Ask RiotACT: Switching from gas to solar hot water

Tommo83 2 April 2018 13

Ask RiotACT
Hello Riot land.

We are interested in switching our gas hot water system to solar.

Just interested to hear other experiences from people who may have done this recently. Any tips or recommendations? What sort of money did people save?


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13 Responses to Ask RiotACT: Switching from gas to solar hot water
Tim Thornley Tim Thornley 2:47 am 04 Apr 18

I made the switch a few years ago and got the gas disconnected. My system is SolarArc. It has a timer on the electric boost. We only need the boost for about 5 weeks either side of the shortest day in June plus the odd very cloudy few days in a row. Even then the sun does a lot of the work.

Sarelle Woodward Sarelle Woodward 6:12 pm 03 Apr 18

Don't do it. The HWS I got is known for not coping in sub zero temps. The tubes split and now I have a couple of thousand dollars worth of metal sitting on my roof. And the installers don't tell you.

    Julie Macklin Julie Macklin 10:15 pm 03 Apr 18

    I thought that was why the pump pumps hot water up to the tubes on cold night to stop this. Mine does this and after a few years no problems yet. Is yours pumping up to the roof at night?

    Tim Thornley Tim Thornley 2:48 am 04 Apr 18

    Agree with Julie. Your controler is not doing it's job

Mary Kingsford Mary Kingsford 10:21 am 03 Apr 18

Switched from electric hot water to solar hot water, cut my electricity bill in half.

Gaffable Gaffable 7:29 am 03 Apr 18

We had an electrician install a timer in our fuse box to control the operation of our electric booster. The timer switches the booster on automatically each morning for a set time period. In autumn and spring, we have the timer set to switch on the booster for 30 minutes from 4:30am. In wintertime, the booster comes on for two hours, from 3am to 5am. During summer we don’t need the booster at all. The brand of the timer is Theben and the model number is TR 608 top2 S:

Maya123 Maya123 12:43 am 03 Apr 18

Continuing from my previous comment.

Without a switch to turn the booster on and off, you would not know if the solar part of the unit is working. You might be using the electric booster as your only heat source. Very expensive electric hot water system that would be. That happened to me with my new solar system. The solar part of the unit had a broken wire and it wasn’t working. The water in the water tank was being heated 100% by electricity. It was only by insisting on a switch to turn the booster off did I discover this. Otherwise I would have had no way to know. When I turned the booster off my water didn’t heat. Therefore I knew there was a problem and had it fixed. It works as it should now. Fortunately I had the switch installed when my unit was new and so I wasn’t using only electricity for long.

Imagine if I hadn’t had that switch. I would not know the solar part wasn’t working and years later I would be thinking I was saving money, using less electricity, when all along all I had was an electric heater.

I do wonder how many people with boosters that can’t be turned off have broken units and are only running on electricity. They wouldn’t know, and this could have been happening for years. If you can’t turn off the booster, don’t be sure the sun is heating the water. You can’t tell if it’s the sun or if it’s only been working on electricity.

Maya123 Maya123 12:31 am 03 Apr 18

I have solar. I only need the booster for about one to two months a year. The sun heats the water for the rest of the year.
My system did not come with a switch to turn off the booster. An electrician installed one for me. The people who installed it argued that not being able to switch off the booster stops the chance of Legionnaires’ Disease and the like. The trouble with not being able to switch off the booster is that the water drops below 50C and the booster comes on; say after evening showers. Then next day is a hot, sunny day and the water would heat up in no time. With a booster that can’t be switched off electricity has already heated the water, defeating much of the reason for having solar hot water. Besides, for ten months of the year it’s rare that the water is not above 50C sometime during the day and for the two months it isn’t, it’s easy to turn on the booster. Make sure you have a switch.

bigred bigred 4:33 pm 02 Apr 18

We changed ours over to solar about 5 years ago from a gas system. Our previous system was on its last legs so we had to do something to avoid the middle of the night in winter fail. We weighed up continuous flow gas versus solar over a 20 year period making guestimates for where utility costs could go. Then we added in the warm inner glow factor from being increasingly green. Haven’t noticed an increase in electricity consumption from the booster being on two hours early morning and early evening. The gas useage hardly declined in relative terms – we had an old ducted heating system until recently. Over the recent Christmas we had up to 8 people in the house at any time and had no hot water shortages. On balance, I would do it again if the old system was about to fail.

A few things to note though. Modern solar hot water systems are quite complex compared to earlier models and as such not quite as reliable – expect to make a few warranty claims for small leaks or overflow valve failues etc. Also, once you install your new sysetm, you are subject to all the new plumbing regulations including lower pressure and temperature.

Capital Retro Capital Retro 10:02 am 02 Apr 18

Try mains electric with off-peak. According to the government all our electricity will be renewable in a couple of years so you can still feel warm and fuzzy about climate change without having your own (expensive) solar hot water.

    local1 local1 8:57 am 03 Apr 18

    My off-peak electric hot water system costs about $25/month, averaged out over the year in electricity costs, to run. About $300/year.

    Capital Retro Capital Retro 5:54 pm 03 Apr 18

    That’s about what mine costs to run and the unit should last for 20 years with no sacrificial anodes to replace and no cleaning. It doesn’t get much better than that.

JC JC 7:40 am 02 Apr 18

Of course you will save money. The question though is will you save enough to pay for the cost of the new system.

Frankly there are far too many variables to answer that simply.

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