Solar hot water system - 5 years down the track

hot frog wrote:

It's now five years since we installed a solar hot water system. For anyone
thinking of getting one, here's our experience so far:

Electricity consumption Jan1995 - Dec1999: 23271 kWh
Electricity consumption Jul 2000-Jun 2005: 3757 kWh
Reduction: 19514 kWh
Reduction as %age: 83.9%
Reduction in electricity bill: ~$1400
CO2 reduction: ~27 tonnes

The system cost $1070 more than just replacing the electric one, so as an
investment it has now overtaken a term deposit paying 5% interest after tax.
The break-even point occurred a year earlier than initially predicted due to
increases in the cost of electricity, including introduction of the GST,
that I forgot to take into account. (If we'd had to pay GST on the system,
we would probably still be ~18 months from breaking even, and if it weren't
for the $750 government rebate, we would still have 4 or 5 years to go.)

From now on, if the above figures are any guide, the reduction in our
electricity bills will be equivalent to a 20%+ return, tax free, on our
'investment', while reducing CO2 emissions by over 5 tonnes per year.

BTW, if you were trying to achieve a similar reduction in CO2 by riding a
bicycle instead of driving a 1.6 litre car, you would have to pedal about
45,000 km per year. :-)

Anyone interested in the details of our system can find them in the archive
by searching for posts by 'hot frog' with the word 'solar' in the title:
http://groups-beta.google.com/groups...thors=hot+frog

Hope this is of some use to someone considering a solar HWS.

That's great to know, I have to replace the hot water system (gas
continuous flow) with something new soon.

I'm a bit dubious about some of your calculations though. Looks like you
may have overestimated your CO2 savings on the electricity and
underestimated the savings by bicycle.

My info says that 1kWh produces 0.95kg CO2 so your savings over 5 years
are 18.538T or 3.707T per year.

A 1.6L Ford 2004 (petrol/automatic) produces 179g CO2 per km. To save
3.7T you need to replace a mere 20700km per year with bicycle journeys!

Peter

--
Peter McCallum
Mackay Qld AUSTRALIA

On Mon, 18 Jul 2005 10:40:33 +1000,
(Peter McCallum) wrote:


A 1.6L Ford 2004 (petrol/automatic) produces 179g CO2 per km. To save
3.7T you need to replace a mere 20700km per year with bicycle journeys!

You also have to make the car (and the bike!) which isn't free.

On 2005-07-18, Carl Brewer (aka Bruce)
was almost, but not quite, entirely unlike tea:
On Mon, 18 Jul 2005 10:40:33 +1000,
(Peter McCallum) wrote:


A 1.6L Ford 2004 (petrol/automatic) produces 179g CO2 per km. To save
3.7T you need to replace a mere 20700km per year with bicycle journeys!

You also have to make the car (and the bike!) which isn't free.

And the hot water system.

Why do people always forget about the costs of
manufacturing/transport etc?

--
TimC
"The lights went out in his eyes for absolutely the very last time
ever." -- DNA (Mar 11, 1952 - May 11, 2001)

Peter McCallum wrote in message
u...


That's great to know, I have to replace the hot water system (gas
continuous flow) with something new soon.

Gas hot water systems are already far better than electric ones in terms of
CO2 emissions, so your potential CO2 reduction won't be as great.
Gas-boosted solar systems are excellent of course, but they weren't an
option for us so I didn't look into the economics.

I'm a bit dubious about some of your calculations though. Looks like you
may have overestimated your CO2 savings on the electricity and
underestimated the savings by bicycle.

My info says that 1kWh produces 0.95kg CO2 so your savings over 5 years
are 18.538T or 3.707T per year.

I was working on a figure of 1.381kg CO2/kWh, which I found years ago on a
Sustainable Energy Authority Victoria website. I have now discovered that
Victoria uses a lot of brown coal which generates more CO2 per kW than the
black coal used in Queensland. The exact figure would also depend on
transmission losses I'd imagine.

"The Australian Renewable Energy Site" seemed to use a figure of 1.0kg
CO2/kWh for Brisbane in one of their case studies, so I've corrected my
spreadsheet accordingly. It's a bit disapponting that our GHG reduction is
less than we thought, but at least that number makes the calculations a lot
easier to do in your head. :-)

A 1.6L Ford 2004 (petrol/automatic) produces 179g CO2 per km. To save
3.7T you need to replace a mere 20700km per year with bicycle journeys!

Is that all. :-)

My estimate was based on data from an Energex brochure, which equates
1000kWh to 288 days use of a car with a 1.6L engine, driven 14700km/year.
So 19514kWh is equivalent to 5620 days or 15.4 years use of the car, or
226341km, or 45268km/yr for 5 years.

Energex probably chose the most efficient 1.6L vehicle it could find to make
the comparison look good. :-)

Nevertheless, it shows that a single solar hot water system can reduce CO2
emissions by an amount that would be very hard to match by cutting down on
the use of your car.

Peter McCallum wrote in message
u...


That's great to know, I have to replace the hot water system (gas
continuous flow) with something new soon.

Gas hot water systems are already far better than electric ones in terms of
CO2 emissions, so your potential CO2 reduction won't be as great.
Gas-boosted solar systems are excellent of course, but they weren't an
option for us so I didn't look into the economics.

I'm a bit dubious about some of your calculations though. Looks like you
may have overestimated your CO2 savings on the electricity and
underestimated the savings by bicycle.

My info says that 1kWh produces 0.95kg CO2 so your savings over 5 years
are 18.538T or 3.707T per year.

I was working on a figure of 1.381kg CO2/kWh, which I found years ago on a
Sustainable Energy Authority Victoria website. I have now discovered that
Victoria uses a lot of brown coal which generates more CO2 per kW than the
black coal used in Queensland. The exact figure would also depend on
transmission losses I'd imagine.

"The Australian Renewable Energy Site" seemed to use a figure of 1.0kg
CO2/kWh for Brisbane in one of their case studies, so I've corrected my
spreadsheet accordingly. It's a bit disapponting that our GHG reduction is
less than we thought, but at least that number makes the calculations a lot
easier to do in your head. :-)

A 1.6L Ford 2004 (petrol/automatic) produces 179g CO2 per km. To save
3.7T you need to replace a mere 20700km per year with bicycle journeys!

Is that all. :-)

My estimate was based on data from an Energex brochure, which equates
1000kWh to 288 days use of a car with a 1.6L engine, driven 14700km/year.
So 19514kWh is equivalent to 5620 days or 15.4 years use of the car, or
226341km, or 45268km/yr for 5 years.

Energex probably chose the most efficient 1.6L vehicle it could find to make
the comparison look good. :-)

Nevertheless, it shows that a single solar hot water system can reduce CO2
emissions by an amount that would be very hard to match by cutting down on
the use of your car.

hot frog wrote:

Peter McCallum wrote in message
A 1.6L Ford 2004 (petrol/automatic) produces 179g CO2 per km. To save
3.7T you need to replace a mere 20700km per year with bicycle journeys!

Is that all. :-)

My estimate was based on data from an Energex brochure, which equates
1000kWh to 288 days use of a car with a 1.6L engine, driven 14700km/year.
So 19514kWh is equivalent to 5620 days or 15.4 years use of the car, or
226341km, or 45268km/yr for 5 years.

Energex probably chose the most efficient 1.6L vehicle it could find to make
the comparison look good. :-)

Nevertheless, it shows that a single solar hot water system can reduce CO2
emissions by an amount that would be very hard to match by cutting down on
the use of your car.

Add the energy used in manufacture of a car is also an issue. I've heard
various estimates from a low of 10% of the total lifetime energy use, to
high estimates of more than 50%. Then there is the cost of provision of
and replacement of roads and all the other ancillary energy use for
private motor transport.

You should also consider that you only have one hot water system per
family but many households would have more than one car.

In any case we all need to be cycling/walking as much as possible to
reduce our environmental impact.

Peter

--
Peter McCallum
Mackay Qld AUSTRALIA

On 2005-07-19, hot frog (aka Bruce)
was almost, but not quite, entirely unlike tea:
I was working on a figure of 1.381kg CO2/kWh, which I found years ago on a
Sustainable Energy Authority Victoria website. I have now discovered that
Victoria uses a lot of brown coal which generates more CO2 per kW than the
black coal used in Queensland. The exact figure would also depend on
transmission losses I'd imagine.

I've heard you usually expect 30% efficiency for obtaining energy from
electricity, factoring in transmission losses. I've got no cites for
this though, so just heresy.


--
TimC
Black holes are where God divided by zero. -- Steven Wright

On 2005-07-18, Peter McCallum (aka Bruce)
was almost, but not quite, entirely unlike tea:
hot frog wrote:

It's now five years since we installed a solar hot water system. For anyone
thinking of getting one, here's our experience so far:

Electricity consumption Jan1995 - Dec1999: 23271 kWh
Electricity consumption Jul 2000-Jun 2005: 3757 kWh

Just goes to show how much of your electricity bill goes to hot water,
and why Australians are stupid for using electricity and not gas to
heat their water. Gas is at least 3 times more efficient than
electricity, and judging from my experience with gas and electricity
bills, probably more (I'm taking cost here as a proxy for resource
use).


--
TimC
NOT A CHANCE! I know for a *fact* the kittens aren't frightened
by temporal anomalies. Clock watching simply ain't their bag.
John Schmidt in ARK

TimC wrote

Just goes to show how much of your electricity bill goes to hot water
and why Australians are stupid for using electricity and not gas t
heat their water. Gas is at least 3 times more efficient tha
electricity, and judging from my experience with gas and electricit
bills, probably more (I'm taking cost here as a proxy for resourc
use)

I hear you, Tim, but how much does it cost to have gas installed? Yo
would probably find that a lot of people can't afford to have ga
installed when they build a house and leave it for later (or maybe the
just don't care). That's what we're doing anyway. I HATE cooking usin
my sh!tty electric stove and it pains me just how inefficient they are.

I was surprised to get our latest electricity bill. $231 as opposed t
our usual $140 - $150. This was our first full three month bill in ou
new house, which is twice as big as our old unit. Anyway, in the unit
the hot water system was about half the size of the one we now hav
(probably only designed to cater for two people) and we ran those powe
saving lights. As much as we've been thinking we'd put those powe
saving lights in, it might not make that much of a difference now tha
I think about it (ie. the hot water system being huge is probably wha
sucks power). We do pay more because we're on a 'green' energy packag
though, but that's not supposed to cost a whole lot more..

??

Lott

--
LotteBum

On 2005-07-20, LotteBum (aka Bruce)
was almost, but not quite, entirely unlike tea:
I hear you, Tim, but how much does it cost to have gas installed? You
would probably find that a lot of people can't afford to have gas
installed when they build a house and leave it for later (or maybe they
just don't care). That's what we're doing anyway. I HATE cooking using
my sh!tty electric stove and it pains me just how inefficient they are.

Heh. You can't cook stirfrys on electricity, that's for sure. Bad
memories of that particular electric wok -- I went home to show off my
l33t stir-fry skills to mum, and then discovered why her stir-frys
always sucked so much. I ended up manually being the thermostat,
except, not a very good one (yay hysteresis -- 100 degrees then 300
degrees).


I was surprised to get our latest electricity bill. $231 as opposed to
our usual $140 - $150. This was our first full three month bill in our
new house, which is twice as big as our old unit. Anyway, in the unit,
the hot water system was about half the size of the one we now have
(probably only designed to cater for two people) and we ran those power
saving lights.

I don't think a bigger hot water service is any less efficient than a
smaller one. They don't waste that much heat - most of the energy
burnt will actually be used to heat water that goes through the taps,
very little makes it out through the insulation etc.

As to the lights -- only add them to rooms where you expect the lights
to be on at least say 5 hours a day -- and continuously -- they don't
like being switched off and on too much. Remember cost can be thought
of as a proxy for the amount of energy that went into manufacture --
there are reasons why energy saving lights are $15, and globes are
$0.60 -- circuitry and flourescing surfaces take far more energy to
manufacture than a glass globe in an depressurised inert atmosphere.

As much as we've been thinking we'd put those power
saving lights in, it might not make that much of a difference now that
I think about it (ie. the hot water system being huge is probably what
sucks power). We do pay more because we're on a 'green' energy package
though, but that's not supposed to cost a whole lot more...

And no electric heaters, I hope?

--
TimC
double value; /* or your money back! */
short changed; /* so triple your money back! */
-- Larry Wall in cons.c from the perl source code