Should service layer return entity model that isn't mapped to an actual database table?

I have a web app with following design.

View -> Controller -> Service || Repository -> DB

For example :

Entity Model

public class Customer
{
    [Key]
    public int CustomerID { get; set; }
    public char Gender { get; set; }
    //rest of property here..
}

Context

public class TestContext : DbContext
{
    public DbSet<Customer> Customers { get; set; } //register entity class as DbSet
    ...

Repository

public IEnumerable<Customer> List()
{
    return _customer.AsEnumerable();
}

public void Insert()
{
    //...
}

public void Update()
{
    //...
}

Service

public IEnumerable<Customer> MaleCustomerList()
{
    return _repo.Customer.List().Where(w => w.Gender == "M");
}

public IEnumerable<Customer> FemaleCustomerList()
{
    return _repo.Customer.List().Where(w => w.Gender == "F");
}

So far we have no problem because service is returning entity model which is mapped to an actual database table. But what if I need to do some complex queries that return a completely different object, for example I need to group certain customer and calculate their percentage. I will need to return something like IEnumerable<CustomerGroup> where CustomerGroup is completely different with Customer, but it is not an actual table (because I don't need it) in the database.

So my question is, is it okay to make a new Entity model

public class CustomerGroup
{
    public int GroupName { get; set; }
    public decimal Percentage { get; set; }
}

but the different is that it's not registered in the Database Context DbSet so my service can return this type?