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Evacuated Tube Solar Versus Heat Pump Hot Water

Which is better in Tasmania

I want to start by saying outlining the comments on this page are based on my experience in the hot water industry over the last 10 years. We have sold hundreds of Evacuated Tube Solar hot water systems and well over 1000 Sanden heat pump hot water systems as well as two Atlantic hot water systems. When installing these hot water systems in most cases we have had to remove a hot water system to do so be it a regular electric element, solar, heat pump or gas hot water system. As a result of this experience, product knowledge & shared experiences of my clients I feel my comments here have some merit attached to them & it’s not just a sales pitch which I think if you keep reading you will agree.

Return On Investment

Before We Get Started - Is It Worth It?

One of the first questions I ask when a client approaches me for an efficient hot water system is how many people are in your house? This helps me identify what the client can potentially save by installing a hot water system. From data I have received from clients installing a Sanden heat pump hot water system will save on average $150 per adult per annum verses installing a regular electric element hot water system. E.g. two adults and two children in a typical house might save approximately $500 per year. There’s lots of variables on hot water consumption though. I sometimes shower twice per day and I don’t have many short showers. For those on tank water they might have shorter showers. Working with our two adults and two children example and lets say a $4500 Sanden installation you can see the return on investment is 9 years. You might think that’s not so great but bare in mind a regular hot water system costing say $1200 will never have a return on investment. Then consider if you need to spend $1200 replacing your hot water cylinder with a regular one then you should work out the return on investment on the Sanden based on $4500 less the $1200 which you would get no return on. This brings the return on investment for our example down to 6-7 years.


In summary the return on investment is best for households where there is a high volume of hot water used. Where there is only one or two people in a household I make my prospective clients very aware of this and in some cases I encourage them to instead consider installing solar power, installing a large regular hot water system on a timer & switching to the Time Of Use Tariff (93). You can read about tariff 93 here.

Evacuated Tube Solar Hot Water 
Or The Sanden Heat Pump?

Which Is The Better For Tasmanian Conditions?

Evacuated tube solar hot water is the most efficient solar hot water. C02 Heat Pump hot water systems (such as Sanden) are the most efficient heat pump hot water systems on the market. We sell both and make just as much profit selling either one. I would love to say I’m not biased but my experience which I have outlined above has made me so. I haven’t retailed an evacuated tube hot water system for several years but in the same time I’ve sold hundreds of Sanden heat pump systems.

Here are the reasons why:


Price – The Sanden is approximately $1500 less


Efficiency – When you buy an accredited solar hot water or heat pump hot water system it will qualify for STC’s which is a measure of efficiency. The Edson evacuated tube hot water system & the Sanden heat pump hot water system qualify for 32 STC’s when installed in Tasmania i.e. scientifically they are equally as efficient as each other - assuming the evacuated tubes aren't shaded. Something to bare in mind though is how they operate. The evacuated tube system solar cycle will trigger when the cylinder temperature is below 80C and the manifold sensor on the roof is 12C above that of the sensor in the bottom of the tank. So if your household uses a lot of water in the early morning/evening/night time in winter then there is a very good chance that your cylinder will need to re-heat using the back-up electric element which isn’t efficient.

The Sanden will trigger (unless the block out hours are set to off) when the tank sensor detects water at 45C. Even at ambient temperatures of 0C it has a co-efficient of performance (COP) of nearly 3 i.e. where a regular hot water cylinder will take 1KW of electricity it will give you 1KW of hot water, the Sanden will take 1KW of electricity and give you nearly 3KW of hot water. The COP of the Sanden increases to over 6 as the ambient temperature rises.

How Solar Hot Water Works
How Evacuted Tubes Heat Water
How The Sanden Heat Pump Works
How the Sanden Heats Water

Installation - The installation of an evacuated tube solar hot water system isn’t easy. Copper flow and return lines need to be run from the cylinder to the evacuated tubes and manifold on the roof. A sensor cable also needs to be installed between the manifold and the controller. A controller with a circulation pump needs to be installed next to the cylinder which will need an electricity socket to run it. Mounting the tubes & manifold onto the roof isn’t easy. A typical system has 30 evacuated tubes. The tubes need to be oriented within a 45 degree arc of true north & ideally on around a 67 degree pitch to get some performance in winter.

The installation of a Sanden heat pump hot water system is far simpler. Again a sensor cable as well as flow and return lines need to be installed between the cylinder and heat pump. A dedicated power supply needs to be connected to the heat pump which typically comes from your previous system. Far simpler than evacuated tubes.


Problems - Typical problems I have seen with evacuated tube hot water systems are: sensor cables breaking/corroding; pumps failing; controllers failing; tubes breaking; air elimination valves failing; over performance. Over performance can be a big problem particularly in summer. On a good summers’ day potentially the cylinder may be up to 80C temperature at 9am so the controller will stop the pump circulating water up to the manifold. The water in the manifold then gets trapped & gets much hotter. In the past an air elimination valve was installed on the manifold to let the water escape in the form of steam but these valves had a high failure rate so they were no longer provided in the kit. When the system is in this condition and a hot water tap is turned on the hot water that was on the roof mixes with cold water from your mains or rain water tank which can cause a kettle boiling type of sound in your cylinder and possibly some water hammer. The excessive pressure in the manifold on the roof can also lead to leaks in the joints on the manifold. The overperformance issue is chiefly in summer and when the household hot water demand is low.

The problems I have seen in the Sanden systems include: circulation pumps failing; circuit board failure; filters getting blocked due to poor water supply; air in the system. I’ve seen around 6 circulation pumps fail, these have been where the heat pumps have been installed on roof tops which I now refrain from doing. I’ve seen 3 circuit board failures, 2 due to huntsmen spiders crawling on the circuit board. This problem was only in the older models, the circuit board now has a protective enclosure. Filters getting blocked and air in the system are very simple maintenance issues which happen infrequently. Bare in mind out of the problems above we have sold over 1000 Sanden units in Tasmania.


Edson Evacuated Tube Solar Hot Water

Edson Evacuated Solar Tubes

Edson Solar Hot Water Cylinder

Edson Solar Hot Water Cylinder

Sanden Heat Pump Hot Water System

Sanden Heat Pump Hot Water System

Edson Evacuated Tubes

Aesthetics - To get the best out of an evacuated tube hot water system in winter & to de-tune it in summer to alleviate some of the overperformance the tubes should be pitched to at least 67 degrees. The tubes are 2M long which means if you can see your roof from then you will see a rather large structure on it. This structure casts quite a large shadow in winter which in turn can either reduce the available space for a solar power installation or decrease the solar power system production.

The Sanden heat pump looks like most other heat pumps except smaller. We usually install them on a wall bracket. No shading on solar panels.


Noise - Solar hot water systems make very little noise – aside from when they are over performing. You may associate noise with heat pumps but note the Sanden heat pump when running is just 37dB. Your typical heat pumps are over 60dB. That’s the difference between whispering and shouting.


Warranty - Both our Edson Evacuated tube system & Sanden Heat Pump systems have long domestic warranties. Freight & labour for the Edson is only covered for 12 months whereas its covered for the duration of the warranty on the Sanden heat pump & pro rata for the Sanden cylinder after 10 years.  For all the warranty details I suggest that you read the conditions in the warrnty/owners manuals.  The Edson warranty can be downloaded here, the Sanden owners manual can be down loaded here.  


Summary - I can’t think of any reason why I would choose a evacuated tube hot water system over a Sanden heat pump hot water system