How We Calculate Your True Texas Electricity Bill
TexasPowerCost.com estimates your real monthly electricity bill by interpolating each plan's official Electricity Facts Label (EFL) rates to your actual usage, cycling your seasonal usage across the full contract term, and accounting for regulated TDU delivery charges — instead of relying on the single, often-misleading 1,000 kWh advertised rate.
Last updated:
By the TexasPowerCost Editorial Team — independent Texas electricity analysis · Last reviewed October 18, 2026 · how we analyze plans
What makes this comparison different
The most accurate way to compare Texas electricity plans is by what you would actually pay at your own usage — not the advertised rate at 1,000 kWh. Most comparison sites rank on that single 1,000 kWh marketing benchmark, which every provider engineers their plan to win. TexasPowerCost ranks by your true monthly cost instead: we compute each plan's effective rate at your actual usage from all three official EFL price points (500, 1,000 and 2,000 kWh) — not just the 1,000 kWh figure — then add the regulated TDU delivery charge. Because that math is usage-specific, the plan that is genuinely cheapest changes with how much you use — something the advertised 1,000 kWh rate can never show. We call this usage-based, EFL-interpolated approach Real-Rate Interpolation.
Real-Rate Interpolation vs. advertised-rate tools
Most Texas comparison tools rank plans on a single marketing number — the advertised average at exactly 1,000 kWh. Real-Rate Interpolation ranks on what you would actually pay. Here is the practical difference:
| How it ranks plans | Typical advertised-rate tool | Real-Rate Interpolation (this site) |
|---|---|---|
| Rate used to rank | Advertised average at exactly 1,000 kWh | Effective rate computed at your usage |
| Uses all three EFL price points | No — usually just the 1,000 kWh figure | Yes — interpolates across 500 / 1,000 / 2,000 kWh |
| Reflects seasonal swings | No — one flat number all year | Yes — cycles your 12-month profile across the term |
| Exposes bill-credit "V" pricing | Hidden | Surfaced — the cheapest plan changes with usage |
| Regulated TDU delivery charge | Often omitted from the headline rate | Treated as a per-ZIP pass-through on top of energy |
The net effect: the plan that ranks #1 under Real-Rate Interpolation is frequently not the one that ranks #1 on advertised rate — which is the whole point of the 1,000 kWh illusion.
Want to apply this yourself, by hand or on any other tool? See how to compare Texas electricity plans by usage for the step-by-step method, and what makes a good Texas electricity comparison site for the seven criteria to judge any comparison tool against — including this one, with our own disclosure.
The 1,000 kWh illusion
Every Texas electricity plan publishes an "average price" at 500, 1,000 and 2,000 kWh on its EFL. Comparison sites almost always rank plans by the 1,000 kWh number — so providers engineer that single data point to look as cheap as possible, frequently using a bill credit that only applies at or near 1,000 kWh. A household that uses 1,250 or 1,800 kWh in a hot Texas summer can end up paying a dramatically higher effective rate than the headline figure suggests. Ranking plans on the advertised 1,000 kWh rate is the single most common way Texans overpay. Our 1,000 kWh Illusion guide works through a side-by-side example showing how a bill-credit plan flips from cheapest to most expensive as usage moves away from 1,000 kWh.
We measured this across the Texas market. Looking only at standard fixed-rate plans (excluding variable and free-nights plans for a like-for-like comparison), a large home using ~2,000 kWh that picks the plan advertised cheapest at 1,000 kWh pays about $57 more per month — roughly $686 a year than the fixed plan that is actually cheapest at that usage.
Want this run for your own home? Run a free 10-second bill checkup → — enter your ZIP and real usage and we apply exactly this method to show your real ¢/kWh, the cheapest plan at your usage, and a plain-English switch / wait / verify verdict.
Linear interpolation across the EFL price points
Because the EFL only publishes three points, we calculate the straight-line slope between them to find the precise per-kWh rate at your real usage. If your usage sits between 500 and 1,000 kWh, we interpolate along that segment; between 1,000 and 2,000 kWh, we use that segment instead. The result is the effective rate at your consumption level, not a marketing benchmark. This per-usage precision is the core of our engine and the main thing that distinguishes our estimates from a simple rate table.
Full-term seasonal usage cycling
Texas weather drives extreme seasonal swings. A plan that looks affordable in spring can become expensive during a 100°F summer peak. Our engine applies your 12-month usage profile across the entire contract — whether 12, 24 or 36 months — so the projected average monthly cost reflects every heatwave and cold snap you will actually encounter before the contract expires, rather than a flat 1,000 kWh assumption for every month.
Why we rank on average monthly cost, not total contract cost
When plans have different term lengths, total contract cost is misleading: a 36-month plan will always total more than a 12-month plan even when its rate is lower. We therefore prioritise the average monthly cost and the effective rate (¢/kWh) — a level playing field that lets you compare a short and a long plan fairly on what you will actually pay each month.
TDU delivery charges are separate
Your bill has two parts: the energy supply rate set by your retail provider, and the delivery charges set by your Transmission & Distribution Utility (TDU). Each Texas ZIP belongs to exactly one TDU — Oncor (Dallas/Fort Worth), CenterPoint Energy (Houston), AEP Texas (West/Central Texas) or TNMP (smaller areas) — whose regulated, pass-through charges are approved by the Public Utility Commission of Texas (PUCT). These apply no matter which provider you choose, and the official EFL is always the final authority on a plan's total charges.
Where our data comes from
Plan rates are sourced from the official Texas Power to Choose dataset and synced regularly. The "last updated" date shown on each city, ZIP and plan page reflects the most recent successful sync for that area, so you always know how current the figures are. Our estimates are a transparent mathematical projection for comparison; before enrolling, always read the plan's official Electricity Facts Label for the governing rates and terms.
Frequently asked questions
Why is the advertised 1,000 kWh rate misleading?
Providers optimise the headline 1,000 kWh rate for marketing because it is the number shown on comparison sites. Bill credits and tiered pricing are often engineered to look cheapest at exactly 1,000 kWh. If your usage differs, your real rate can be very different, which is why we interpolate to your actual usage.
What is linear interpolation and why use it?
Linear interpolation estimates the rate between two known EFL price points by following the straight-line slope between them. Because Texas plans only publish rates at 500, 1,000 and 2,000 kWh, interpolation gives an accurate per-kWh rate at any usage level in between — for example 1,250 or 1,750 kWh.
Do your estimates include TDU delivery charges?
Energy supply rates and TDU (utility) delivery charges are separate. Each Texas ZIP belongs to exactly one TDU — Oncor, CenterPoint, AEP Texas or TNMP — whose regulated pass-through charges are set by the PUCT and added on top of the energy rate. Always confirm the full charges on the official EFL.
How fresh is the rate data?
Plan data is synced regularly from the official Texas Power to Choose dataset. The "last updated" date shown on each rate page reflects the most recent successful sync for that ZIP.
Want this run on your own bill?
The free Bill Analyzer applies this exact method to every plan in your ZIP at your real usage and gives you a plain-English verdict — switch, wait, or verify first.
Run a free bill checkup →Estimates are a mathematical projection based on public Power to Choose / PUCT data and are provided for comparison purposes only. Actual bills depend on metered usage and the full terms in each provider's Electricity Facts Label (EFL) and Terms of Service.