On November 5, residents of Berkeley will vote on a ballot measure that proposes taxing the owners of buildings of 15,000 square feet or larger based on the amount of natural gas consumed each year. If passed, legal experts say this would be the first tax in the country to target the use of a specific fuel source for buildings. City officials estimate that the tax would apply to over 600 buildings in Berkeley and generate $26.7 million during its first year, an amount larger than the city’s annual sales tax revenue. Of those funds, 90% would go toward retrofitting homes and buildings in the city with electric HVAC and appliances, and 10% would go toward city administrative costs.