A downhole heating apparatus includes a gas separator, a downhole heater, a thermal barrier and lower and upper perforated tubing joints being vents. The thermal barrier retards fluid and heat from flowing between a lower annulus of a wellbore and an upper annulus of a wellbore. The thermal barrier is formed from one or more thermal barrier subcomponents. The downhole heater is an electrical heater. The thermal barrier and lower and upper perforated tubing joints includes one or more vents.