The landlord's right to show the property depends on the wording of your lease. If you are unsure of the meaning of your lease or your rights and responsibilities as a tenant, you should consult an experienced real estate lawyer in your area.
Disclaimer: This answer is provided for informational purposes only, does not constitute legal advice, and does not create an attorney-client relationship. Actual legal advice can only be provided after completing a comprehensive consultation in which all of the relevant facts are discussed and reviewed.
The landlord's right to show up at any time depends on the terms of the lease but the landlord does not have the right to shut off electric service. Disconnecting electric service may entitle you to the equivalent of three months rent from the landlord. Call a landlord-tenant attorney as soon as possible.
No attorney-client relationship is created by answering questions in this public forum. If you wish to create an attorney-client relationship, you must contact me directly and sign a representation agreement. Answers are provided based on general ideas and an answer specific to your situation would require a review of all documents.