What's behind these numbers

The 30% federal solar tax credit that used to apply to homeowner-purchased systems was repealed by law in July 2025, effective for any system installed after December 31, 2025. There's no partial credit and no grace period — that's why this app shows $0 for the federal credit on a cash or loan purchase, not because it forgot to add it.

A related credit technically still exists for leased/PPA systems, but it's claimed by the leasing company, not you — whether any of that value gets passed through as a lower monthly payment depends entirely on the installer, so this app doesn't guess at a pass-through and shows $0 here too.

This is general information, not tax advice — confirm current eligibility with a tax professional before making a decision.

Once your address has real coordinates (from the Mapbox lookup on the Property step), this app checks them against the Public Utility Commission of Texas's own public electric service-area boundary maps — a genuine point-in-polygon match against real utility territory, not a guess from your city name. PUCT itself labels this data "unofficial," so treat it as the best available public source, not a legal record.

Before that lookup resolves (or if it can't reach an address at all — e.g. no coordinates yet), this app falls back to a hand-checked table of roughly 40 major Texas cities, and after that, to a rough guess. The Property step always tells you plainly which of these three applies to your result, rather than presenting an estimate as settled fact.

No matter which retail electricity plan you pick, a regulated delivery company (a "TDU") still owns the poles and wires to your house, and charges a fixed fee for that — identical across every plan in your area. This app adds that charge on top of whichever plan you're comparing, using the current published rate for your utility:

The state regulator approves routine updates to these twice a year (March 1 and September 1), and a utility can occasionally get an out-of-cycle increase approved too — Oncor did in 2026. These rates will drift out of date over time; treat them as recently accurate rather than permanently fixed.

Before you upload a real quote or type in your own price, this app guesses your system's cost using a flat $2.85 per watt. That number didn't come from a "solar cost calculator" website — several of those were checked first and rejected, because they're lead-generation marketplaces whose prices are self-selected toward competitively-priced installer quotes (one even admits this directly), and one had a number that didn't match its own stated example.

Instead, this is grounded in the National Renewable Energy Laboratory's (NREL) Annual Technology Baseline, which prices real system and labor cost components directly rather than aggregating marketing quotes — their most recent published figure is $2.68/watt (2023 data). Multiple 2026 sources agree solar panel tariffs have pushed costs up roughly 10-15% since then, which lands a defensible current estimate in the $2.75-$2.90/watt range. $2.85 sits inside that range.

$2.85/watt assumes the simplest, most common case: a standard asphalt shingle or metal roof. Solar Configuration also asks what your roof is actually made of, because that changes real install labor — EnergySage's own roof-material comparison ranks tile as the most labor-intensive material to mount panels on (tiles have to be individually removed and replaced with a mounting foot and flashing) and flat/low-slope roofs as moderately more involved (ballast or tilt-angle racking instead of standard mounts). A tile roof adds an estimated $0.15/watt here, based on a real-world $500-$2,000 premium cited for an 8kW system in one sourced cost guide; a flat roof adds an estimated $0.10/watt, a softer placeholder since no dollar-specific source was found for it. Wood shake and slate roofs aren't offered as options at all — in practice those usually need the roof itself addressed before solar goes on, which a per-watt price bump can't honestly represent.

This is still just an estimate, not a quote — it's replaced entirely the moment you enter or upload a real price from an actual installer.

Most solar-specific loans include a "dealer fee" that isn't part of the system's real cost — it gets rolled into what you actually finance, usually to subsidize a lower advertised interest rate elsewhere. This isn't a rumor: the Consumer Financial Protection Bureau has published research finding these fees commonly run 10-30% of the cash price (sometimes more), and a real 2024 Minnesota Attorney General lawsuit documented a specific loan with this exact mechanic.

Because of that trade-off, this app doesn't let you set an interest rate directly — you choose the dealer fee (via the slider on Solar Configuration) and a term, and the interest rate is derived from real, cited fee/rate pairs, including the case above. Nothing here is a quote from any specific lender.

With a lease, a third party owns the system — you pay $0 upfront and a monthly fee instead, priced below what the utility would charge for that same energy (modeled here at roughly 20% below), which is why lease savings start on day one instead of after a payback period. Real lease terms cluster around 20-25 years, so that's the choice offered on Solar Configuration.

That monthly fee typically increases a little every year (an "escalator"), most commonly by around 2-3% — but some leases are sold with a flat, non-increasing payment instead, which several sources call the better deal when it's available. Rather than a slider implying more precision than real contracts actually offer, this app gives you that same two-way choice: a flat payment, or a typical ~2.5%/yr increase.

The 25-year savings chart on your Results page assumes electricity rates keep rising 3.5% a year — the same figure a real, currently operating Texas solar calculator uses in its own published projections, so it isn't an inflated sales-pitch number.

To double-check that, this app separately computed a real historical rate directly from the state regulator's own numbers: Texas's official statewide average residential rate in January 2005 versus today works out to about 3.27% a year, compounded — close to the 3.5% assumption. Both figures are shown side by side on your Results page rather than picking just one.

Texas's official plan-comparison site (Power to Choose) doesn't offer a public, documented way for an app like this to pull plans automatically and reliably. Rather than depend on something that could silently break for every visitor, the plans shown here are a manually reviewed sample — real, current plans sourced from each provider's own Electricity Facts Label — refreshed periodically by hand instead of live on every visit.

That means this isn't an exhaustive list of every plan available in your area, and coverage is currently limited to a couple of Texas utility territories, with more added over time. This app receives no payment from any provider for including, ranking, or recommending their plans — nothing shown is sponsored placement.

Texas doesn't have net metering as a matter of law. In states that mandate it, your meter effectively runs backward when you produce more than you use, so a kWh you export and a kWh you buy back later are guaranteed to be worth the same, by regulation. Texas has no such requirement — each retail electric provider (REP) sets its own export credit, and most price it well below the retail rate.

That said, "no net metering" doesn't mean no REP ever offers something close to it — a few competitive plans voluntarily price solar exports at (or near) the same rate as usage, as a product feature rather than a legal requirement. TXU Energy's "Solar Buyback System Flex" plan is a real, current example and this app's own source for that distinction: its Electricity Facts Label prices solar buyback at the plan's own indexed usage rate, so the two move together kWh-for-kWh. This app's plan data reflects that directly — see it for yourself on the Plans step for CenterPoint, Oncor, or AEP Texas Central. A plan like this is the exception, not the rule, and its rate is indexed (it moves month to month), not a fixed guarantee — but it's real, and worth specifically shopping for if a low buyback rate is your main solar concern.

That matters because most homes don't self-consume most of what their panels produce. Panels make the most power around midday; most household usage happens in the morning and evening. Earlier versions of this app netted a whole month's production against that month's usage, which hid this mismatch entirely and made "energy cost after solar" look better than a real EFL-priced plan would actually produce.

This app now estimates self-consumption from published research (the European Commission's Joint Research Centre has studied this relationship extensively, and it matches separate U.S. findings, since the underlying cause — solar timing vs. usage timing — isn't specific to any one country): a system that offsets roughly a third of a home's annual usage typically self-consumes 60-90% of what it makes, while a system sized to offset 100% of usage typically self-consumes only 20-40% of what it makes, because it's making far more than the house needs at midday regardless of size. Rather than pick one flat number, this app interpolates between real points on that curve based on your own system's offset percentage — the same technique used for the loan-rate estimate above.

Adding a home battery changes this materially: storing midday surplus for evening use instead of exporting it is directly what a battery is for, and real storage-pairing research puts a well-sized battery as lifting self-consumption by roughly 25-30 percentage points (capped at 85%, since even a good battery doesn't absorb every bit of summer midday surplus). This app uses 28 points as a representative value when you enable the battery option on Solar Configuration.

For utility territories without real plan data yet, the "energy cost after solar" fallback estimate uses this same self-consumption split, paired with a buyback-to-retail-rate ratio computed directly from this app's own real plan data (roughly 40% — the actual mean/median across every real, EFL-sourced plan shown on the Plans step that credits solar export) rather than an outside guess.

A few things in this preview are intentionally simplified stand-ins for a real API or a real site inspection that a finished product would eventually use instead:

• Sun exposure and peak sun hours on the Property step are generated from your address as a placeholder unless this deployment has an NREL API key configured, in which case they're a real figure for your exact location instead — see below.
• Solar production uses a real, weather-data-based model (NREL's PVWatts) when this deployment has an API key configured, and a simplified placeholder formula otherwise — the Solar Configuration page tells you which one is active for your estimate.
• Your monthly usage shape across the year (higher in summer, lower in spring/fall) is a hand-picked seasonal curve, not pulled from a real utility data source.