Heat pumps vs solar heating

 Points of consideration Solar geysers Heat pumps
The way it works A solar collector, located on the roof, collects the sun's energy and transfers heated water to a storage tank, where it is stored until it is used. The tank can be located away from the panel (a pump is then necessary) or the  tank can be placed above the panel. Works like an airconditioner in reverse. It uses a small amount of electricity to extract heat from the surrounding air and then heats water with this energy.
 Types Three types of systems: direct systems, suitable only for frost-free climates, direct frost resistant sytems, and indirect systems, where water is heated via a heat exchange mechanism - suitable when area is prone to frost, or in hard water areas.  Two types of configurations: integrated systems where the entire system is a single unit with a storage tank and heat pump, and split systems, where the tank is separated from the heat pump.
 Rebate Eskom rebate. Claims must be submitted after payment of the system, and rebate is paid within approximately 8 weeks from the date of receipt. Eskom rebate when bought from listed supplier. Rebate is paid to supplier - no need to wait to apply. Rebate available until March 2013.
Initial cost, including Eskom rebate  Between R12 000 and R18 000  Between R7000 and R12500
 Potential saving

15 - 20% of electricity bill. Saving comparable to that of a heat pump for households with up to 4 persons.  For larger households, bigger tanks are recommended. 

Up to 47% of  total electricity bill. Savings higher than with solar geysers in bigger households where hot water demand exceeds solar heater capacity.
 Running costs Free, when sun is shining. At night, or when it is cloudy or rainy, electricity backup may be necessary, which decreases saving potential. Typically consumes 1 unit of electrical energy for every 2.5 - 3.5 units of heating provided - a saving of 60% - 70%  in comparison to conventional electrical resistance heating.
 Life expectancy  20 years  10 - 15 years

 Investment recovery period

3  - 4  years - the larger the household, the shorter the period.  2 -3 years  - the larger the household, the shorter the period.
 Guarrantee Depends on supplier  Depends on supplier - between 1 and 5 years
 Efficiency measure SABS states it as  the Q factor (MJ/day) - the amount of energy absorbed  for one day of sunshine. Effiency is  given as a factor called COP.The colder the ambient air temperature and the warmer the desired hot water output, the lower the COP. COP of 2 - 3.5 common.
 Maintenance and service required

Wipe clean collector surface when dusty. Check system annually for best possible effeciency.

Keep evaporator clean from dirt and leaves. Check system annually for best possible effeciency.
 Water temperature  High  60 ºC maximum
 Availability of hot water Dependent on weather. At night and in bad weather backup with electrical heating element may be necessary. On cloudy days, 25%- 30% of the sun's energy still gets through, but the heat output is reduced.  Warm water, day and night, rain or shine - if there are no power cuts. Back-up power supply may be necessary if there are regular power cuts.
 Regulation of water temperature  Cannot be regulated.  A control panel allows water temperature to be set.
 Effect on water pressure May affect pressure in existing mixer taps.  None.
 Dependency on electricity Electricity back-up necessary if water usage exceeds capacity, and when there is no sun for prolonged periods - at night, during winter and on cloudy days. Electricity is necessary - generator backup may be  necessary during extended power cuts.
 Existing geyser Standard installation replaces existing electric geyser. Existing geyser can remain intact with pre-feed installation and a retrofit system.  Can be retrofitted to existing geyser.
 Time to install  Can be installed in a day.  Can be installed in half a day.
 Environmental advantage  Clean energy, which naturally reduces CO2 emissions and  carbon footprint. Energy efficient, with no greenhouse gas emissions.
 Safety  Tried and tested. Comply with SANS IP ratings for outdoor electrical installations.
 Damage risk Roof structure must be able to carry weight of system. Choose indirect system if area gets frost or water has a high mineral content.  Hail damage may occur, but it happens rarely with SABS approved system.  Built to be weather proof.
 Position On roof, facing solar north and an inclination angle of  latitude + 10 degrees for best results. Visible. Under eaves on the outside. Visible, but can be placed out of sight. 
 Noise levels  No noise. Comparable to air conditioning .
 Suitability for coastal conditions  Effects of corrosion may have an impact on the longevity of the system. Choose system designed for conditions.  Corrosion damage possible if not sprayed with protective layer.
 More about it - click on link Solar geysers  Heat pumps

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