How dot.energy works — and where our numbers come from

The simulation

Rather than apply a flat rule-of-thumb, we run an hour-by-hour simulation of your system across a full year — the same approach professional tools like PVSyst use. We transpose sunlight onto your panels at their tilt and orientation, then subtract real-world losses: angle of incidence, heat, soiling, wiring, inverter conversion, and clipping. The result is a Performance Ratio and an annual energy figure, plus a conservative P90 (a production level you’d beat 9 years in 10) alongside the expected P50.

Weather & sunlight data

Solar resource and temperature come from NASA’s POWER dataset, a satellite-derived record of irradiance and weather. For electricity use, you can rely on a Texas-average profile, your bill, or upload your real Smart Meter Texas 15-minute interval data for the most accurate match — especially with a battery or time-of-use plan.

Your roof

We read your roof from high-resolution aerial roof analysis — the tilt and azimuth (facing direction) of each roof plane, its usable area, and how much nearby shade it gets. You can accept those values or adjust them yourself in the system editor.

How the panels are mounted also matters: flush-on-roof panels get little airflow behind them, so they run hotter and produce slightly less; a standoff air gap, an elevated rack, or a ground-mount runs progressively cooler. We set the panel cooling factor from your mounting choice, and advanced users can fine-tune it in the losses step.

Module electronics (optimizers & microinverters)

You can tell the simulator whether a panel group uses power optimizers or microinverters instead of plain string wiring. Because each panel then has its own maximum-power tracking, the model removes module-to-module mismatch and recovers much of the near-shading loss that would otherwise propagate down a series string (we recover roughly 60% of that shading loss; the light physically blocked from a shaded panel can’t be recovered). Optimizers also add a small (~0.75%) conversion loss. The payoff is largest on shaded or multi-orientation roofs; on a clean, unshaded roof the gain is smaller and comes mostly from removing mismatch.

These recovery factors are best-effort estimates, tunable as we gather field data. The specific optimizer model you pick affects equipment cost only, not production.

Electricity rates, bills & fees

For Texas, we model your bill as the utility’s delivery (TDU) charges — drawn from PUCT tariff filings — plus a representative retail-provider (REP) energy rate, with credit for solar you export at that utility’s buyback rate. Permit and interconnection fees come from each city and utility’s published materials.

Be aware: rates, buyback terms, incentives, and fees change with each tariff cycle. We label these as best-effort estimates and link to the official source on each guide so you can confirm the current figure. They’re for orientation, not a binding quote.

Independence

dot.energy is ad-supported, but nobody can pay to change your results. The energy and savings numbers come from the physics and your inputs — not from which manufacturer or installer is advertising. That independence is the whole point.