Active vs. Passive Solar Hot Water

A solar hot water heater is a green alternative to producing hot water in your home. There are two basic types of solar hot water heater: active and passive. Active solar water heaters use pumps and controls to circulate the water while passive systems use gravity and the natural circulation of water as it heats up.

Active vs Passive Solar Water Heaters

Active systems are typically more expensive, for they require more controls. In addition, passive solar water heating systems cost less to maintain due to having fewer parts that need to be serviced and replaced. Both systems utilize a solar collector and a water storage tank. Either water from the cold water intake valve is pump through the solar collector and back into the storage tank as with an active system, or cold water is heated in the collector and rises into the storage tank. Passive solar water heaters rely on the fact that hot water is lighter than cold water, thus rising when it is heated.

Although passive solar water heaters cost less to install and maintain, because they do not use pumps to circulate water, they will not work with every roof design. Additionally, if the weather in your region is prone to freezing, exposed water pipes could freeze and prevent the water heater from operating. An active solar water heater, despite being more costly, might be your only choice if roof design and climate play a prohibitive role.