Google Sheets Optimization (rewrite formula to calculate sum based on multiple creteria)

I am trying to generate a table based on number of hours spent per month and per project for employee timesheets. The entry is done on the "Project Hours" page and the table on the "Summary" genarated automatically each time employee makes an entry. Each employee can enter time upto 3 projects per day. Here is the link for the sheet: [login to view URL] I have created some formulas to generate the table, they all work but my problem is the calculation time. It is takes too long to recalculate each entry. I have tried following formulas: 1. SUM(FILTER()) 2. SUMIFS() 3. SUMPRODUCT() Sum(filter() works the fastest among others, but still slow since it is a huge table (150rows by 72 columns, which may also grow in the future). The formula that I am using on cell C4 is as follows: =IFERROR(SUM(FILTER('Project Hours'!$D:$D; 'Project Hours'!$C:$C=$A4; 'Project Hours'!$A:$A<=C$2; 'Project Hours'!$A:$A>=C$1));0)+IFERROR(SUM(FILTER('Project Hours'!$F:$F; 'Project Hours'!$E:$E=$A4; 'Project Hours'!$A:$A<=C$2; 'Project Hours'!$A:$A>=C$1));0)+IFERROR(SUM(FILTER('Project Hours'!$H:$H; 'Project Hours'!$G:$G=$A4; 'Project Hours'!$A:$A<=C$2; 'Project Hours'!$A:$A>=C$1));0) WOULD THERE BE AN ALTERNATIVE and FASTER FORMULA TO GENERATE THE TABLE? MAYBE WITH OFFSET and COUNTA FUNCTIONS. Any help is greatly appreciated.