Alternatives to such systems are gas heaters and district heating. Heating can be performed using sunlight combined with electrical heaters. Residential appliances such as furnaces, water heaters, and fireplaces can be upgraded. The company mainly manufactures washing machines, air conditioners, refrigerators, electric water heaters and gas cookers. Cast iron may be used for the heating vessel of domestic water heaters. Kerosene is also used extensively for home heating in portable heaters, especially farther north. Heat pumps are significantly more energy efficient than simple electrical resistance heaters. Indoors, exposure arises from cigarette smoke, and butane and kerosene heaters and stoves. Examples are electrical appliances, such as light bulbs, electric motors, and electric heaters. Electric showers may save energy compared to electric tank heaters, which lose some standby heat. Floor plans may also include details of fixtures like sinks, water heaters, furnaces, etc. Kerosene kept some market share by being increasingly used in stoves and portable heaters. Floor plans will also include details of fixtures like sinks, water heaters, furnaces, etc. Low power electric immersion heaters are common with home spas. The temperature is regulated by heat input from electrical coil heaters.