How we calculate what we show

The rule that governs everything

Facts do not live in prose. They live in structured records that carry a value, a named source, the method by which the value was verified, and the date it was checked. Pages read those records through a single function that refuses to return a value when it is unverified, outside its effective window, or older than its freshness policy allows.

The consequence is that a missing number changes the shape of the page rather than leaving a placeholder in it. There is no path in this codebase by which an unsourced figure can appear as text.

Solar production

Production comes from NREL PVWatts, run per location under a fixed set of assumptions so that figures are comparable between cities:

• Model: NREL PVWatts v8
• Array type: Fixed roof mount
• Module type: Standard
• Tilt: 20°
• Azimuth: 180° (due south)
• System losses: 14%

These figures have not been ingested yet. Until they are, every page whose answer depends on modelled production is held back, and the estimator says so rather than substituting a plausible yield. A real roof rarely faces due south at exactly this tilt, so even once ingested these are a comparable baseline rather than a prediction for your home.

System sizing

Sizing starts from your annual consumption, not your roof or your budget. Florida PSC Rule 25-6.065 requires a net-metered system not to be expected to produce more than 115% of annual consumption, so that ceiling is applied first. Converting the resulting kilowatt-hour figure into kilowatts requires the specific yield above.

The ceiling is a regulatory fact rather than a model output, which is why our estimator can state it today while declining to state a system size.

Battery sizing

Battery recommendations are derived from published usable capacity and continuous output in manufacturer datasheets, matched against a backup objective. Output is treated as the binding constraint, because it determines what can be switched on at all, while capacity determines only how long.

Our backup duration calculator applies a duty cycle to loads that cycle rather than run continuously. It does not model motor starting surges, which are handled by a battery’s peak rating and are where undersized systems typically fail. It is a planning tool, not a load calculation.

Pricing

We publish no installed prices. Helio41 has no installation partner price sheet for Florida, no completed installations, and therefore no dated basis for a price. When a partner price sheet exists, prices will appear with the date and basis attached, and the pages currently held back for pricing will publish without a word of their prose being rewritten.

We also publish no market statistics of our own. When we have enough real quotes to say something like “based on 184 Helio41 estimates in Palm Beach County over 90 days”, the sample size will be a real count from a real dataset.

Freshness

Each source category carries a maximum age. Electricity rates and incentives expire hard, because a stale figure there is actively misleading — those values are withheld from pages once past their window rather than shown with a caveat. Tariff rules, specifications and warranties are given longer windows and raise a warning rather than disappearing. Coordinates and methodology change rarely.

What this model cannot do

• It cannot see your roof, its orientation, its pitch, or what shades it.
• It cannot assess your electrical panel, which is a common source of unexpected cost.
• It cannot perform the load calculation that decides what a battery will actually run.
• It cannot quote you a price, and does not pretend to.

Estimator methodology version 0.1. If you find something wrong here, tell us — a correction to a source record corrects every page that depends on it.