Should I buy a solar water heater or a heat pump?

[wily me]

Just received this e-mail. Makes for interesting reading.

The hard facts...
Electricity costs will increase again by at least 16% on 1 April 2012 - just two months away. By 2014, you will be paying R2.00/kWh. If you’re currently not using any sustainable energy solutions in your home such as heat pumps or solar for your water heating, then your average electricity consumption for a family of four is probably around R2000 per month. By 2014, in less than 24 months, that price is going to double to over R4 000 per month for the same amount of electricity – you will be spending around R50 000 of your hard earned salary per year for electricity!

What water heating solution should I choose?

With the price of electricity and the awareness of sustainable living sharply increasing, the popularity of renewable energy technology for heating water has climbed dramatically. But, as with many products on the market, there are many contradicting claims with regards to the different technologies used for water heating. Many of these claims and advertisements are nothing more than marketing speak and have no scientific research and facts behind them.
To help you in your decision making, we shed some light on specifically the saving that a homeowner will get from a solar water heater and a domestic hot water heat pump, based on proven academic research and studies. No marketing hard sell, just the facts...


Let’s start with the basics...

Solar water heaters use the radiation from the sun to generate heat. The size of the solar panel will determine how much energy can be collected from the sun. So if we for example have a 3sqm solar panel connected to a 150L geyser this might give us 150L of 60°C water at the end of a warm sunny day. But during cooler days with less sunshine it might only be able to heat the 150L to 35°C. In this case we would need an electrical element to heat the water further. If we have a solar panel that is only half the size (1.5sqm, we would only get out half the energy and an electrical element will need to do the rest.
Also if we assume we have 150L of 60°C water at the end of a warm sunny day and we use hot water in the evening, the water will most likely be cold in the morning. If you wish to take a shower in the morning, an electrical element will need to heat the water to a useable temperature. Solar water heaters do rely on electrical elements to provide hot water at all times. In our experience a high efficiency, properly sized solar system will typically provide up to a 50% saving on the energy required for hot water.

The reality is though that most solar systems in South-Africa are undersized and provide much less than a 50% saving on the water heating bill, despite the promised big savings by the company that sold it to them. It’s important to note that even if a high efficiency, properly sized solar water heater gives a saving of 50% on your water heating bill, this will not result in a 50% saving on your total electrical bill....unless the geyser is the only electrical device in your house.

Domestic hot water heat pumps work slightly differently. The heat pump uses a small amount of electricity to extract a lot of energy from the surrounding air. So a heat pump is also using the energy from the sun but only indirectly and so it can work day and night, winter and summer. The efficiency of a heat pump is called the COP. A COP value of 4 means that the heat pump produces four times as much thermal energy as what it uses electrically - in other words a 75% saving on the water heating bill. Using a conservative COP value of 3, a high efficiency heat pump like the ITS-4.7HDP takes about 1.5 hours to re-heat a 150L geyser – the most common geyser size in most households in South-Africa. This enables you to always have hot water at a fraction of the cost no matter when or how much water you use.


PRACTICAL CASE STUDIES

Case study # 1

Consider actual tests done with a family of four (two adults and two young children) that use water very conservatively. Measurements we have done on their 200L geyser show an average consumption of 16kWh/day.

Let’s first look at the solar water heating option...

On a 200L geyser most solar installers will put a 3sqm solar panel (flat plate or evacuated tube).
A top of the range high efficiency 3m solar panel that is perfectly mounted will provide a maximum thermal output of 7kWh/day
At an Eskom tariff of R1.25/kWh this equates to a saving of R24 640 over five years
A high quality solar system like this costs about R14000 for a retrofit system (connected to existing geyser) and about R21 000 for a complete system (solar panel and solar ready geyser) with the Eskom rebate already deducted.
Heat pump option...

With a conservative COP of 3 they save 10.66kWh/day and R37 500 over five years.
A heat pump will cost them about R13 000 fully installed with the rebate already deducted.
The heat pump will pay for itself in just over two years and provide a much bigger long term saving than a solar system.
Case study # 2

Family of four, more liberal with their water use and using an average of 30kWh per day on their 200L electrical geyser. Since a 200L geyser can only store 200L of hot water, connecting a bigger solar panel on will not necessarily result in a bigger saving. But they do have people in the house during the daytime and so we can go for a bigger 4sqm high efficiency panel.

Solar option...

The solar panel will give an average of 9.5kWh/day and a saving of about R33 400 over five years.
The cost of a 4sqm solar system will be about R24 000 for a complete system and will take about four years to pay for itself.
Heat pump option...

With a conservative COP of 3, they save 20kWh/day and R70 400 over five years.

The heat pump pays for itself in a year and five months.
Life expectancy is estimated at 10 years but we have systems that are running for more than 25 years and still going strong.
Unlike the solar option, a heat pump also requires virtually no change to your lifestyle and routine as it is not limited by the availability of sun for heating. Heatpumps can work 24/7.

Pricing


Our class-leading ITS heat pumps with patented loading valve technology, inclusive of plumbing and electrical Certificate of Compliance are available from:


4,7 kW Heat pump ……… R12,400.00

3,0 Kw Heat pump ……… R11,400.00

Our installation method is patented and no other heatpump provider is able to offer this technology. This means that with an ITS heatpump, you'll never experience cold water mixing with the hot water in your geyser and dramatically reduced geyser temperatures, unlike any other systems on the market. You can get cheaper systems on the market - but you won't achieve the efficiences or realise the financial savings you expected. This is one area where quality definitely trumps price and its worth doing your homework carefully to get the full cost saving potential that comes with our class-leading energy efficiency. Our ITS systems will deliver the highest possible cost savings for you for many years to come - guaranteed!


If you don’t have the cash available capital upfront, we have negotiated a very favourable monthly repayment plan with a reputable financial services company. Repayments are almost always less than what you will be saving on your electricity bill. Ask us about our monthly repayment plan and we’ll send you all the details and forms – finance applications approved between 30 minutes to 48 hours from submission of paperwork.
And our Heatsure maintenance plan means that for R49 per month, you’re covered for your annual service inspection to ensure your extended 5-year warranty at no extra cost, you have access to a 24-hour response time in the event of any loss of efficiency of the system at no extra charge for any parts covered under the warranty, and you will have the benefit of a planned and controlled service plan to ensure maximum savings

Call us today and find out how we can assist you to dramatically reduce your electricity costs, significantly reduce your impact on the environment and put your hard-earned money to good use on more important things! For every month that you delay, you're wasting hundreds of Rands that you could be putting back in your pocket every month

[AcidRaZor]

Heat Pump, geyser blanket and a decent timer with heat sensors would be good.

[etwylite]

I have a problem with any marketing exercise that purports to walk you through the numbers as they are invariably loaded in favour of a selected outcome.

So I question
1. Will the rate of R2/kWh be so?
2. Does the average family of 4 really spend R2000 pm on electricity currently?
3. Can i view the unit that is 25 years old?
4. A heat pump COP drops down to 1:1 at 0 degrees (generally in winter when you draw more hot water and need it most)

and the mention of lifecycle costs ie maintenance and life expectancy, a mechanical and electrical appliance (heat pump also needs refrigeration gas maintenance) compared to a passive device is going to be more costly in that regard.

Personally I have a combo solution of a solar geyser with heat pump backup.
We are 2 households (house and granny flat) of 2 adults each with duplicated appliances, fridge, washing machine and dishwashers.plus computers tvs etc etc
Also have a swimming pool that runs 4 hrs a day.
All cook on gas
all lights led or cfl.
Our avg monthly consumption is under 600kWh and supplied by eskom we pay about R450 per month all in for electricity.

Edit I can not agree that ANY house can use 30kWh a day on geyser heating. With a 3kW element this would imply 10hr a day operation and considering a geyser will generally heat from fully cold water (which it never is) to 55 degrees in under 2 hours this would imply 5 full cycles a day.

also consider that a heat pump life expectancy is half that of solar so factor in 2 purchases to 1 over the same period.

[Sinbad]

7kwh per day?! That is a complete lie.

My solar geyser boils. Literally you can hear the thing bubbling like a kettle.
I seriously doubt that's 7kwh per day.

My average electricity consumption is DOWN 500kwh per month. That's not 7kwh per day. And I still run the element at night (no timer)

Also, my solar geyser cost something like R8k after the rebate.

[chrisc4290]

Both. I have both. In summer the solar does 95% of the work. In winter the heat pump does 95% of the work. All a lot cheaper to run than a HWC

[Singularity1]

Heat pumps are more efficient at higher temperatures therefore heat pumps would be better suited to the Cape where winters are milder (compared say to Joburg). And solar water heaters would not be as effective as it's usually raining or overcast during winter.

[noxibox]

Heat pumps are more efficient at higher temperatures therefore heat pumps would be better suited to the Cape where winters are milder (compared say to Joburg). And solar water heaters would not be as effective as it's usually raining or overcast during winter.

I found it wasn't overcast nearly as often I'd thought it. Very thick cloud and rain seem to be two factors that completely cut off sufficient radiation. When the clouds are not dark grey enough still gets through to give a reasonable degree of heating. But in general in Cape Town I'd say expect two months of almost no benefit from the sun.

7kwh per day?! That is a complete lie.

My solar geyser boils. Literally you can hear the thing bubbling like a kettle.
I seriously doubt that's 7kwh per day.

My average electricity consumption is DOWN 500kwh per month. That's not 7kwh per day. And I still run the element at night (no timer)

Also, my solar geyser cost something like R8k after the rebate.

I think we used 3-5 kWh per day on hot water before having a solar panel. With the solar panel we get more hot water than we can use for at least 6 months of the year.