Renewable Hot Water Systems: Solar Collectors and Heat Pumps

Water heating is an everyday activity in most homes, especially in cold regions. However, commercial buildings like restaurants and hotels do a lot of water heating. Usually, when water heating is mentioned, the first methods that come to mind are; combustion and electric resistance. And these methods take up a big part of the building’s energy. However, solar collectors and heat pumps provide the solution to energy inefficiency and an all-round green solution.

Although the cost of combustion heating is relatively low, it involves the burning of fossil fuels which can be harmful to the health of the environment. Thus negatively affecting the quality of air in the environment. Electric resistance, on the other hand, do not produce physical emissions, but the cost of installation and operation are usually high.

Save Energy Cost With A Renewable Hot Water System.

As you would rightly guess, solar collectors, use sunlight, which is free and reaches its point of use by itself. Additionally, the installation of solar collectors on rooftops or other elevations requires a small pumping cost.

The working principle of heat pumps involves the gathering of thermal energy from the environment’s air to heat water. And as such, it indirectly uses the sun’s energy. Like resistance heaters, heat pumps operate with the use of electricity, albeit with over 50% reduction in energy consumption.

Energy statistic shows that 10% of overall in house energy consumption is associated with hot water. For multifamily homes, it is as high as 19% of energy consumption. Incorporating renewable heating methods like solar collectors and heating pumps will reduce the impact of “hot water energy” on the environment, and at a reduced cost.

Energy Savings: Solar Collectors Vs Heat Pumps

Solar collectors and heat pumps save energy, albeit in different ways. Let’s look at how they both achieve energy savings.

  • Solar collectors are in direct contact with solar energy. It absorbs this energy and gathers enough with the use of heat transfer fluids. And the heat exchanger converts this thermal energy to heat water without mixing. In hot climate regions, it is possible for solar collectors to heat water without the use of a heat transfer fluid.
  • Heat pumps save energy by absorbing thermal energy from outside air, and as such, can run anytime, even at night when there is no direct sunlight. Notably, the efficiency of heat pumps is directly proportional to the temperature of the outdoor air. In other words, there is a drop in efficiency when the air temperature drops. Therefore heat pumps can still gather thermal energy in the winter. The use of a defrost cycle aids the use of heat pumps during the winter.

Admittedly, solar collectors are sunlight dependent, hence, it cannot heat water in the cool of the evening (absence of sunlight). While, heat pumps do not depend on the presence of sunlight, and it can absorb energy from the outdoor air at any time, during the day or at night.

That said, you can incorporate the use of solar collectors and heat pumps to achieve maximum energy savings. This way, you can maximize the free water heating that comes with solar collectors in the presence of sunlight, while the heat pump covers for the solar collectors in the absence of sunlight.

Heat pumps can synchronize with onsite renewable generation systems to produce a greater energy-saving effect. The energy-saving capacity of heat pumps is evident in the fact that for every kWh of electricity used, it produces an average of 4KWh, depending on the type of heat pump. In other words, an electricity output of 100KWh will produce an average of 400KWh of water heating.

Heat pumps can serve as an energy storage system. When other renewable sources like solar panels, produce surplus energy, heat pumps can convert and store surplus energy in water. Using an insulated tank will ensure hot water can be kept hot for future use.


Solar collectors and heat pumps are green alternatives to conventional water heating systems. If you don’t have enough roof space, you can, air source heat pump is a viable option for you. You can mount your heat pump outdoor unit on walls as in air conditioners.

Is your available space hidden from sunlight? Heat pumps do not need direct sunlight to operate, making it the perfect option. However, solar collectors are inefficient without sunlight. For more insight on what will work best for your home, consult HVAC and MEP design firms.