In Terran conflict there has been some changes to the shields, firstly the 125MJ from X3 has been replaced with a 200MJ variant. The other change is the 10GJ has also changed into a 2GJ shield.

Shields recharge using the ship reactor, so 3 x 5MJ will require 249kW worth of reactor to recharge at the maximum speed (1 minute). However say your ship only can develop 125kW, then the shields will take twice as long (so 2 minutes). Shields can not overclock, so the recharge times below are the very maximum speed that a shield can recharge.

Shield Size Strength Power usage Recharge time
1MJ Shield 1,000 33 kW 30.3 sec
5MJ Shield 5,000 83 kW 1 min
25MJ Shield 25,000 250 kW 1 min, 51 secs
200MJ Shield 200,000 1500 kW 1 min, 28 secs
1GJ Shield 1,000,000 2000 kW 9 mins, 15 secs
2GJ Shield 2,000,000 2000 kW 19 mins, 36 secs