Our house doesn't use much elec. At least i think lol

We have gas stoves and gas geyset. In summer running two small airbnb units we use about 250-300units a month (believe thats 300kw?).

Problem 1: We use quite a bit of gas to hear up our water in the winter when it drops to about 5-8c outside in the mornings. The pipes are exposed outside so water is pretty damn cold. Pipe insulation seems costly at R100 per meter and we would need at least 50m. To help reduce our gas bill was thinking of installation of an ITS FP 2.0m² Vertical Flat Plate Solar Collector or black hdpe piping to preheat the water a bit?

For the house we are looking at a 6kw Lux power with a 5kw dyness battery and 6 to 8 panels. We think this might be fine for now. We use fireplaces for heat.

In saying this, is there a better cost effective solution besides doing the above mentioned water gas geyser preheater?

We dont have an electric geyser anywhere on the property.

Any advice be grateful.

Edited March 18, 20251 yr by sunset1

Well to preheat the water makes a huge difference in water temp in winter and gas consumption.

I have a 16l gas geyser for 2 bathrooms, It was connected straight inline with the hot water line to the taps, bypassing the electric geyser completely.

with this setup I used 9kg every 9 to 14 days depending on the season. My outside pipes is insulated with much cheaper pipe insulation, I saw the pipes in my roof was insulated with old cloth and rags bound around the pipes with twine, and that also works.

about 6 month ago I put my electric geyser back inline to preheat and feed the gas geyser, I set the geyser thermostat to 40 degrees and changed the element to a 2kw unit.

I use 4kw/h to pre-heat the water (150L) thats fed to the gas geyser, in the dead of winter with only the gas geyser heating the water I could not get the water temperature above 45 degrees.

now with the preheated water the temperature easily reaches 80 degrees in the summer(80 degrees is the geyser's cut out temp) and I have not seen the water temp below 55 degrees and the gas geyser is set to max water flow and min gas, and this have resulted in a 9kg gas bottle lasting 25 days plus....

I think if i had a spare electric geyser i would do something similar and add an extra panel or two to keep it warm...

Have you considered an ITS heatpump - they are very effective and economical to run if installed correctly, and work whatever the weather unlike the solar collection. Those external hot water pipes should definately be properly insulated - the water in an uninsulated 1/2" copper pipe loses almost 45W/m if the temperature differential inside the pipe to outside is 45C (https://www.engineeringtoolbox.com/copper-pipe-heat-loss-d_19.html)

Thanks for this unfortunately my budget does not allow for a complete new setup at the moment.

21 hours ago, sunset1 said:

We dont have an electric geyser anywhere on the property.

1 hour ago, sunset1 said:

Thanks for this unfortunately my budget does not allow for a complete new setup at the moment.

21 hours ago, sunset1 said:

To help reduce our gas bill was thinking of installation of an ITS FP 2.0m² Vertical Flat Plate Solar Collector or black hdpe piping to preheat the water a bit?

For a flat plate collector or hdpe piping you'd still need a tank of some kind to store the heated water, and it won't help in the early morning before sunrise unless the tank is well-insulated to keep water warm through the night.

If you're using fireplaces for heat anyway, why not look at a Rocket wood-fired water heater (donkey)?

3 hours ago, GreenFields said:

For a flat plate collector or hdpe piping you'd still need a tank of some kind to store the heated water, and it won't help in the early morning before sunrise unless the tank is well-insulated to keep water warm through the night.

If you're using fireplaces for heat anyway, why not look at a Rocket wood-fired water heater (donkey)?

I just figured this out as well that a storage tank is need with a wholebunch of fittings and valves.

I may look into something more passive that does not get too hot.

On 2025/03/18 at 10:18 AM, sunset1 said:

Pipe insulation seems costly at R100 per meter and we would need at least 50m.

maybe not quite as bad... if its 1/2" pipe, this lot may be an option at R 22.77 for 1.8m it sounds more reasonable than you're thinking but not exactly dirt cheap either, but instead of R 5k, around R 640.00 which may be easier to swallow...

Here is an out of the box solution: install a DC geyser element in a bathtub and connect it to solar panels. You would probably have to put an evaporation cover on the tub and there are a few safeties to consider. But I see no reason why you can't have a nice hot bath after a sunny day.

32 minutes ago, frivan said:

Here is an out of the box solution: install a DC geyser element in a bathtub and connect it to solar panels. You would probably have to put an evaporation cover on the tub and there are a few safeties to consider. But I see no reason why you can't have a nice hot bath after a sunny day.

We don't have baths here only showers. Thats not a bad idea for our tub in the forest though:)

On Paloma gas geysers you can set the water output temeperature and it regulates the flame size automatically. I feed mine with water preheated in the electric geyser with whatever PV I have available. The result is that a 19kg gas cylinder lasts us around 120 - 160 days. There is enough PV for me to bypass the gas geyser entirely for about 8 months of the year. I therefore only need to buy one 19kg gas refill per year about.

Edited March 27, 20251 yr by Paulcupine

On 2025/03/27 at 11:58 AM, Paulcupine said:

On Paloma gas geysers you can set the water output temeperature and it regulates the flame size automatically. I feed mine with water preheated in the electric geyser with whatever PV I have available. The result is that a 19kg gas cylinder lasts us around 120 - 160 days. There is enough PV for me to bypass the gas geyser entirely for about 8 months of the year. I therefore only need to buy one 19kg gas refill per year about.

I have been contemplating this method. My first will be insulating the pipes well. Then seeing what the new temp is.

Tell me what does your geyser element draw for preheat? I know they are 3kw. I ask this is we have a smaller system. Be great if it just did 1kw.lets say

2 hours ago, sunset1 said:

I have been contemplating this method. My first will be insulating the pipes well. Then seeing what the new temp is.

Tell me what does your geyser element draw for preheat? I know they are 3kw. I ask this is we have a smaller system. Be great if it just did 1kw.lets say

My 3kw 150l kwikot draws 14a

My geyser had a 4kW element which I downgraded to 2kW. It now runs anywhere from 2 to 5 hours depending on how cold the water is to get fully hot, so interpolate for less PV available. Imho, 1kW is too little. Since I upgraded my solar I'm actually thinking of upgrading it back to 3kW.

This discussion highlights the importance of optimizing both gas and solar systems for efficiency and cost-effectiveness. In Victoria, ensuring the safety and compliance of your gas installations is crucial. Engaging a professional gas safety checks Service can help identify potential issues and ensure your system operates safely and efficiently.

On 2025/03/18 at 10:31 AM, stefan44 said:

Well to preheat the water makes a huge difference in water temp in winter and gas consumption.

I have a 16l gas geyser for 2 bathrooms, It was connected straight inline with the hot water line to the taps, bypassing the electric geyser completely.

with this setup I used 9kg every 9 to 14 days depending on the season. My outside pipes is insulated with much cheaper pipe insulation, I saw the pipes in my roof was insulated with old cloth and rags bound around the pipes with twine, and that also works.

about 6 month ago I put my electric geyser back inline to preheat and feed the gas geyser, I set the geyser thermostat to 40 degrees and changed the element to a 2kw unit.

I use 4kw/h to pre-heat the water (150L) thats fed to the gas geyser, in the dead of winter with only the gas geyser heating the water I could not get the water temperature above 45 degrees.

now with the preheated water the temperature easily reaches 80 degrees in the summer(80 degrees is the geyser's cut out temp) and I have not seen the water temp below 55 degrees and the gas geyser is set to max water flow and min gas, and this have resulted in a 9kg gas bottle lasting 25 days plus....

Whats an electric geyser? never heard of them. I will look them up.

definitely preheating is a good idea along with pipe insulation, passive pays off. Water heating panels is a good idea alright. Water heating panels definitely work very well even way up in the northern hemisphere not great in the winter when days are short and the sun is low.

What about a parabolic mirror with solar tracking focussing energy on a heat-exchanger? or something like these https://www.heliotrack.com/Parabolic.html