(Providence, RI) -- National Grid is asking for a 19-percent electric rate increase for Rhode Island customers. The proposal, submitted to the Public Utilities Commission this week, would equal an average increase of nearly 19 dollars per month for a residential customer who uses five-hundred kilowatt hours. The utility company says the increase, which would go into effect in October and last until next March, is needed to pay for the higher cost of the purchase of electricity from suppliers.