---
title: Solar Arbitrage
visibility: private
---

# ONCOR real-time arbitrage: sell to Base Power vs serve load

Status: v1 (2026-09-06, #826). Location: Pflugerville, Travis County, TX —
ONCOR wires, ERCOT South load zone (`LZ_SOUTH`). Tool:
`solar-analysis/oncor-arbitrage.sh`.

## The plan facts that shape everything

Base Power (verified 2026-09-06):
- **Import: $[redacted — LLC-private] flat** (contract through Oct 2028)
- **Export: $[redacted — LLC-private]/kWh flat** solar credit — Base does NOT pay real-time
  wholesale for exports

So on Base Power, **both sides of your meter are flat rates**. ERCOT's
real-time market price (RTM, 15-min settlement point prices) does not change
what you pay or earn today — it is a *counterfactual* and a *planning
signal*:

## Decision rules (what the tool emits)

For each kWh of solar surplus, best action = max of:
| option | value | when it wins |
|---|---|---|
| serve own/deferrable load | $[redacted — LLC-private] avoided | almost always ([redacted] > [redacted]) |
| export to Base | $[redacted — LLC-private] flat | only when NO deferrable load exists |
| export on an RTW plan* | RTM $/kWh | only when RTM > $[redacted — LLC-private] (rare spikes) |

*counterfactual — would require switching export credit to a real-time-
wholesale retailer plan (e.g. Octopus-style RTW). Texas RTW export averages
~2¢/kWh with rare spikes >$5/kWh — as a steady diet it LOSES to Base's flat
[redacted]; it only wins if you can time exports into spikes (needs battery).

**Practical rules:**
1. **Every surplus kWh has a home: load first.** HFNOC batch compute, site-2
   deferrable manufacturing, battery charging — all displace [redacted] power.
   This is why the KNELPerf class-3 batch gate keys on solar surplus.
2. **Only truly surplus-after-load gets exported at [redacted].**
3. **RTM spike alerts** (`rtw_would_beat_self_consume: true`, RTM >
   $85/MWh): under a future RTW plan you'd earn more exporting than
   self-consuming. Track how often this happens; if frequent and clustered,
   an RTW plan + battery beats Base's flat buyback for exports. Until then,
   staying on Base and self-consuming is strictly better.
4. **Battery note**: Base's free battery — verify who controls dispatch
   (Base dispatches it for grid services; if they own the dispatch, do not
   count it in household arbitrage). Open question logged on #826.

## Price sources

Official API (api.ercot.com public API) and gridstatus.io both require a
free API key; ercot.com's dashboard JSON is behind an Imperva bot-wall
(tested 2026-09-06). Tool source precedence: `RTM_OVERRIDE` →
`GRIDSTATUS_API_KEY` → `ERCOT_API_KEY` → cache file. Key registration is a
founder action ( NeedsInput on #826).

## KNELPerf integration

`oncor-arbitrage.sh` emits `start_deferrable_load` + `rtw_would_beat_self_consume`
as JSON — the batch launcher consumes this plus the HA solar-surplus sensor
once the plant is live. Docs: KNELPerf docs/ARCHITECTURE.md §7-8.

> **Docs live on Discourse — this repo is the executable source of truth.**