For comparison, the U.S. Energy Information Administration (EIA) reports that the average U.S. residential customer used 10,791 kWh in 2022, about 899 kWh a month.
Step 2: Look up your peak sun hours. NREL’s PVWatts calculator gives address-level solar data. Many U.S. locations fall between roughly 3.5 and 6.5 peak sun hours a day, and 4.5 is a reasonable national midpoint.
Step 3: Apply the formula. Required system size in kW = annual kWh ÷ (peak sun hours × 365 × 0.86). The 0.86 factor accounts for typical system losses from wiring, inverter conversion, heat and dirt (PVWatts uses about 14% by default). Then divide by your panel’s kW rating (0.4 kW for a 400 W panel) and round up.
Example, $125 monthly bill: $125 ÷ $0.1834 per kWh ≈ 682 kWh a month, or about 8,180 kWh a year. At 4.5 sun hours, 8,180 ÷ (4.5 × 365 × 0.86) = 5.79 kW, and 5.79 ÷ 0.4 = 14.5, which rounds up to 15 panels (6.0 kW).
The table applies the same method to four usage levels. Costs use the $3.36 per watt national benchmark and savings use 18.34 cents per kWh.
Panels Needed by Annual Electricity Use (4.5 Peak Sun Hours)
Annual use
Monthly bill at 18.34¢
System size
Panels (400 W)
Gross cost at $3.36/W
Bill avoided per year
Simple payback
6,000 kWh
$92
4.4 kW
11
$14,784
$1,100
13.4 yrs
8,180 kWh
$125
6.0 kW
15
$20,160
$1,500
13.4 yrs
10,791 kWh
$165
8.0 kW
20
$26,880
$1,979
13.6 yrs
14,000 kWh
$214
10.0 kW
25
$33,600
$2,568
13.1 yrs
Simple payback is gross cost divided by first-year bill avoided, with no incentives, financing or rate changes.
Solar panels needed by annual electricity use. A home at the 10,791 kWh national average needs 20 panels of 400 W at 4.5 peak sun hours. Source: EIA household use, NREL PVWatts method, 2026.
Chart summary: Panel count scales almost linearly with electricity use. At 4.5 peak sun hours, a home using 6,000 kWh/year needs about 11 panels, a home at the 10,791 kWh national average needs about 20, and a 14,000 kWh home needs about 25. For more on this topic, see our guide to How Many Solar Panels for a Vacation Home?.
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💰 System Cost
Modular Home Solar Cost in 2026 and Incentives That Still Exist
SEIA and Wood Mackenzie put the national average residential system price at $3.36 per watt in Q3 2026, down 1.4% from a year earlier (SEIA Solar Market Insight Q3 2026). Quotes vary by installer, roof and region, so treat this as a benchmark. At that price a 6.0 kW system costs about $20,160, and a 10 kW system about $33,600.
The federal credit has ended for buyers. The One Big Beautiful Bill Act, signed July 4, 2025, ended the Section 25D Residential Clean Energy Credit for expenses made after December 31, 2025. Under IRS rules the expense counts when installation is complete, so a system finished in 2026 or later does not qualify. Homeowners who finished installation in 2025 can still claim the credit, including carryforward of unused amounts. Companies that own leased or power-purchase-agreement systems may still use a business credit, which can show up in lease pricing, so compare any lease offer carefully. See the IRS Residential Clean Energy Credit page for the rules.
State and utility incentives still matter. New York, for example, offers a state tax credit of 25% of system cost up to $5,000. Search your state in DSIRE, the database of state incentives, before you decide.
Extra costs to ask about. Quotes can differ because of roof work, electrical panel upgrades, and microinverters or optimizers for shaded roofs. Ask each installer to itemize these so you can compare quotes fairly.
Takeaway: In 2026 the main cost lever you control is the quote itself. Get at least three itemized quotes, and check state incentives, because there is no federal credit to offset the price.
Solar vs utility company · 25-year comparison
25-year totals: 3%/yr rate increases, 0.5%/yr degradation, no federal credit. Methodology
How Peak Sun Hours Change Your Modular Home Panel Count
Location is the biggest variable after your electricity use. The table holds the home constant at 8,180 kWh a year and changes only the sun. Sun-hour values are rounded annual averages from NREL-based data and vary by site, tilt, orientation and shade.
Panels Needed for 8,180 kWh a Year by Location
Location
Peak sun hours/day
System size needed
Panels (400 W)
Gross cost at $3.36/W
Phoenix, AZ
6.5
4.0 kW
11
$14,784
Miami, FL
5.5
4.7 kW
12
$16,128
U.S. average
4.5
5.8 kW
15
$20,160
Detroit, MI
4.0
6.5 kW
17
$22,848
Seattle, WA
3.5
7.4 kW
19
$25,536
Data visualization
Panels needed for the same 8,180 kWh home by location. Phoenix needs 11 panels and Seattle needs 19 at 400 W each. Source: NREL PVWatts sun-hour averages, EIA usage method, 2026.
Chart summary: Sunshine moves the count more than anything else. The same 8,180 kWh home needs 11 panels in Phoenix but 19 in Seattle, roughly 73% more, because Seattle gets about 3.5 peak sun hours a day against about 6.5 in Phoenix.
Roof shape and shading also matter on rural modular lots. A south-facing roof with a moderate pitch is ideal, and nearby trees can cut output. Microinverters or optimizers can reduce shading losses, so ask installers to show a shade analysis in their proposal.
📋 Key Insights
Grid-Tied vs. Off-Grid Solar for a Modular Home
Most modular homes have utility service, which makes a grid-tied system the usual choice. It sends surplus power to the grid and draws from the grid at night, so you do not need batteries to cover nighttime use.
How much you are paid for exports depends on your state and utility. Some places credit exports at or near the retail rate, while others, such as California since 2023, use net billing with lower export credits. Ask your utility or installer for the current tariff in writing, because it directly changes your payback.
Off-grid solar needs enough panels and batteries to carry the home through nights and cloudy stretches, plus often a backup generator. It can make sense where the utility cannot connect the home at a reasonable cost, such as a remote lot. Ask the utility for a written line-extension quote before choosing. For small off-grid or cabin setups, see these solar kits from Shop Solar Kits† (affiliate link; code WAYSENG101 at checkout).
How Long Until Solar Pays for Itself on a Modular Home?
For the 15-panel, 6.0 kW system above, with a $125 monthly bill avoided at today’s 18.34 cents per kWh, simple payback is about 13.5 years with no incentives and about 10.1 years if a $5,000 state credit applies. The 18.34 cents figure is the EIA’s June 2026 national residential average, which was up 5.0% from a year earlier (EIA Electric Power Monthly). The estimate holds the rate flat and includes 0.5% yearly panel output decline, so rising rates would shorten payback.
Four things move payback most:
Your electricity rate. Rates range from the low teens in cents per kWh in some states to well above 30 in California and Hawaii, so high-rate states pay back faster.
Export credit rules. Lower credits for exported power lengthen payback if you export a lot.
State incentives. A credit or rebate cuts the upfront cost directly.
System price. A 10% cheaper quote shortens payback by roughly 10%.
Data visualization
25-year cumulative cash flow for a 6.0 kW system costing $20,160. Payback is about 13.5 years with no incentive, assuming electricity rates stay flat at 0% escalation. Source: SEIA Q3 2026 price, EIA 2026 rate.
Chart summary: With no incentive, the 6.0 kW system recovers its $20,160 cost in about 13.5 years and finishes year 25 about $16,237 ahead. A $5,000 state credit (the New York maximum) pulls payback to about 10.1 years. Results are simple estimates at today’s flat rate, not a quote.
Use our solar ROI calculator to project the 25-year return with your own numbers.
Method: panels = ceil(annual kWh ÷ (sun hours × 365 × 0.86) ÷ 0.4 kW); 400 W panels; payback uses a flat 18.34 cents per kWh, 0.5% yearly degradation, and no financing, battery or tax effects. This is an educational estimate, not a quote or tax advice.
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Direct answers for US homeowners — sized for a $125/month electric bill.
Most modular homes need about 11 to 25 panels of 400 W each, depending on yearly electricity use and local sun. A home that uses 8,180 kWh a year (about a $125 monthly bill) needs roughly 15 panels, or 6.0 kW, at 4.5 peak sun hours. The formula is annual kWh divided by (peak sun hours x 365 x 0.86), then divided by the panel's kW rating.
The national residential benchmark is $3.36 per watt, according to SEIA and Wood Mackenzie (Q3 2026), so a 6.0 kW system costs about $20,160 before incentives. The 30% federal homeowner credit (Section 25D) ended for systems placed in service after December 31, 2025. Some states still offer incentives; New York, for example, offers a 25% credit up to $5,000.
Usually yes. Modular homes are built in a factory to the same state and local building codes as site-built homes, so standard roof-mounted solar is generally possible. Manufactured (HUD-code) homes are a different category, so ask your installer to confirm the roof structure and check your home's warranty before any roof penetration.
It can be. For a 6.0 kW system costing $20,160 that offsets an $125 monthly bill at 18.34 cents per kWh, simple payback is about 13.5 years with no incentives, and about 10.1 years with a $5,000 state credit. Higher electricity rates shorten payback, and low export credits or heavy shading lengthen it.
Sun hours set the panel count more than home size does. A home using 8,180 kWh a year needs about 11 panels in Phoenix (roughly 6.5 peak sun hours) and about 19 in Seattle (roughly 3.5). Look up your address in NREL PVWatts before comparing quotes.
Same usage, bill-based guide
Your Modular Home 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.