Hi Kelvin,
Your question should be directed to a banker than real estate agent. Nevertheless, I'll give a shot at it.
Based on your loan amount and loan tenure, you may save up to $6.2K assume interest rate of 1% (down from 2.6%) over 6 years.
It is unlikely that the interest will remain low for 5 years. Therefore, assume interest rates to be 2% on average over 5 years, the potential savings would reduce dramatically to $2.5K.
After taking into consideration the legal fee (assume partial or no subsidy) and the risk of fluctuating rates for 5 years, I would advise you against any refinance unless you would like to restructure your loan to a longer repayment plan to reduce your monthly instalment i.e. pay more interest.
Hope this helps.
Best regards,
Jeron Lee
Jones Lang LaSalle Residential
Mobile/WhatsApp:
+65 90015060 Email: jeron.lee@jllassoc.com
Read More 
