Technology Snapshot & Benefits:
Solar water heating systems utilize the sun's energy to heat water for use
within a household or commercial property. Typically, solar water heaters are
made up of a storage tank, a solar collector, and a series of tubes, valves,
pumps and fluids that allow for water circulation. While certain systems may
function at higher capacities in warmer locations with greater sun exposure,
they do work in all climates. Different models are available for the home,
pools, and commercial properties.
There are two types of solar water heating systems - active and passive. The
former have circulating heat pumps while the latter do not. Active systems are
either direct (circulates water directly from collectors to the home) or
non-freezing heat transfer liquid
from the collector through tubes in the storage tanks to heat the surrounding
water). Passive systems, which are generally cheaper, but less efficient, are
typically either integral-collector systems or thermosyphon systems.
Integral-collector systems are best in warmer climates where temperatures rarely
drop below 32 degrees. Thermosyphon systems use basic water principles for
circulation by placing the outlet that goes to the home at the top and the
outlet that goes to the solar collector at the bottom. This allows for the hot
water (which rises) to go to the home and the cold water (which sinks) to be
circulated through the solar heater.
Storage tanks should be well-insulated to prevent heat loss. There are two main
types of storage tanks: two-tank systems and one-tank systems. Two-tank systems
have an additional conventional water heater attached for back-up while one-tank
systems have the conventional heater and solar heater integrated into the same
tank. Both systems provide back-ups in case the solar heat is insufficient on
any given day.
There are many different types of solar collectors and system set-ups. Consult
a local specialist and the online resources listed at the bottom of this page to
determine which type is right for you. For a basic overview of the different
Estimated Cost Savings:
While solar water heating systems are more expensive than conventional heating
systems, they can save you up to 50-80% on your water heating bills. The amount
of money you save depends on several factors, including the amount of water,
geographic location, fuel costs, financing incentives available, and the
system's performance. Installation and maintenance costs create additional
expenses, but these are still minimal when compared to overall savings.
To determine your estimated savings,
For information on financial incentives in your state, visit the
Database of State Incentives for Renewables and Efficiency.
As solar heating systems rely on the sun's energy to heat your household's
water, weather can sometimes create an issue by preventing adequate sunlight
from reaching the collector. However, the storage tanks often store enough hot
water to compensate for lapses in sunlight. Also, a conventional water heater
is attached to most systems to provide back-up in case there is not enough solar
These systems require a decent amount of maintenance to ensure they are working
properly. Check annually for problems like obstructions shading the collector,
failing pipe and storage tank insulation, and visual signs of wear or corrosion
on pipes and tanks. Consult a technician for routine qualified inspections.
For a complete list of recommended inspections,
It is important to take into account local temperatures when choosing a solar
water heater. While the heaters generally work for any climate, certain types
will not work in colder climates where temperatures frequently drop below
freezing because the outdoor components may freeze. Dry climates may also
require extra maintenance including cleaning the collector glazing as there is
no natural rainwater to cleanse it.
As solar water heaters use the sun as a source of energy, items blocking direct
sunlight may inhibit their proper function. Be sure to trim branches and trees
that may block sunlight.
Check local codes and regulations before installing a solar water heater. Some
areas require permits or special permissions before installation. See the
U.S. Department of Energy's Building Codes, Covenants, and Regulations for Solar
Water Heating Systems
for more information and to find the requirements in your area.
(Getting It Done):
Most solar water heaters require professional installation. For a list of solar
water heater companies,
If you decide to install your system yourself,
for a series of articles to help guide you through the process.
Before installing a solar water heater, make sure there is enough sunlight to
create noticeable energy savings. In the northern hemisphere, this typically
means installing the solar collector on a south-facing roof. In some cases,
they can be installed on roofs facing up to 90 degrees east or west and still
provide adequate heat. Consult a professional to find out what type of solar
water heater best suits your needs before purchasing. Also, remove any
obstructions that could potentially block sunlight from reaching the collector.
These include branches, satellites, tall trees, etc. Collectors should usually
be installed flat on the roof or according to the guidance of your installation
As a rule of thumb, solar collectors should be at least 20 square feet for each
of the first two family members in the house. For any additional family
members, add 8 square feet if you live in the Sunbelt region (south and
southwest U.S.) and 12-14 square feet if you live in more northern regions. For
example, if you live in the Sunbelt region and there are five people in your
house, your solar collector should be at least 64 square feet (20 + 20 + 8 + 8 +
8) to ensure adequate hot water supplies.
The size of the storage tank also correlates to the number of people in the
Small - 1-2 people
Medium - 3-4 people
Large - 4-6 people
It is important to purchase the right size solar collector and storage tank for
your system to properly heat enough water for every member of the household.
Many old hot water
heaters can be retrofitted with new solar technology. Ask your solar
technician or professional resource about retrofit kits when purchasing heater
Videos on This Topic:
Solar Water Heater Installation Part 1
(7:14) - In this video, watch the first part of a solar water heater
installation and learn about some of the basics of the technology.
Solar Water Heater Installation Part 2
(8:54) - Watch the second part of the installation video to learn about the
storage tanks and pipes and find out how much these systems can save you.
More Information on This Topic:
U.S. Department of Energy: Energy Savers - Solar Water Heaters
U.S. Department of Energy: Energy Savers - The Economics of a SolarWater Heater
U.S. Department of Energy: Energy Savers - Estimating a Solar Water Heater
U.S. Department of Energy: Energy Savers - Building Codes, Covenants, and
Regulations for Solar Water Heating Systems
Home Power - Hot Water Heaters
Solar Energy Industries Association - Factsheet on Solar Water Heaters
Florida Solar Energy Center - Solar Hot Water