It is mentioned in
in a long Hadith that the Prophet (peace be upon him) said: (Part No. 7; Page No. 238)
Perform (supererogatory) Salah in your homes; the best Salah performed by a person is that offered in his home, except the obligatory Salah.
There is also the Hadith saying:
The best Salah of a person is that which he offers in his home except the obligatory Salah.
May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.