Can I add a second property to my Loop account?

No, adding a smart meter from a second property is not yet possible with Loop.

However you can create a separate account to register meter(s) from another property using a different email address.

If you are a Gmail user, you can use Gmail Plus Addressing to create a variation of your email address and still receive mail to the same inbox: 

Add a “+” symbol and any word you want to the end of a gmail email address, and messages sent to it will arrive in your inbox.

For example, if your email address is colin@gmail.com, you can use colin+shopping@gmail.com, colin+loop@gmail.com, or colin+anythingyouwant@gmail.com.