Solar Panels for 20 kWh/Day
Est. net savings
$1,241
At ~17¢/kWh, 100% offset · no federal credit
Typical result:
- 13–18 panels (400 W each)
- 5.6 kW system at 4.5 sun hours
- ≈$14,400–$19,600 before incentives
- ≈11.6-year simple payback (low-cost quote, ~17¢/kWh)
How Big a Solar System Do You Need for 20 kWh/Day?
To offset 20 kWh of daily use, your system has to produce about that much on an average day after real-world losses (inverter efficiency, wiring, heat, dust, and shading). The standard planning formula is:
System size (kW) = Daily kWh ÷ Peak Sun Hours ÷ 0.80
The 0.80 factor is a conservative planning allowance for system losses. NREL’s PVWatts calculator defaults to about 14% losses, which equals roughly 0.86, so your installer’s modeled number may come out slightly smaller. Peak sun hours range from roughly 3.5 in cloudier parts of the country to about 6 in the Desert Southwest, so location changes the answer a lot. At the common 4.5-hour benchmark: 20 ÷ 4.5 ÷ 0.80 = 5.6 kW.
System Size and Panel Count for 20 kWh/Day by Peak Sun Hours (calculated)
| Peak Sun Hours | Required System Size | 400 W Panels Needed |
|---|---|---|
| 3.5 | 7.1 kW | 18 |
| 4.0 | 6.3 kW | 16 |
| 4.5 | 5.6 kW | 14 |
| 5.0 | 5.0 kW | 13 |
| 5.5 | 4.5 kW | 12 |
| 6.0 | 4.2 kW | 11 |
Panel counts are rounded up to the next whole panel. If you choose higher-wattage panels (many 2026 models are 420–450 W), you need fewer of them for the same system size. Use our solar system size calculator to enter your ZIP code and get a location-specific panel count.
Chart summary: The same 20 kWh/day load needs about 7.1 kW of panels (18 × 400 W) at 3.5 sun hours and about 4.2 kW (11 × 400 W) at 6.0 sun hours, a spread of roughly 70%. Your local sun hours are the single biggest input to your panel count, so check your address in PVWatts before ordering.
What Does a Solar System for a 20 kWh/Day Home Cost in 2026?
Installed price is usually quoted in dollars per watt, so the formula is simple: system size in watts × price per watt. Two widely cited benchmarks bracket what U.S. homeowners pay. EnergySage reported an average of about $2.58 per watt before incentives in early 2026, based on competing quotes in its marketplace. Lawrence Berkeley National Laboratory’s Tracking the Sun report put the 2024 national median for cash-purchased systems closer to $3.50 per watt. The gap is largely the difference between shopping multiple quotes on a marketplace and accepting a single door-to-door offer.
Estimated Cost Before Incentives (calculated from per-watt benchmarks)
| System Size | 400 W Panels | At $2.58/W (EnergySage avg.) | At $3.50/W (LBNL 2024 cash median) |
|---|---|---|---|
| 5.0 kW | 13 | $12,900 | $17,500 |
| 5.6 kW | 14 | $14,448 | $19,600 |
| 6.4 kW | 16 | $16,512 | $22,400 |
| 7.0 kW | 18 | $18,060 | $24,500 |
Larger systems usually cost less per watt because fixed costs such as permitting, design, and crew time are spread across more panels, so treat these figures as estimates, not quotes.
Chart summary: For the 5.6 kW system most 20 kWh/day homes need, the difference between a competitive marketplace quote and the national cash-purchase median is about $5,150 ($14,448 vs. $19,600). Price shopping can matter as much as system size.
What happened to the 30% federal tax credit? Under the One Big Beautiful Bill Act signed July 4, 2025, the Section 25D residential clean energy credit ended for expenditures made after December 31, 2025. Systems that homeowners buy and complete in 2026 generally do not qualify, and the IRS has said the credit year is tied to when the system is installed, not when you signed or paid. Unused 25D credit from an earlier year can still be carried forward, and companies that own leased or PPA systems may claim a business credit under Section 48E, subject to its own rules. See the IRS residential clean energy credit page and ask a tax professional about your situation.
What incentives can still help? Some states, utilities, and local governments offer rebates, property-tax exemptions, sales-tax exemptions, or favorable net-metering terms. DSIRE, the Database of State Incentives for Renewables & Efficiency, tracks them by state and is the best place to check what applies to you. Our solar tax credit calculator can help you account for whatever applies once you know it.
Real-World Output: How Much Will a 5.6 kW System Produce?
A quick way to sanity-check your system size is to estimate annual output. For a 5.6 kW system in a location with 4.5 peak sun hours and the 0.80 planning factor:
5.6 kW × 4.5 hours × 0.80 × 365 days ≈ 7,358 kWh per year (≈20.2 kWh/day)
Modeling Assumptions for the 5.6 kW Example
| Input | Value |
|---|---|
| System size | 5.6 kW (14 × 400 W panels) |
| Peak sun hours | 4.5 per day (annual average) |
| Planning factor (losses) | 0.80 |
| Estimated annual output | ≈7,358 kWh |
| Average daily output | ≈20.2 kWh |
| Target daily use | 20 kWh |
This is an annual average. Output is higher in summer and lower in winter, with larger seasonal swings the farther you are from the equator and the cloudier your climate. If your utility offers net metering, summer surplus can earn bill credits that offset winter shortfalls. If it does not, or credits are paid at a lower export rate, a system sized to your annual total may leave you buying more grid power than the annual math suggests. California’s NEM 3.0 rules, for example, pay export credits based on avoided-cost rates rather than the full retail rate.
Three things change real output the most:
- Roof direction and tilt. In the continental U.S., south-facing arrays generally produce the most per year. East- or west-facing roofs typically produce somewhat less, which is often offset by adding a panel or two.
- Shading. Trees, chimneys, and neighboring buildings can cut output sharply, especially with a basic string inverter. Microinverters or optimizers can limit the loss.
- Panel and inverter quality. Higher-efficiency panels fit more watts on a small roof, and panel degradation is typically a fraction of a percent per year.
To model your actual roof, enter your address in NREL’s PVWatts calculator or use our solar output calculator before you finalize system size.
Solar Payback Period for a 20 kWh/Day Home (Without the 30% Credit)
Simple payback is net system cost divided by annual savings. The table shows how payback changes with your electricity rate, and the chart below shows the year-by-year cash flow at 17¢/kWh. With the federal homeowner credit gone for 2026 completions, net cost for a customer-owned system equals gross cost unless you have state or local incentives. A system that offsets 20 kWh/day avoids about 7,300 kWh of purchases per year, so annual savings equal 7,300 times your retail rate (assuming full-retail net metering or self-consumption, and no rate increases, degradation, or maintenance costs).
Simple Payback for a 5.6 kW System by Electricity Rate (calculated)
| Retail Rate | Annual Savings | Payback at $2.58/W ($14,448) | Payback at $3.50/W ($19,600) |
|---|---|---|---|
| 12¢/kWh | $876 | 16.5 years | 22.4 years |
| 17¢/kWh | $1,241 | 11.6 years | 15.8 years |
| 20¢/kWh | $1,460 | 9.9 years | 13.4 years |
| 25¢/kWh | $1,825 | 7.9 years | 10.7 years |
| 30¢/kWh | $2,190 | 6.6 years | 8.9 years |
Chart summary: With no incentives and a constant 17¢/kWh rate, the low-cost system ($14,448) turns cash-positive in year 12 and reaches about $16,600 of cumulative savings by year 25. The higher-priced system ($19,600) breaks even in year 16 and reaches about $11,400. The gap between the lines is the price difference between quotes, which is why comparing installers matters. Rising utility rates would shorten both curves; reduced export credits would lengthen them.
Utility rates have risen in recent years, and if they keep rising your real payback will be shorter than these constant-rate figures; if your utility cuts export credits, it will be longer. States with some of the highest residential rates, such as Hawaii, California, and the Northeast, tend to see the shortest paybacks. Check your current rate on your utility bill or in the EIA Electric Power Monthly, then run your numbers in our solar payback calculator.
Is Solar Worth It for a 20 kWh/Day Home — Cash, Loan, or Lease?
For many homeowners with moderate-to-high electricity rates, solar can still make financial sense even without the 30% federal credit, but the margin is thinner than it was in 2025, and the financing method decides who captures the savings.
Financing Options Compared for a Customer-Owned vs. Third-Party-Owned System
| Option | Upfront Cost | Who Owns the System | Main Trade-Off |
|---|---|---|---|
| Cash purchase | Full system price | You | No financing cost, highest long-run savings, but the largest upfront outlay |
| Solar loan | Often $0 down | You | Interest and dealer fees raise total cost, so compare the APR and the cash price |
| Lease | Often $0 down | Third party | Fixed monthly payment, sometimes with annual escalators, and the owner keeps any tax credit |
| Power purchase agreement (PPA) | Often $0 down | Third party | You pay per kWh produced, and contract terms matter when you sell your home |
Because the 25D credit has ended, the usual comparison has shifted: third-party owners may still be able to claim a federal business credit and, in some cases, pass part of that value through as lower payments, while a loan or cash purchase generally does not receive it. That does not automatically make a lease better, since you usually get a smaller share of the savings and take on contract terms to review (escalators, transfer at sale, and buyout options).
Three factors usually decide whether solar is worth it for you: your electricity rate, your net-metering or export-credit terms, and how long you will stay in the home. Home-value effects vary by market, so do not count on a resale premium without local evidence. Get at least three written quotes, ask for the price per watt, the equipment model numbers, and the production estimate, and compare them against PVWatts. Use our solar savings calculator to estimate your break-even year with your own utility rate and system price.
Sources and methodology: Per-watt prices are from EnergySage’s 2026 marketplace data and the Lawrence Berkeley National Laboratory Tracking the Sun report. Tax-credit status reflects the One Big Beautiful Bill Act and IRS guidance. Output modeling uses the standard sizing formula and can be checked with NREL PVWatts. Incentive programs are tracked by DSIRE. All charts and tables labeled “calculated” are derived from the stated formulas and inputs, not measured data from a specific installation. This guide is educational and not tax, legal, or financial advice. Last reviewed October 3, 2026.
Frequently asked questions
Direct answers for US homeowners — sized for a $100/month electric bill.
Same usage, bill-based guide
Your 20 kWh/Day target maps to roughly a $100/month electric bill nationally.
$100 $100/month electric bill guidePopular state solar guides
Electricity rates and incentives vary — see data for your state.
How these numbers were calculated
- Electricity rate
- 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).
- Model
- Version 2026.10 · 3%/yr electricity price escalation · 0.5%/yr panel degradation · simple payback = installed cost ÷ year-1 savings
- Policy checked
- · Full methodology · Report an error
Estimates only — not tax, legal or financial advice. Get at least three installer quotes and confirm incentives with your utility and a tax professional.