Accrual accounting requires adjusting payments for opening and closing balances to find the true expense.

Steps:

• Identify opening liability for electricity at start of 2022: not provided (credit balance given at 1 Jan 2023 suggests closing for 2022 is $800, but opening for 2022 unknown).
• Note payments during 2022: $400.
• Identify closing liability at 31 Dec 2022: ambiguous ($100 used "since year end" refers to post-2022 usage, not closing balance;$800 at 1 Jan 2023 implies closing $800 but conflicts with timing).
• Apply formula for expense: payments + closing liability - opening liability; cannot compute without opening liability.

Not enough information.

Final answer: Not enough information.