| Cover Page | Jun. 26, 2020 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Jun. 26, 2020 |
| Entity Registrant Name | TUCSON ELECTRIC POWER CO |
| Entity Incorporation, State or Country Code | AZ |
| Entity File Number | 1-5924 |
| Entity Tax Identification Number | 86-0062700 |
| Entity Address, Address Line One | 88 East Broadway Boulevard |
| Entity Address, City or Town | Tucson |
| Entity Address, State or Province | AZ |
| Entity Address, Postal Zip Code | 85701 |
| City Area Code | 520 |
| Local Phone Number | 571-4000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0000100122 |
| Amendment Flag | false |
