Set up your own Google Gemini key, with billing and a spend cap

Google still offers a free Gemini allowance, but it is now very small. Google cut it sharply in December 2025 and no longer publishes the figures; developers report around 20 requests a day for the Flash models. A single survey can use that up before lunch, and then the AI tools stop with a “quota” or “rate limit” message. That is why we recommend turning billing on.

• You pay Google, not us. Your DampApp Pro subscription does not include Google's charges. Google bills you directly for what you use.
• Google's US$300 free trial does not cover Gemini. Google says trial credit cannot be used for the Gemini API.
• Most new accounts prepay. You buy credit first (at least US$5), and when it runs out the AI simply stops. That makes the balance a built-in spending limit. Credit expires after a year.
• Billing also keeps your clients' data out of Google's training. On the free tier, Google may use what you send to improve its products and people may review it, unless you are in the UK, EEA or Switzerland, where Google applies its paid-tier protections to everyone. With billing on, Google says it does not use your prompts or photos to improve its products, wherever you are.

1. 1

   Step 1: Open Google AI Studio and sign in

   Sign in with your Google account. The first time, Google asks you to accept its terms, then creates a project and a key for you automatically.

   Open Google AI Studio (opens in a new tab)

   A “project” is just Google's name for the folder your key and bill live in. You do not need to change anything in it.

2. 2

   Step 2: Create your key

   On the API keys page, click “Create API key”. If Google asks which project to use, pick the one it made for you. Your new key appears in the list.

   • If Google already made a key for you in step 1, you can use that one.
   • Keys made since 28 May 2026 are automatically limited to the Gemini API, which is what you want.
   • You will copy the key in step 6, so leave this page open.
3. 3

   Step 3: Turn on billing

   Open the Projects page and click “Set up billing” in the “Billing Tier” column next to your project. (Google also shows a “Set up billing” link on other pages; any of them works.)

   Open the Projects page (opens in a new tab)

   1. Choose your country and accept the terms.
   2. Add your payment card.
   3. If Google asks you to prepay, buy the smallest amount it offers (at least US$5). If it offers a choice between “Prepay” and “Postpay”, choose Prepay: the AI then stops when your credit runs out, so you can never owe more than you paid.

   UK customers pay 20% VAT on top. Google says the higher usage limits usually switch on within a few minutes.

4. 4

   Step 4: Leave auto-reload off

   On the Billing page, Google offers “Auto-Reload”, which buys more credit whenever you run low. It is optional. Leave it off if you want your balance to be the most you can spend, and top up by hand when you need to.

   Open the Billing page (opens in a new tab)

   If you do turn it on, set its “Monthly Auto-Charge Limit” so it can only top up so much each month.

5. 5

   Step 5: Set a monthly spend cap

   This is your safety net, and essential if you chose Postpay. Open the Spend page, find “Monthly spend cap”, click “Edit spend cap”, type an amount such as 10 (US dollars) and save.

   Open the Spend page (opens in a new tab)

   Google labels the cap “experimental” and says it can take about ten minutes to kick in, so spending can go slightly over. Google also caps new billing accounts itself, at US$250 a month on its first usage tier.

6. 6

   Step 6: Paste the key into DampApp Pro

   On your phone or tablet, open DampApp Pro and go to SettingsIntegrations. Settings is the gear at the bottom right of the home screen.

   1. Under “AI Provider”, tap “Google Gemini”.
   2. Tap the “Google Gemini API Key” box and paste your key. It is a long string of letters, numbers and symbols. Google changed its key format in 2026, so yours may not look like the grey example in the box. Tap the eye icon to check it pasted in full, with no space at the end.
   3. Scroll down and tap “Save & Sync Settings”.

   

   

   

   The Integrations tab shows these boxes to Pro subscribers. If you are signed in, saving also keeps the key in your secure cloud profile, so it follows you to your other devices.

7. 7

   Step 7: Check it works

   Open any survey, type a rough note into a text box that has an “AI Polish” button (for example “damp patch by back door, plaster blown”), then tap “AI Polish”. It has a sparkle icon. If the note comes back rewritten, you are done. You will not see the app's daily AI limit again while your key is saved.

   If you see a message instead, look it up in If something goes wrong below.

Google charges by the amount of text and pictures the AI reads and writes. The app asks for Google's latest “Flash” model, which is its fast, lower-cost range. Our estimates, before VAT:

Estimated from Google's published Flash prices (for example Gemini 3.5 Flash at US$1.50 per million word-pieces read and US$9 per million written). Google's newest models also “think” before answering and charge for that, so costs vary. Your real spend is on the Usage (opens in a new tab) and Spend (opens in a new tab) pages.

Your key lets anyone who has it use your Google credit, so treat it like a card number.

• Never post it online, email it to someone else, or share a screenshot that shows it.
• DampApp Pro support will never ask for your key.
• Google blocks keys it finds published online. You would then see a message that your key was “reported as leaked”: delete it and create a new one.
• If your key says “Unrestricted” in AI Studio, hover over that label, choose “Add restrictions”, then “Restrict to Gemini API only” and “Restrict key”. Google now blocks unrestricted keys that sit unused for a long time.