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
Building solar into a new home is usually cheaper per watt than adding it later, and it lets you design the roof around the array. But the financial picture changed in 2026. The 30% federal credit for homeowner-owned systems (Section 25D) no longer applies to expenditures made after December 31, 2025, so payback now depends mainly on your electricity rate, system price, and any state or utility incentives.
Whether you are finalizing plans with a builder or considering a house that is already finished, timing matters. Solar added during construction can be planned into the roof layout, electrical panel, and wiring. A retrofit has to work around whatever is already there. This guide compares both paths with transparent assumptions so you can check the math for your own home.
If you want a baseline before talking to a builder or installer, run your numbers through the solar savings calculator.
💰 System Cost
What Does It Cost to Build Solar Into a New Home?
A reasonable planning benchmark for installed residential solar in the US is about $3.00 per watt, though prices vary by state, installer, equipment, and roof complexity. At that price, a 7 kW system (a common size for a 2,000 to 2,400 sq ft home with moderate electricity use) costs roughly $21,000 before incentives. Treat this as an estimate, not a quote.
Data visualization
A 7 kW system costs about $21,000 at $3.00 per watt before incentives. Bars show system size in kW multiplied by 3,000 dollars per kW, with no federal credit for 2026 installs. Source: formula using the $3.00/W planning benchmark in this guide.
Chart summary. Cost scales in a straight line with system size, so every additional kW adds about $3,000 at this benchmark. A 5 kW system lands near $15,000 and an 11 kW system for a large all-electric home near $33,000. Actual quotes vary by installer, equipment, and roof, so treat the chart as a baseline for comparing bids.
A new build can cost less than an equivalent retrofit for structural reasons rather than because the hardware is different:
Combined permitting and inspections. Some of the paperwork and scheduling is shared with the rest of the build, though many jurisdictions still require a separate solar permit.
Easy roof and attic access. Installers work on an unfinished roof, with open walls and attics for wiring.
Right-sized electrical service. The builder can specify a 200-amp main panel that supports solar, an EV charger, and a heat pump from the start.
Because these savings depend on your builder and local rules, ask for a line-item solar quote rather than assuming a fixed discount.
Incentives have changed. Section 25D ended for expenditures made after December 31, 2025. Some states, utilities, and municipalities still offer rebates, tax credits, or property tax exemptions. For example, Arizona has offered a state credit capped at $1,000 and Massachusetts has offered a state credit of 15% capped at $1,000. Programs change often, so confirm current terms on the state pages or with the program administrator. If a third party owns the system through a lease or PPA, different federal rules may apply, so ask your tax professional.
💰 System Cost
What Retrofitting an Existing Home Really Costs
Retrofitting is the default path for most homeowners. The hardware price per watt is similar to new construction, but three factors can add cost: roof condition, electrical panel capacity, and wiring complexity.
Roof condition. If your roof has fewer than roughly 10 years of life left, installers commonly recommend replacing it before mounting panels. Removing and reinstalling an array later adds labor, so it is cheaper to do the roof first. Roof replacement can easily run into five figures depending on size and material.
Electrical panel. Older homes often have 100-amp or 150-amp service. Adding solar together with an EV charger or heat pump can require a service upgrade, which is commonly quoted in the low thousands of dollars. Ask your utility and installer.
Wiring and mounting. Running conduit through finished walls or along exterior surfaces takes more labor than wiring an open frame.
On the plus side, a retrofit gives you real data. Your past utility bills show actual consumption, and the finished roof shows actual shading and orientation. New-construction buyers rely on estimated loads, which can miss if a household uses more power than projected.
New Construction vs Retrofit: Side-by-Side Comparison
The table below uses the same 7 kW example system and the same assumptions for both paths. It is a model, not measured market data. Replace the inputs with your own quotes.
Factor
New construction
Retrofit
Hardware (panels, inverter)
Same
Same
Permitting and site access
Often simpler and shared with the build
Separate process, finished surfaces
Electrical panel
Specified for solar from day one
May need an upgrade on older homes
Roof
New, designed for the array
May need replacement first
Roof orientation and pitch
You choose
Fixed by the existing house
Wiring for battery or EV
Cheap while walls are open
Costlier in finished walls
Load data
Estimated
Real utility bills
Example system price (7 kW at $3.00/W)
About $21,000 before any savings from combined work
About $21,000 plus any roof, panel, or wiring extras
Panel output and degradation
Same
Same
Table summary. The panels perform identically in both cases, so the difference comes down to what surrounds the installation: soft costs, electrical upgrades, roof condition, and design freedom. A new build tends to remove the retrofit extras, while a retrofit tends to provide better load data. Your electricity rate sets payback in both cases.
Payback is easy to estimate. At 1,300 kWh per kW per year, a 7 kW system produces about 9,100 kWh. At 17¢/kWh (a rough national-average assumption), that is about $1,550 a year in avoided electricity, which gives a simple payback near 13.6 years on $21,000. At 30¢/kWh, the same system saves about $2,730 a year and pays back in under 8 years. Your rate matters more than your build method. Panel output declines about 0.5% a year in NREL’s long-term field analysis, so a system keeps roughly 94% of its output after 12 years.
Data visualization
Payback drops from 19.2 years at 12 cents per kWh to 5.8 years at 40 cents. Simple payback equals 21,000 dollars divided by 9,100 kWh times the rate, with no rate escalation and no incentives. Source: formula using the 1,300 kWh per kW assumption; check your rate in the EIA state electricity table.
Chart summary. Electricity rate moves payback far more than build method does. The same 7 kW system takes about 19 years to pay back at 12¢/kWh and under 6 years at 40¢/kWh. Find your utility rate in the EIA state electricity table before relying on any payback estimate.
📋 Key Insights
Design Advantages You Only Get at Construction Time
Roof orientation and pitch. In the Northern Hemisphere, a south-facing roof plane generally yields more annual energy than east or west planes, and the best tilt depends on latitude. During design you can set the ridge direction and pitch. Use NREL’s PVWatts to compare options for your address.
Clean array layout. You can keep vents, plumbing stacks, chimneys, and skylights off the best roof area, and avoid shading from dormers.
Battery and EV readiness. Conduit, space on the wall, and a properly sized panel are cheap to include while framing is open. Even if you do not buy a battery now, pre-wiring preserves the option. Batteries matter more where utilities pay little for exported power, such as under California’s NEM 3.0 rules.
Roof-integrated products. Solar roofing products replace part of the roofing material and are generally only practical at construction or reroofing. They usually cost more per watt than standard rack-mounted panels, so compare total roof-plus-solar cost rather than solar price alone.
Solar mandates and programs. California has required solar on most new low-rise residential buildings since January 1, 2020 under its building code. Other jurisdictions encourage “solar-ready” construction with reserved roof space and conduit. Check what applies where you are building.
💰 System Cost
Sizing, Financing, and Incentives After 2025
Sizing. Start with 12 months of utility bills for an existing home. For a new home, use the builder’s load calculation and add expected EV and heat-pump use. Production per installed kW varies from roughly 1,100 to 1,600 kWh per year across the US, so use PVWatts for your address instead of a single national divisor. Oversizing may not pay off where your utility credits exports at a low rate.
Financing. Cash purchases avoid interest. Solar loans let you spread the cost, and rolling solar into a construction mortgage can lower the interest rate compared with an unsecured loan. As a rough comparison, $21,000 financed over 20 years at 7% is about $163 a month. In the 17¢/kWh example above, bill savings are about $129 a month, so the loan costs more than it saves. At higher electricity rates, the monthly math improves. Run your own numbers in the solar ROI calculator.
Data visualization
A 7 kW system nets about $15,400 over 25 years at 17 cents per kWh and about $43,200 at 30 cents. Cumulative cash flow starts at minus 21,000 dollars, assumes 9,100 kWh in year one, 0.5 percent annual degradation, flat rates, and no incentives. Source: formula using NREL degradation findings.
Chart summary. Each line crosses zero at the break-even year: roughly year 14 at 17¢/kWh and year 8 at 30¢/kWh. After break-even, the gap grows every year, but the lines assume flat electricity rates. If your utility raises rates, the real curve will be steeper, and if rates fall or export credits shrink, it will be flatter.
Home value. A Lawrence Berkeley National Laboratory study (2015) estimated a premium of about $4 per watt for owned solar, and a 2019 Zillow analysis found about a 4% sale premium. Premiums vary by market, and leased systems generally do not carry the same benefit.
Incentives. Section 25D no longer applies to expenditures made after December 31, 2025. Look at your state, utility, and city programs, net metering rules, and whether a lease or PPA is better in your situation. Because rules shift often, confirm current terms before you sign. See the state pages and the net metering calculator.
This guide is general information, not tax or legal advice.
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Usually yes, per watt. A build-in system shares permitting, site access, and electrical design with the rest of the house, and the builder can size the main panel for solar, EV charging, and a heat pump from day one. A retrofit can add costs such as a panel upgrade, wall or attic wiring, or a roof replacement. The size of the gap varies by market and builder, so compare itemized quotes for both. The panels themselves produce the same power either way.
Research suggests it can. A Lawrence Berkeley National Laboratory study (2015) found owned solar systems sold at a premium of about $4 per watt, and a 2019 Zillow analysis found homes with solar sold for about 4% more than comparable homes. Results vary by market, and leased systems generally do not add the same value because a buyer must take over the lease. Treat these figures as market averages, not guarantees.
For a system you own, generally no for 2026. The Residential Clean Energy Credit (Section 25D) does not apply to expenditures made after December 31, 2025. Systems owned by a third party (lease or PPA) may qualify for a different business credit under separate rules and deadlines, and some states and utilities still offer incentives. Confirm current rules with the IRS and a tax professional before signing.
Often yes. Running conduit and leaving space and structural support for an inverter, battery, and EV charger is done while walls are open, so it is typically much cheaper than opening finished walls later. Ask your builder for a line-item price. Many building codes and programs also define 'solar-ready' requirements, such as reserved roof area and conduit, so check what your jurisdiction requires.
Start with the builder's load estimate, then add expected EV and heat-pump use. An EV driven about 12,000 miles a year uses roughly 3,000 to 4,000 kWh. Production per installed kW commonly ranges from about 1,100 to 1,600 kWh a year depending on location, so divide annual kWh by your local figure. Use NREL's PVWatts calculator for your exact address and roof direction, and avoid oversizing if your utility pays little for exported power.
$150/month electric bill by state
System size and payback vary by electricity rate and sun hours — see your state.
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.