The benefits of chanting a manthra, and doing upasana to sandhya vary with the place where the upasaka seats himself. Yajnavalkya smriti says.
अग्न्यागारे जलान्ते वा जपेद् देवालयेऽपि वा।
पुण्यतीर्थे गवां गोष्ठे सिद्धक्षेत्रेऽथव गृहे॥
गृहेत्वेकगुणं प्रोक्तं नद्यादौ द्विगुणम् स्मृतं।
गवां गोष्ठे दशगुणं अग्न्यागारे शताधिकं॥
सिद्धक्षेत्रेषु तीर्थेषु देवतायाश्च सन्निधौ।
सहस्रं शतकोटीनां अनन्तम् विष्णुसन्निधौ॥
agnyāgāre jalānte vā japed devālaye'pi vā|
puṇyatīrthe gavāṁ goṣṭhe siddhakṣetre'thava gṛhe||
gṛhetvekaguṇaṁ proktaṁ nadyādau dviguṇam smṛtaṁ|
gavāṁ goṣṭhe daśaguṇaṁ agnyāgāre śatādhikaṁ||
siddhakṣetreṣu tīrtheṣu devatāyāśca sannidhau|
sahasraṁ śatakoṭīnāṁ anantam viṣṇusannidhau||
and Sankha echoes the same ideas.
If a man doing the upasana in his house gets one unit of benefit, it he performs the same in the banks of a river or a pond or seashore he gets double benefit. If the same is done in the stable of a cow he gets tenfold benefit. If it is done in a place where agnikarmas like agnihotra are performed and the aahavaneeya agni is kept, the effects will be hundred times. If it is performed in the hermitages of recluses and sages, or in pilgrimage ghats or in the temples of Gods, the effect will be one lakh million times and the effect will be beyond measure and infinite if the karmas as performed in the presence of Lord Vishnu. Think of Gaya Sraadhdham.. its greatness is because it is performed in the presence of Lord Janardhana.