There are 3 substations at Alton Towers. Each one takes a separate feed from the National Grid / local distribution network.
Some years ago, as long as at least 2 - or ideally all 3 substations were "up" for ride startup time of the huge energy consumers - namely the Flume, Rapids & Skyride, the park was fine. They still tried to start these 3 rides separately though due to the load the startup put on the system. Once everything was up and running, the park could technically run on just one substation. [This was a good 20yrs ago]. Since then they have added a Waterpark Hotel. Splash Landings itself won't be a huge drain on the electricity supply, but the waterpark drain will be huge.
Then add on all the other accommodation [electrically heated] and the addition of air conditioning to various places. The power supply / distribution across Alton Towers must be getting stressed, as to my knowledge no further substations have been added [there are no planning applications for any at SMDC - and even if it is the electrical distributor who needs the planning permission, it would show up with a ST10 4DB postcode search].
The Park was - possibly still are - on an un-metered supply, so as it's name suggests, a flat fee is paid irrespective of the energy used. It was very common to see heaters and lights left on 24/7 in workshops - even with notes next to them saying "Do not turn heater off". I would imagine that if they have not already gone out the window, un-metered supplies will be on their way out due to energy costs. (My monthly bill has gone from £76 to £120 in 3 months... and this is in Summer - and I had quite a big credit balance too).
When the park loses an electrical feed, the rides directly linked to the relevant substation tend to go down - at least temporarily.