INTRODUCTION To inform policy making under the proposed The Control of Tobacco and Electronic Delivery Systems Bill, we compared annual costs of using e-cigarettes versus cigarettes, and estimated revenue from e-cigarette taxation. METHODS We extracted e-cigarette retail prices from 231 South African e-cigarette vendor websites. We compared annual costs associated with daily cigarette smoking (self-reports from daily smokers in the 2018 South African Social Attitudes Survey, SASAS) versus daily e-cigarette use (based on cumulative costs of consumables plus device costs). We estimated revenue from excise tax if e-cigarettes were taxed at 75% (the rate proposed by the government) and 37.5% (half of the government's proposal as a hypothetical scenario) of the cigarette excise rate. We applied the different rates to e-cigarette consumption in 2018 SASAS and projected for 2021. RESULTS Mean annual cost associated with daily use was ZAR 6693 (US$460.32, based on an exchange rate of about 69 US$ to 1000 ZAR) for manufactured cigarettes; for e-cigarettes, this ranged from ZAR 8574.69/year (with price minimizing strategies) to ZAR 19780.83/year (retail products exclusively). Expected revenue from e-cigarette excise tax at 75% of the cigarette tax rate was up to ZAR 2.20 billion (95% CI: 0.96-3.44). If taxed at 37.5% of the cigarette tax rate - half of the government's proposed rate - the projected revenue was up to ZAR 1.10 billion (95% CI: 0.48-1.72). Of the projected revenue from e-cigarette excise tax at 75% of the cigarette rate, the portion attributable to hardware (device and batteries) was 61% (ZAR 1.35 billion), while the portion attributable to e-liquid was 39% (ZAR 0.86 billion). CONCLUSIONS Calculated daily costs were higher for e-cigarettes than cigarettes. We recommend an e-cigarette excise tax. The government's proposed tax rate may reduce youth e-cigarette access, while allowing adult smokers wishing to switch exclusively to e-cigarettes to reduce their tobacco-related harm.