The factors that determine the best system for your home

Have you been thinking about installing a solar water heater and not sure what systems are available and what’s best for your home?

There are a number of factors to be considered before deciding on a solar hot water system.  A plumber will recommend the best system for your home because solar hot water heaters should only be installed by a qualified plumber.

Their recommendation will be based on:

• number of people in your household
• the amount of water used
• when the water is used
• water quality
• the pitch of your roof
• the climate where you live

It is important that you understand how a solar hot water system works – as much as ensuring the plumber understands your household’s needs – so the right size is installed for your home.   If the storage tank is too small there is a risk you will run out of hot water occasionally or that the booster will need to be used more often. If your storage tank is larger than what your household needs, energy will be wasted in storing excess hot water.

Hot water usage is approximately 80 litres per person per day in Australia, on average.*  The types of appliances and features in your home, as well as how you use them, will affect your household’s hot water consumption.   Factors that can increase your hot water usage include:

• spa baths
• long showers
• living in a cold climate.

As a guide only, until you speak with a plumber, for an Apricus solar hot water system a broad indication of system sizes are:

• 1-2 Bedrooms: 22 evacuated tube solar collectors with a 250L tank
• 3-4 Bedrooms: 30 evacuated tube solar collectors with a 315L tank
• 4+ Bedrooms: 44 evacuated tube solar collectors with a 400L tank

*Solar Water Heater Guide, Department of Resources, Energy and Tourism, 2013

What is a solar hot water system?

A solar hot water heating system uses roof mounted solar collectors to absorb energy from the sun to heat water, which flows into the home.

There are various system options available, with a choice of:

• solar collector types (flat plate panels or evacuated tubes)
• boosting options
• gas (natural or LPG)
• electric
• system configurations (thermosiphon or split systems)

A complete solar hot water system usually includes:

• Solar Collector
• Hot Water Storage Heater
• Pump Station
• Controller
• Booster (Backup Energy Source)

What type of solar collectors are available?

The solar collector absorbs heat from the sun and uses it to heat the water that goes back into the hot water heater. There are two main types of collectors.

1. Evacuated Tubes

• These are a more recent and more efficient technology.
• Evacuated tubes consist of a series of glass tubes containing an inner water or heat pipe, surrounded by a vacuum.
• The round surface of evacuated tubes allows the sun’s rays to hit perpendicular to the surface for a larger part of the day, so there is greater solar collection.  This means they are more highly efficient for more hours in the day.
• They are particularly suited to colder climates and as their vacuum minimises heat loss and suited to  subzero temperatures
• More efficient in transferring heat
• Very durable – if a tube should break, it is easily and cheaply replaced.
• Provide excellent performance in overcast conditions
• Require a smaller roof area compared to flat plate collectors
• Apricus offers evacuated tube solar collectors as part of our solar water heater system. Evacuated tube solar collectors combine the high efficiency performance of evacuated tubes with the rapid heat transfer capacity of heat pipes to provide a collector that can operate efficiently in almost any climate.

2. Flat plates

Flat plate collectors work on copper pipes running through a glass covered collector, often connected to a water storage tank on the roof. The sun heats the copper pipes and the resulting hot water is thermo-siphoned out of storage tank

• They are most efficient when the sun is perpendicular to the surface.
• In cold climates, some flat plate collectors may suffer heat loss or be damaged by frost if not protected adequately.
• If the flat plates are damaged it can be expensive to have them replaced.
• These are the most common type of collector.  They work best when facing north.

Which solar collector is the most efficient?

When higher temperatures or higher performance is required in cooler weather, evacuated tubes have a big advantage over flat plate collectors.

Evacuated tubes are the most efficient.  They are also more durable and cheaper to repair should accidental damage occur.

To read more about the difference in performance for each collector type, download our Fact Sheet Evacuated Tubes v Flat Plate solar collectors fact sheet.