"We last raised an equity round in the summer of 2015 and haven't had a need to raise capital since. This is because we are very capital efficient and have been since our founding."

If you haven't had a need to raise capital since your founding because your were capital-efficient, then why did you raise an equity round in 2015?

Either your statement is worded inaccurately or you did need capital funding after your founding, indicating you also need it now or will soon.