The Pipstrel Alpha Electro Trainer has an electric engine which weighs 11Kg.
How much would the engine of a comparable gasoline powered aircraft weigh ?
The Pipstrel Alpha Electro is an electric version of the Pipistrel Alpha Trainer which has a Rotax 912ul engine. The Rotax 912ul weighs 60kg.
For comparisons sake;
The Pipstrel Alpha Electro has a 11kg motor and 126kg of Lipo battery cells for a total of 137kg and about 1hr of flight time per charge.
The Pipistrel Alpha trainer has a 60kg engine and carries 35.5kg of fuel for a total of 95.5kg and 5-6hrs of flight time per tank.
flight time estimates are made assuming the planes are being used in a touch and go trainer role. At cruise speed flight times would be less.
EDIT for question in comments: The electric motor and Rotax engine both make 80hp. specs on the electric plane can be found here: https://www.aopa.org/news-and-media/all-news/2015/october/pilot/f_pipistrel and https://www.pipistrel-usa.com/alpha-electro/
Let me begin by saying I agree with the comment left by Ron, batteries are very heavy!
But to answer your question, Most medium sized trainers use a "360" engine built by either Lycoming or Continental.
A Lycoming O-360, an older, N/A engine fitted with a carburetor, weigh between 124.7kg and 137.4kg. Source.
Whereas when you "Kit Out" your Lycoming engine with a turbo and fuel injectors (TS-IO-360), they can weigh between 171.9kg and 184.6kg. Source.
If you're interested about what all the numbers and letters in an aircraft engine code mean, have a look at this Continental PDF documenting it all.