Ahmad and Muslim relate from Jabir that the Messenger of Allah said: "If one of you offers his prayers in the Mosque then he should make a portion of his prayers in his house, as Allah has made his prayers in his house a means of betterment (for him)."

Ahmad records from 'Umar that the Messenger of Allah said: "The nawafil salah of a man in his house are a light; whoever wishes should lighten up his house."
'Abdullah ibn 'Umar reports that the Prophet sallallahu alehi wasallam said: "Make some of your prayers in your houses and do not turn your houses into graves." This statement is related by Ahmad and Abu Dawud.

Abu Dawud records from Zaid ibn Thabit on sound authority that the Messenger of Allah said: A person's salah in his house is better than his salah in my mosque, except for the fard salah."

These hadith prove that it is preferred to say one's nawafil prayers in one' s house since prayers in one's house are better than those that he performs in the mosque.

An-Nawawi says: "The Prophet Sallallahu alehi wasallam encouraged one to offer nawafl in one's house because then the prayers are more private and will have less of a chance of being done for show and will be free from defects that vitiate good deeds. Furthermore, this will be a blessing for the house as mercy and angels will descend on it while Satan flees from it."

Sayyid Sabiq

Fiqh Us-Sunnah Vol 1/2.2