Playing at the National Hockey Stadium in Bukit Jalil, UniKL who had lost their opening match 2-1 to Sapura, scored off a first minute penalty corner.
Najmi Farizal's flick gave them the lead, but Shahril Saabah drew level for Tenaga in the 27th minute only to see Nor Aqmal Gaffar (41st) give the Universiti side the lead again.
The match went into high gear after that and Azril Misron (57th) gave Tenaga a lifeline at 2-2, and the winner was claimed by Ramadan Rosli off a field attempt in the 58th.
It was Tenaga's second win, as they had beaten Maybank 2-1 last weekend.
Tenaga have six 2016 Project players, while UniKL have 10 juniors.
"UniKL are a team which plays high press for the entire game, and patience win us the game as we know that they can't keep up the momentum for 60 minutes.
"I'm very proud of my players, as they showed that local players can play good hockey and win matches as well," said Tenaga assistant coach M. Kaliswaran.
UniKL coach Arul Selvaraj blamed the crumble on accountability: "There was no accountability in the last quarter as tiredness crept into my players game and this is an area which I have been working on without success.
"Anyway, even in defeat Im proud to say that there were 16 2016 Project players on both sides and they did show some flare."
Arul is also the Project 2016 squad, which is preparing for the Junior Asia Cup in Kuantan in Novemner. The Cup is a Junior World Cup qualifier, with four teams from Kuantan qualifying for New Delhi next year.
RESULTS: Premier Division: Tenaga Nasional 3 UniKL 2, Maybank x Terengganu HT x, KL Hockey Club x Sapura x.
Division One Group A: MSP-YP-SSP 0 TNB Thunderbolts 2, MSNT-THT 1 MBI 0; Group B: PKS-KPM 4 Nur Insafi 4.
Women's Group A: ATM Pernama 1 The Cops 0, Penang Juniors 0 Politeknik 2, MSN Kedah 1 PKS KPM 3.
SATURDAY: Division One Group A: Masum USM v BJSS (KLHA, 5pm); Group B: UniKL Young Guns v Politeknik (National Stadium I, 5pm), UiTM v SSTMI ((National Stadium I, 7pm), ATM Airod v Nur Insafi (Tun Razak, 5pm).
Women's Group B: SSTMI Thunderbolts v KL Sukma (Taman Daya I, 5pm), Manjung v PKS-KPM (Azlan Shah, 8pm), MSN Kedah v UiTM Lions (Padang Serai, 5pm).
SUNDAY: Premier Division: Maybank v Sapura (National Stadium II, 6pm), UniKL v KL Hockey Club (National Stadium II, 8pm), Tenaga Nasional v Terengganu HT (National Stadium I, 8pm).
Division One Group A: BJSS v MBI (KPM, 7pm), MSN-THT v TNB Thunderbolts (Batu Buruk, 7pm).
Group B: UniKL Young Guns v SSTMI Thunderbolts ((National Stadium I, 4pm), ATM Airod v PKS-KPM (Tun Razak, 5pm), UiTM v Politeknik (National Stadium I, 6pm).
Women's Group A: MSN-PHT v Politeknik (batu Buruk, 5pm); Group B: Manjung v UiTM Lions (Azlan Shah, 5pm).