Total Expense Ratio or TER is what the mutual fund insures to run the fund and market it to the masses. TER is at the fund scheme level and doesn’t not matter whether you invest lumpsum or with a SIP.
TER impacts you significantly because it has a bearing on the returns you make. The most important aspect is that Broker commissions are loaded onto the equity fund Regular Plans upto 1%-1.5%. If you go for Direct Plans, then there is no such commission loading. So the TER of a Direct Plan is much lower.
Therefore on a long term SIP of say 30 years, you will end up with 40% more on a Direct Plan vs Regular Plan since the TER is lesser. Please see this shareable illustration below:
