African Energy
13
Solar, gas, or
heat pumps?
By HydraTherm
We’re all trying to do our bit for the environment
by saving water and electricity. And since hot
water costs can comprise up to 60% of our
electricity bill, it makes sense to look at water
heating options that can reduce the load on your
wallet and your meter.
Due to the South African National Standard
10400-XA 2, a maximum of 50% of a new
building’s water heating can come from
an electrical resistance element — in
other words, all new buildings should have
half their electrical needs supplied by
alternative energy sources.
So, what are the options? The best are a
solar system, a gas water heater, or a heat
pump. When sized correctly, a solar system
has the potential to generate hot water at
virtually no cost, provided you don’t need
to use a backup electric element. Sunshine
provides one eight-hour heating period every
day and most hot water usage occurs in the
morning and in the evening. It is therefore
advisable to double the size of the water tank
when replacing a conventional geyser with
a solar system, to ensure there is 24 hours’
worth of water stored. Even so, the downside
is that your water will be lukewarm or cold
on very overcast days.
If you use a backup heating supply (whether
gas or electricity) to warm the water when
there isn’t enough solar power to do so, you
will incur the running costs associated with
that. This cost works out to about the same
as the annual average running cost of a heat
pump system. Heat pumps use electricity
to generate hot water, but almost 70% less
electricity than a conventional electric geyser.
Certain gas water heaters work without any
mains electricity supply, and provide hot
water no matter the weather conditions. But
compared to solar and heat pump systems,
gas has a relatively high running cost.
Taking running costs and availability of hot
water into account, a heat pump looks like
the best option; yet, of the three options, it is
the one with which South Africans are least
familiar.
A heat pump is a bit like a reverse-action
air conditioner. Where the air conditioner
transfers heat from the air inside a room to
the atmosphere outside, a heat pump trans-
fers heat from the air around it to the water
in its geyser. Its application has significant
benefits for the environment and consumers’
pockets. PA
“All new buildings should have half their electrical
needs supplied by alternative energy sources.”
www.plumbingafrica.co.za
August 2017 Volume 23 I Number 6