When using the Google Maps API you are using a service provided by Google. Google does provide this service free for a certain amount of "calls" in a single day. To see what your limit is you can easily check within your Google Developers Console here:

https://console.developers.google.com

Once there you would:

and within the next page you would click the "Google Maps Embed API" link shown here:

Within that next page you will see the specifics on that API if you click "Quotas" as seen here:

If you like you can see the stats on using that API key over the last few days, weeks and months by clicking the "Usage" link:

<tip c w>An important thing to note is that once you use up your quota in a day your clients will see a message in any page that displays the google map that says something to the effect that you have "exceeded your limit" for that API key. So if you do not want this to happen you should arrange to leave a credit card for Google to bill for overages. You would still get your free quota in a day but would be billed for any overages above that limit and your clients would never see the "API exceeded limit" message unless of course you credit card couldn't be charged.</tip>