Water Heating – Solar Thermal VS Traditional Heater Pump

Are you tired of paying gas or electricity to heat up your water?

Maybe you have thought about switching to solar for your home, and compared heat pump water heater vs solar thermal heater

In this comparison guide we break down the cost, system types and efficiency in easy to read format to help you out.

Bottom Line: Which One Is Better?

Solar thermal heating system is best for off grid use, while the electric gas heater system is best when connected to the power grid.

The reason why people compare these two options is for cost-saving and do their best to lower carbon footprint. To make this comparison simple, please check out our table below:

Solar Hot Water Heating System

Free hot water
Not all parts of the country can fully benefit from it
Great for off grid configuration
Gotta wait longer
Great DIY project
Definitely need a backup system
Cut electric bills by ~30-60%
Exposed to weather damages
No energy expense to create heat transfer
Poor performance during winter

Gas / Electric Water Heating System

Works in any weather condition
Costs more
Heats up fast
Heats up water pretty fast when needed
Not exposed to weather-related damages
Makes noise
No roof space needed
No special piping design
Use booster to keep the consistent water temperature

When Should You Consider a Solar Hot Water Pump?

For cost saving, solar is definitely the way to go to cut down greenhouse gas emissions and reduce gas & electricity bills.

For off grid home builders, solar is definitely the way to go.

When considering a solar water system, you will encounter different solar collector types yielding different efficiencies. The efficiency of a collector measures how well it converts radiation into usable heat.

Collector Types

Batch Solar Collector (Integrated Collector Storage ICS) - For cold climates

Bath collectors work well in remote locations without pumps or control systems. The insulated box heats the water and store it until drawn, and the water remains in the collector for long periods of time if the usage is low, which makes it hot.

Flat Plate Collector - Most common configuration

These consist of copper tubes fitted to flat absorber plates in series of parallel tubes connected at each end by two pipes (inlet & outlet manifolds). It's contained within an insulated box and covered up with tempered glass.

It's generally sized to hold 40 gallons of water, and two collectors can roughly provide hot water for a family of four.

Evacuated Tube Collector - Most Efficient

These are glass or metal tube containing the water surrounded by a larger glass tube to prevent heat loss. They work well in overcast conditions and can operate as low as -40F weather. However, it costs 2X as much per square foot as flat plate collectors

Circulation Systems


A direct solar hot water system work for some homeowners in the most southern parts of the US, where the water gets heat directly from the sun rather than an indirect system.


The indirect system collects solar energy then it gets stored in a special antifreeze fluid. When hot water is needed, the antifreeze is circulated into the hot water storage tank for use. (Indirect system is generally more expensive than direct system)


An Active system uses valves and pumps to move water from the collectors to the storage tank, and it's very common.


A Passive system doesn't need pumps. Natural convection moves water from the solar collectors to the tank as the temperature raises.

When Should You Consider a Heat Pump Water Heater?

A heat pump water heater has been around for a long time and is a great option if you just want a consistent hot water supply without experimenting with solar. People who have busy lives and have a decent income would rather focus their minds elsewhere rather than trying to save a buck by complicating their home configuration.

For most households, a traditional inside the home heat pump is more convenient.

Common FAQ

How Does a Heat Pump Water Heater Work?

A heat pump water heater works like a refrigerator in reverse.

In layman's terms without digging too deep into thermodynamics

Referenced Energystar.gov
  1. The compressor cycles the surrounding air and transfers it inside the electric heating elements
  2. Warm air is used to increase its temperature
  3. Heat flows through the condenser coil filled with hot refrigerant heats the water in the tank.

How Does a Solar Powered Hot Water Pump Work?

Referenced Solar Water Pump Technology Roadmap

A solar hot water pump works by converting sunlight into heat energy.

  1. The sunlight energy heats the water in the solar collectors connected by tubing (heat exchanger)
  2. The process called thermo siphoing increases the water temperature and it's made available to the house.
  3. The non freezing fluid cycles back to the collector

Main Takeaways

  • Solar thermal water heating system is great for off grid use
  • Solar water heater saves tons of money, basically using free sunlight energy to heat up water
  • Rooftop solar heater are exposed to weather damage
  • Traditional hot water heater pump works consistently regardless of weather condition
  • Hot water heater pump heats up water way faster for people with busy lives & don't care for saving a buck

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