I mainly write about my journeys with technology regarding APIs, cloud and DevOps. However I’ve also written previously on the topic of efficient energy usage. In 2018, during the drought that hit South Africa, I put in a rainwater harvesting solution at home. Over the last few years, I’ve invested in various initiatives to lower our home energy use, and make our energy use more environment friendly, less wasteful, and obviously to save money. In this post I am going to talk about the different options you have to use gas (specifically LPG) as an alternative to electricity.

Its all about tradeoffs

I think whats exciting about this is that you can approach this with the eyes of a Software Architect - which is about making tradeoffs, in this case about cost vs benefit, as well as considering the human impact the decisions will have on our habits. This is especially relevant for me as as I just finished reading Cloud Strategy - see my review.

Lets look at each option for gas, and consider the following for each:

• Cost to install it: you would need to compare this cost over the years to calculate your pay-back period
• Cost to run it: this mainly is your gas usage each month
• Habits: and probably most importantly, and difficult for us humans, is the habits you will have to change to get benefit from it.

Gas Stove

For the last 10 years or more, we have already been using a 4-plate gas stove/hob, which includes an additional 2-plate electric hob. Even though we have electric plates, we don't use it all. I don't think, from a cooking perspective, if you will notice any difference in moving off an element stove to a gas stove. You will use the same pots and utensils. So there will be no impact in changing your personal habits, except for having to order another gas cylinder when the old one runs out. Or, like what I did recently, I installed a pig-tail with dual gas connectors, so I can connect to 2 gas tanks, and just switch the lever to change between gas tanks. So when a gas tank is finished, I just switch to the next one, and then order a replacement, without impacting our usage at all.
I don't have the costs to install a new gas stove, as ours was done over 10 years ago.

Moving from an electric kettle to a stove-top kettle

About 2 years ago, we stopped using our electric element kettle, and bought a whistling stove-top kettle. This goes directly onto the stove to boil water. Since we already had a gas stove, this provides additional cost saving. But I would argue (but don't have the proof myself) that even if had an electric stove, using a stove-top kettle on the stove would be cheaper than an electric kettle
We bought a 2.5L kettle for R300 from Takealot, but when we bought it 2 years ago from Binuns, it was only R200 for the same model.

From a habit perspective, this will take some adjustments, for two reasons. Firstly, we are used to just flipping the switch on the electric kettle, and now to switch on the stove (gas or electric) seems like additional work. Secondly, an electric kettle is much faster at heating water than a stove-top kettle, so you now need to wait longer.

Now that we are using this on the gas stove, it has increased our gas usage (note the increase in 2020 includes the additional gas usage for the gas geyser). The blue line is the rand cost, and the red line is the accumulated gas size used in kg. The yellow line is the average cost per month.

Control your electric geyser usage

A few years I started with putting in a geyser timer for the electric geyser. We used the GeyserWise device, which gives you a visual screen to see the current geyser temperature, allows you to control and set the temperature, as well as timers to switch off the geyser. It replaces the geysers thermostat with its own, and hooks into your DB board to control power to the geyser when the timers kick in. I set it to limit temperature to 55 degrees, as well as only power on the geyser for 4 hours in the morning, 1 hour at midday, then for 4 hours in the evening.

So now the geyser is only powered on for 10 hours a day, and you can see what the temperature is before going into the shower to avoid a cold surprise.

I will in future include a graph showing my decreased electricity usage over time, as I moved to a gas geyser and stove-top kettle.

Electric geysers are wasteful

If we look at electric geysers from a Software Architects perspective, we can see its a very wasteful device. It stores water, and pre-heats it, even before you use it. Because it does not know when you going to need the water, it basically keeps the water constantly hot. Essentially this is like keeping your kettle perpetually boiling for 24 hours a day, just so you can have hot water for your 3 cups of coffee throughout the day, i.e. not very smart. So while it is convenient, ensuring you always have hot water, it’s expensive and very wasteful.

Gas geysers

Gas water geysers on the other hand, provide Just In Time heating. It does not store the hot water to pre-heat it; rather it instantly heats up the water as it passes through the gas appliance. It has flames, powered by gas, that heats up the pipes as the water passes through it. So when you open your tap, the geyser will light up the flames, heating the water as it passes through. Its very economical, for 2 reasons:

• you aren’t wasting energy by constantly heating up the water
• from a cost perspective, it will cost you less to run and operate a gas geyser, based on the gas that you use, than paying for electricity

Probably the most important benefit is that with gas geysers, you only need to set it to the desired temperature, and not higher. Electric geysers in South Africa are usually set to 65 degrees celsius, for various reasons: higher than 60 degrees kills off bacteria, dishwasher machines that don't heat water themselves will need pre-heated water, and maybe a few others. But anything higher that 50 degrees is likely to scald you, so therefore we normally mix in cold water as well to bring it to the desired temperature, which is probably between 43 and 47 degrees (this article claims the magic number is 112 Fahrenheit or 44 celsius), although women prefer it hotter. How wasteful: you heat up the water to 65 degree, but need to mix in cold water to make it actually usable?

But the main reason why practically you need to set it to some temperature above your desired temperate is because electric gas geysers store water, so once it reaches the setting of 65 degrees, and you open the tap, cold water flows in to the geyser, which will lower the overall temperature. And electric geysers store a lot of water, so it will take some time to heat up the new cold water. So if you in a shower for 10 minutes, when you are finished, overall the temperature of your electric geyser has decreased, because you used up the hot water, and it is still heating up the new cold water. I practically seen how quickly this works when I started using the GeyserWise device to control the electric geyser. I set it to maximum 55 degrees, so when I started my shower it was 55 degrees, but ten minutes later when I came out of the shower it was at about 37 degrees, which explained why the last few minutes were not that enjoyable. But with a gas geyser, it can maintain the desired temperate at all times, as it does not store water, so you can never finish up the hot water, as its always instantly heating up the water to the desired temperate. So with a gas geyser you can set the maximum temperate to 47 degrees (or whatever you choose), and never have to mix in cold water, and still maintain that temperature over the duration of your shower. Read that again: you don't need to mix in cold water, and can simply just open the hot water tap, and the water is already set to the perfect temperature. Therefore, with a gas geyser, you can set it to the desired temperate, and not higher, saving you heating costs.

In my opinion, using a gas geyser requires a fairly large habit change, mainly because it's not as stable as an electric geyser. It can turn cold because was water pressure changed for some reason, or the gas tank was finished (or almost finished, which results in less gas pressure to power up the gas geyser). The battery used to ignite it can wear down and will need replacement. Sometimes wind and rain can affect it, resulting in it not working or not heating up the water hot enough while its raining or very windy. In addition, because you don't need to mix in cold water, this adds to the adjustment thats us humans need to make.

Types of gas geysers

After reading this brilliant article to understand the types and benefits of gas geysers, and this one, we can see there are two types of gas geysers:

1. Standard - Pressure-based: cheaper, but needs constant pressure to maintain the flame. Mixers or energy-saving shower heads can affect them.
2. Advanced - Flow/Temperature-based: more expensive, but any water pressure works.

Most types need an electric source to ignite the flame. Some use a D type battery, while others need a direct connection to the power grid (i.e. Eskom, CoJ) , which means the geyser wont work during load-shedding or other causes of power-grid outages. A backup battery/UPS can be used to power up the ignition during power failures, but this adds additional costs.

There are also multiple types of ways to install it. It could be standalone, or in series with other geysers (gas or electric). A friend of mine has the water mains flowing into a gas geyser, which flows into an electric geyser. You could do the other way as well: mains to electric, then into a gas geyser. I have an electric geyser and a geyser side by side, and using a valve, can change which geyser I want to use. So I normally use the gas geyser only, but if there is a problem, I kept my old/existing electric geyser, and by changing the direction of the valve, mains water flows into the electric geyser only, bypassing the gas geyser. The plumber who installed mine had a solar geyser flowing into a gas geyser. So during the day, the solar geyser heats the water up to 45 (or whatever you need), and when it flows into the gas geyser, the flame does not even need to light up, because the temperate is already at the desired temperature. Only at nights or on cloud days, when the solar geyser cant heat up the water enough (perhaps maybe at 35 degrees), then the gas geyser lights up, to top up the heat just enough as required. So you run almost on free hot water during the day, and need minimal gas to raise it up to desired temperate at night.

Over the years, I have used both types of geysers:

Pressure-based

In 2016, I installed a Totai 9 liter gas geyser, to power a single bathroom (shower and basin). This is a standard gas geyser, which means its pressure based. It costed R2200 excluding fitment and pipe, etc. It used a simple D type battery, and had 3 dials that you needed to adjust the temperate. It was confusing, and had a dial for winter and summer, and we realised that you needed to adjust all 3 dials as the seasons change in order to maintain your desired temperature. We had various issues with pressure and back flow from the mixer taps that caused the flame to switch off during usage. Our problem was that we thought it was just like an electric geyser, so we used to try to adjust the temperature of the water by using the tap and mixing in cold water (as we normally did with an electric geyser), which caused back-flow and turned off the gas geyser. Showers turned cold in the middle, and you needed to switch off the tap, and then start again. Only after a few years we realised we should set the gas geyser temperate to the desired temperate setting, which wont require us to mix in cold water with the tap. In hindsight, it's not a bad geyser, once you understand how to use it (and that it's not an electric geyser). I wouldn’t refer it, especially after using the Atlas flow-based one below.

Flow-based

During lockdown in 2020, our main electric geyser serving the rest of the house stopped working. I therefore replaced it with an Atlas 16L flow-based gas geyser. Again using a D-type battery, this one had a simple button to set the desired temperate in degrees (unlike the Totai which had multiple dials) and an LCD screen to see the actual temperature. The total cost including geyser, installation and piping (for water and gas) was R10 000.

In this setup, I have gas tanks that feed both the gas water geyser and the gas stove. Two gas tanks, controlled by pig-tails valves, allow to switch from one gas tank to another when the one is finished. So with both the gas stove and gas geyser, I used up a 19kg gas tank in 6 weeks.

Gas Heaters

Instead of bar heaters, we also use gas heaters in winter. Under heavy usage, on very cold days, you could use up a 9kg gas tank in ten days. But normal usage on most winter days wont need that much gas.

Antracite coal heater

Technically not gas, but having an anthracite coal stove (or even a wood heater) is an amazing source of heat in winter. It warms up the lounge and surrounding rooms, and we even place the stove-top kettle on top, which provides us with (free) hot water for coffee through out the day.

My coal costs over the years is as shown in the diagram:

What was unique this year was the amount of coal used of 1500 kg, vs 1000kg and 750 the previous two years. This is probably due to the very cold winter we had, which caused us to burn the fire hotter and longer. The average cost per kg was higher this year, because I did not order in bulk, and this had higher costs, and delivery costs per delivery.

My total costs during winter

In July this year (2020), my electricity bill was just R1000 for our family of four. The other costs to add were the average monthly gas costs of R211 and average monthly coal cost of R616, which took my average monthly total energy costs to R1827.

My neighbour, also with a family of four, and a similar size house, paid R4000 for electricity that same month. His increased costs can be attributed to an electric geyser, electric kettle and element/bar heaters. So we can see that the cost savings of switching to gas are very real.