In the 2012 elections, all 435 House seats were contested. According to Ballotpedia, there were 42 incumbents who retired, leaving 393 seats to be contested by incumbents.
13 incumbents were defeated in the primary elections (Ballotpedia).
22 incumbents were defeated in the general election, 10 Democrats and 12 Republicans (Politico).
That makes for 358 incumbents reelected of the 393 who were running (or 35 House incumbent losses, depending on how you want to look at it), making a reelection rate for 2012 of 91%. This is about 2% lower than the historical average since 1954.
Also, a 91% House reelection rate for 2012 is the exact same reelection rate for the Senate this year, where 21 of 23 incumbents were reelected.