Formula One is going through its biggest change in its history. It is the ending of the V8 era and the beginning of the turbocharged V6 era, and for the first time Formula One cars will use two forms of hybrid power. MercedesMercedes-BenzGermany, 1924 > present197 models
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and RenaultRenaultFrance, 1898 > present189 models
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have revealed the designs for their 2014 Formula 1 engines. Things have changed so much that they are no longer called engines; they are now power units. 

All of the power units combine a 1.6-liter direct-injected turbocharged V6  with regenerative braking and thermal energy recovery from the exhaust gases. The engines have a maximum redline of 15,000rpm. Power is still rated at 760hp, which is on par with the previous engines. The cars may carry 100kg less fuel than before, a 35% reduction, and fuel flow is limited to 100kg per hour. 

To make things even harder on the engine makers, development is prohibited during the season. Each driver is limited to five engines per season.

The truly new portion of the power units is the exhaust heat energy recovery. it would better be described as an electric turbocharger. The system puts a load on the turbine shaft to convert the heat energy of the exhaust gases into electricity. This is power is sent to the unit's battery where it is stored until needed. The system varies the load based on the air requirement of the engine, which means that it can slow it down in place of a wastegate or to accelerate it to compensate for turbo lag.

FerrariFerrariItaly, 1947 > present233 models
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is the only 2014 engine maker that has not yet officially unveiled its power unit.

You can watch a video showcasing the new Mercedes power unit below.