The governing FIA said before final practice on Saturday that Ferrari and Haas had replaced the internal combustion engine, turbo charger and motor generator units in their cars' power units.
The changes exceed both driver's allocation for the season, triggering automatic penalties.
Sainz, the winner in Britain this month and fourth in the championship, already had a 10-place penalty after taking part in Friday practice with new control electronics.
The Spaniard, fastest on Friday, had been widely expected to drop further as a consequence of his car's engine blowing and catching fire in Austria two weeks ago.
"It's always difficult to overtake but he's got the pace, it can be a good race for him," Ferrari team boss Mattia Binotto told Sky Sports television.
"I think he's focusing on trying to have a good weekend and trying to minimise the disadvantage of having the penalties."
Ferrari are chasing their third successive win this weekend, with Charles Leclerc triumphant in Austria after Sainz's Silverstone success.
Haas also use Ferrari engines.
