Support

• Web: a current version of Chrome, Edge, Safari or Firefox, on a PC, Mac, Chromebook, tablet or phone, with JavaScript on and site data (local storage) allowed. Full Access needs a connection to check your license key and load the question bank. There is nothing to install.
• App: an iPhone or iPad running iOS 26.0 or later, or a Mac running macOS 26.0 or later. The app works offline; it contacts the App Store only for the optional Full Access purchase, and iCloud only to sync your progress. It appears as "Grid Prep" under its icon.

The web app is free to start: 50 practice answers and one 30-question mock taster, timed at exam pace. Full Access is US$24.99 once, with no subscription. Lemon Squeezy runs the checkout and emails you a license key.

• Unlock: open the web app, choose Unlock, and paste the key. It works in up to five browsers.
• Moving to a new computer: in the old browser, open Settings and use "Free this device's slot". Your progress stays with your license key and comes back wherever you enter it again.
• Lost the key? It is in the Lemon Squeezy email. If you can't find it, email us with the address you bought with.

A web license doesn't unlock the app, and the app's in-app purchase doesn't unlock the web.

The app is free to try: 50 practice questions in any mode, one full mock paper on any credential, one simulator run and the whole Library. Full Access is a single one-time in-app purchase that unlocks every question, unlimited mock papers on all four credentials and every trainer, on your iPhone, iPad and Mac. It follows your Apple Account: on another device it unlocks by itself, or tap Restore purchases in Library › About. Downloaded the app before version 1.2? You keep everything, free.

Tap or click an option to choose it, and change your mind if you like. Then Confirm answer to see whether it was right, with the explanation and its reference. On a keyboard, A–D or 1–4 choose an option and Return confirms it, then moves to the next question. In a mock exam there is no feedback until you submit; flag a question to come back to it.

• Web, free: progress stays in the browser you study in. Clearing that browser's site data clears it.
• Web, Full Access: your answers, review schedule and mock papers follow your license key to every browser where you unlock it. Each browser keeps its own copy, so a dropped connection catches up later. Appearance and the chosen credential stay on each browser.
• App: from version 1.4 your iPhone, iPad and Mac combine their progress through your own iCloud account. The switch is in Library › Sync, and it is on unless you turn it off.
• Starting over: "Reset all progress" is in Settings on the web and at the bottom of the Library tab in the app. With sync on it clears every synced browser or device; the free-tier counters and your Full Access unlock stay.

All four examinations are drawn from the same six content domains and the same 31 knowledge areas. What differs is how many scored questions each area contributes, and NERC publishes that table for every credential. So Grid Prep carries one question bank and one progress record: picking a credential re-weights your readiness estimate, the order of your weak areas, and the way a mock exam is sampled. An answer counts toward all four.

NERC passes candidates on a cut score, a count of correct answers: 92 of 120 for RC and BT, 76 of 100 for TO and BI. So Grid Prep shows a projected score out of the paper, and ranks knowledge areas by how many scored questions they are costing you on the credential you picked.

Every question carries an explanation and a reference. If you believe an answer conflicts with the currently enforceable standard, email the question text and your reference. Verified corrections ship in the next update. Reliability Standards are revised regularly: always treat the current enforceable standard at nerc.com, and your own entity's operating procedures, as authoritative.