I am renting a house for two years only. It has four geysers.
My prepaid bill electricity for this month was R5500.
The owners of this house in Northcliff seems not to have noticed the loadshedding and disastrous increase in energy prices of the past 5 years. Also, no cognisance of the upcoming increases.
It has no geyser times, no solar geysers, no solar system, three phase supply with a prepaid meter.
Also, no borehole. Swimming pool and fish pond with associated two motors - but they are on timers.
I have not inspected the geysers, but I suspect some of them have 2kw and some have 4kw elements. Is there a cheap way of getting them on timers?
I had Geyserwize timers at my old house, but they all failed in 3-4 years. And they are not cheap.
What options do I have for switching on the geysers on a fixed schedule, 1 hour each per day?
What is cheap sir. R300-400 range or R500-570 range.
There is really nice electronic timers available from most electrical wholesalers at under R400 and the CBI asutes from builders for about 550 and then the CBI electronic timers for Roughly R700. CBI astude allows for monitoring and changes made over your wifi network, while the others needs someone to change the settings manually.
And if there is no space in the DB, use these CBI geyser isolators, allows you to set up a timer as well. Easy install, just replace the Geyser Isolator with below and link to the wifi.
I’ll add my usual bit here about how Geyser timers doesn’t really save (much) money. The only way they save money is if you time it such that the last guy gets out of the shower 3 minutes early because the water is getting cold. Then it works, because it actually reduces the water consumption Make sure the wife is not the last person in the shower.
The reason is simply that the maximum you can save on hot water, if you ignore the consumption totally (or assume that is constant), is 2kWh per day per geyser. That is the standing loss on the average 150 liter geyser.
The rate at which a geyser cools down, is proportional to the difference between the water temperature and ambient, which means the cooler it gets, the slower it loses energy while just sitting. The idea with a timer, is to let the geyser sit at a lower temperature while it is not used, thereby reducing standing losses.
Therefore, the maximum a geyser timer can ever save, is 2kWh per day (per geyser), and only if you time it precisely so that it turns on just before you need it, and switches off soon enough so that the tank is essentially cold after the last guy showered.
Where timers shine, is backup for solar geysers. Then you don’t want to heat the water until at least 3PM-ish, to give the sun priority.
The formula for a geyser cooling down is T = ce^kt, where T is temperature, t is time, and c and k are constants you determine by plugging in known values. c will be the starting temperature (55°C), because at time t=0, T = c. k you have to calculate by plugging in the standing loss and t = 24 hours.
I think many people underestimate how much electricity a pump running 6/8/10 hours a day consume - unless running at an absolute minimum already there might be more savings there than with the geysers. I think some of the MajorTech type timers have a 3kW limit, so if there are 4kW elements that could also be problem.
Another nice thing with a decent, not just a dumb timer switch, or for me anyway where I believe you can also save a bit more, is better, more precise temperature control.
Now in summer my Geyserwise is set to only 45 degrees and I should actually lower it a bit more because I’m still adding cold water to my shower. Plus of course then I adjust my timer settings as well for only the time it takes to get ambient water to 45 degrees, plus 5 minutes for luck.
I use timers to heat the geyser during sun hours, also have turned up my thermostat to max 65 degrees, so essentially storing hot water ( granted temps drop by 12 degrees overnight) There is just me and the long haired one, so no danger of small children scalding themselves at 65 degrees.
Sometimes a house have multiple geysers and only one or two people using one. You dont need to heat the full 150 or 200 liters. Hot water goes to the top of the geyser and get used first. I have seen on multiple occasions that heating a geyser for 30-45 min per day gives enough hot water for the requirements of the occupants. If you dont need 150l of hot water there is no need to heat it, If you only want to heat what you need, a timer works great and does save money, even if the Geyser in not connected to a solar system.
I think one can save more than 2kwh per day by using a timer.
The key remains discipline though.
I live alone, during summer a gas geyser will actually be ideal for me, or a 50l geyser heated to 40 degrees will also be fine, I shower in less than 10 minutes.
During winter if I don’t focus, I can very easily stay under the shower till I feel the water start getting cold, with my 150l geyser :smily
Agree, I did the maths and tracked in Home Assistant. Really not much point in adding a timer if the geyser is decently insulated. You are just offsetting the heating time and allowing more opportunities for things like Legionnaires disease.
I have a combination geyser (Tubes for PV and 2kw element).
I don’t want to keep the water hot all the time using electricity.
Warm the water for 60 min from 04:30 for morning showers and then top up (if needed) between 14:00 and 15:30. PV mostly does this so no electricity used.
I heat 1 x 150 (Shelly NodeREd control) and 1 x 100 (Geyserwise Tuya) only by using solar.
Obviously if people want to shower, and it is weather days, then Eskom.
150 vertical heats until the element switches off, or the timer runs out. Give it 2 hours per day.
100l is heated to whatever the season dictates. Summer it is very hot.
That’s essentially the same thing I was after. And the tank has to be COLD after you’re done. The geyser has to be switched off BEFORE you even start showering, in this scenario.
The time period, of 30 to 45 minutes, is also bang on what I would expect. From an hour upwards, you are probably heating too much water. The entire tank can be heated from cold in about 2.5 hours. Recovering the standing loss of one day takes about 40 minutes.
Then I agree, you can save more than 2kWh per day, but now you are saving it by heating less water, ie on the consumption side rather than taking advantage of newton’s law of cooling, and a lower average temperature.
This is a good point though. It’s an additional important question to ask before recommending (or dismissing) a solution.
Reading that, it dawned on me. Bad weather days, heat geysers to like 40deg, will be cold if you take too long.
Also to ponder on: The shower head AND how big is the tap open?
Wife, daughter, full blast piping hot water (I burn under it) costs a lot of hot water, and water can run cold being 100l geyser.
Me, just enough water to be comfortable and can shower for much longer if I want with no cold water.
All about 1) the shower head and 2) how big one opens the taps.
Cause, wide open blasting hot taps, Effect, more heating moola.
Oh yes. As a boarding house kid… that is what you did in winter. Preserve the hot water so you can shower longer.
Side story incoming.
I can tell you a great deal about what we had to do to get hot water in the boarding house. The “geysers” actually used Diesel. When the thermostat said it was time to come on, it would start up a big air blower, and then a second later it would spray the diesel and ignite it. All automatically. But it had a safety feature that would lock out the system if the Diesel didn’t ignite, and this happened more often than you know. The boiler room was locked, of course, but we had long ago discovered that a certain wooden panel, removed in the bathroom, gave you access to a crawl space that could be followed into the boiler room. So we would crawl down there, and hit the restart button.
Soon enough, the powers that be noticed the dusty footprints leading from the crawl space to the geyser. They proceeded to block up the crawl space. They never fixed the boilers.
By then, things were so bad in Namibian schools, that we didn’t have any Diesel anyway, so most showers were cold. The government had simply neglected to pay the bill.
And then, soon after that, we had no running water in the boarding house at all. We would take our towels and soap, walk down to the fire hydrant in what was known as the “grass square”, a small shielded area at school, and we’d take a bath there, usually around midnight when nobody was around.
Then, I finished school, and it was someone else’s problem after that.
Make sure the wife is not the last person in the shower.