Timer for hot water - how effective and cost savings?

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prob

221 posts

Master Geek

#310437 19-Oct-2023 08:51

Thinking of getting a timer so that the hot water cylinder can be used during off peak / free power.

This Bluetooth enabled one looks to be a good buy.

https://www.kiwisparks.co.nz/products/bluetooth-hot-water-cylinder-control-kit

I am looking at a power plan with 3 hours off peak free.

Anyone been this route and what was your experience/
Will three hours be enough to reheat the water (recent cylinder, insulated and family sized but only two of us in the house....)
Anyone tried the Schneider timer (attracted to it becuase we haved Iconic switches with bluetooth throughout the house all ready)

Regards.

PS - just looked at the fine print and the Z energy plan I am looking at says no timed hot water during the off peak / free period.

Really? Any other plans out there that will allow this to happen?

https://www.z.co.nz/products-and-services/power-your-home/ev-at-home-plan/

PPS - Looking at getting solar next year, so would still be handy to move usage to when the sun is out, but I may be confusing a time with a diverter....

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1037 posts

Uber Geek

#3150006 19-Oct-2023 09:04

I had two of these units (not from kiwisparks, but same thing) installed by an electrician about 1 year ago.

One of them still works fine, the other one has failed and will no longer turn on. The electrician is no longer around, and I cannot get Schnieder to respond to emails, so I appear to be stuck with a $150 unit that doesn't work at all.

From a power savings perspective - as long as you schedule showers etc we saw a pretty big difference. For only two people you will 100% be fine. We have a house hold of 6. FYI the power company can't tell if you're scheduling water this way.

Cool concept but now would worried about longevity of the product.

Also - this is anecdotal of course - YMMV.

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tdgeek

29590 posts

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Lifetime subscriber

#3150012 19-Oct-2023 09:22

We have Solar HW, top element is managed by the Solar LCD panel, it has 3 timers. The bottom element is on the grid so we got a timer for that, $200 installed. Reasoning is I keep the grid off all year. Timer is to turn both elements on in my hour of free power. In solar off season I set the top element on for an hour or so in the afternoon

prob

221 posts

Master Geek

#3150036 19-Oct-2023 09:40

OP here.

The electricity company clarified their conditions, no problem using the free power for hot water...

Hi Paul

You can use the free hours/off peak rates for any power consumption except that on a controlled meter which runs at a flat rate 24 hours. For some people this is your hot water.

Check your previous bill to see whether you have separate meters (would be a separate line on your bill)

Rachel

adresdendoll

62 posts

Master Geek

#3150043 19-Oct-2023 09:54

I have two Voltex Bluetooth timers installed (both at the switchboard) - cost about $900 for both, installed (I live pretty rural so Sparky costs are not kind to me). We also have a fair sized grid tied solar setup (8.4 kWh) and use Contact's Good Nights for our two electric hot water cylinders.

Looking at my current usage, I use between 10 and 12 kWh during the "free" period - the vast majority of which comes from the hot water re-heating.

You can work out your potential repayment on investment based on the figures above (if that helps you at all).

tchart

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#3150050 19-Oct-2023 10:06

Works fine if you only shower/bath once a day.

We have a Schneider timer. Works fine but we have a house of 4-5 including 3 teenagers who are home during the day and go to gym etc.

The water does not reheat in time for the evening. I had it turning on/off based on off peak rates for Flick and just never had much luck.

traderstu

328 posts

Ultimate Geek

#3150084 19-Oct-2023 12:04

With only 2 in the house you should be fine.

We have a similar timer to the one you linked to, operating 2 contacters for the top & bottom elements. They both come on at the same time for 1 hr of free power between 5.30 & 6.30 in the morning. We shower late afternoon evening - no problems. Normally only 2 of us in the house but we have had other couples stay with us over several days and still have plenty of hot water. 250l HWC.

BadCo

108 posts

Master Geek

#3150260 19-Oct-2023 19:58

After a month since we moved to flick, we went on holiday. Something I noticed in our usage when we were away, is that sometimes the HWC comes on during peak times. I will be moving HWC to a Shelly 1 PM once it arrives.

On a side note, our cylinder with no usage holds water temp for 13 hours. The HWC is a Therman N180THMB130 installed 2019.

Spyware

3725 posts

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#3150267 19-Oct-2023 20:55

traderstu:

With only 2 in the house you should be fine.

We have a similar timer to the one you linked to, operating 2 contacters for the top & bottom elements. They both come on at the same time for 1 hr of free power between 5.30 & 6.30 in the morning. We shower late afternoon evening - no problems. Normally only 2 of us in the house but we have had other couples stay with us over several days and still have plenty of hot water. 250l HWC.

Recovery time (thermostat = 60, water temp = 15) for a 250 litre tank is 2.43 hours @ 6 kW, so I'm not sure how it stays at temp only heating 1 hr/day.

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RunningMan

8882 posts

Uber Geek

#3150315 19-Oct-2023 21:13

@Spyware because less than 250l/day is being used presumably.

tweake

2296 posts

Uber Geek

#3150317 19-Oct-2023 21:23

Spyware:

traderstu:

With only 2 in the house you should be fine.

We have a similar timer to the one you linked to, operating 2 contacters for the top & bottom elements. They both come on at the same time for 1 hr of free power between 5.30 & 6.30 in the morning. We shower late afternoon evening - no problems. Normally only 2 of us in the house but we have had other couples stay with us over several days and still have plenty of hot water. 250l HWC.

Recovery time (thermostat = 60, water temp = 15) for a 250 litre tank is 2.43 hours @ 6 kW, so I'm not sure how it stays at temp only heating 1 hr/day.

if i remember right, recovery time is basically from a stone cold tank (15c), which is something you don't normally get unless your out of power for a week. if your not using much water, the temp may only drop a small amount, eg down to 55c. plus with some tanks you can go very hot ie 90c. that gives you a lot of storage without dropping below tap temp.

traderstu

328 posts

Ultimate Geek

#3150375 20-Oct-2023 08:40

Spyware:

Recovery time (thermostat = 60, water temp = 15) for a 250 litre tank is 2.43 hours @ 6 kW, so I'm not sure how it stays at temp only heating 1 hr/day.

Yeah, no way do we start at 15 degrees. I'll set the alarm and check it for you at 5.25 tomorrow.

traderstu

328 posts

Ultimate Geek

#3150377 20-Oct-2023 08:52

traderstu:

With only 2 in the house you should be fine.

We have a similar timer to the one you linked to, operating 2 contacters for the top & bottom elements. They both come on at the same time for 1 hr of free power between 5.30 & 6.30 in the morning. We shower late afternoon evening - no problems. Normally only 2 of us in the house but we have had other couples stay with us over several days and still have plenty of hot water. 250l HWC.

To elaborate a little bit on the savings aspect - not much. I used to think I saved quite a bit on EK's hour of power. With the HWC on timer, delayed start on dishwasher, washer, dryer we could typically shift about 35% of our load. Unfortunately, as time goes on with their high daily rate and fairly high peak rate, our power bills are about the same as they were on a bog std Trustpower account when we were renting recently.

We now have an EV and we manage to add about 37km range each morning, which is enough to cover nearly all of our travel. I think this tips it back in our favour again but you can't justify the purchase of an EV for the small savings to be had.

Just in the process of commissioning solar here and will carry on with EK while we evaluate other options.

Kodiack

709 posts

Ultimate Geek

#3160158 16-Nov-2023 14:21

We've had our hot water cylinder on a timer for over a year now. It only runs between 04:00-07:00, and usually heats up in under a couple of hours. I'd wager that the payoff is extremely quick (months, not years). We would've spent maybe $250 all up between timer + sparky friends' labour, though we had it installed while we were also swapping all of our switches and outlets.

It's usually the two of us in the house, and we don't have issues with running out of hot water through the day. One big tip I have is to set your cylinder to a higher temperature. Your hot water cylinder is essentially a big ol' battery; if you're cranking it to 75-80C overnight, you're able to "charge" it really high on the cheapest rates, and you'll have way more capacity than you would at a lower temp because you'll be using a lower mix of your preheated water when e.g. taking showers. Also note that scalding can be a very real danger with higher temps, so change the mix of the water coming from the hot water cylinder if you don't want extremely hot water coming out of your taps at all.

Here's a screenshot of one of the rare days where our hot water cylinder ran for almost the full three hours:

dzh

49 posts

Geek

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#3166436 30-Nov-2023 15:34

I've replaced hot water MCB with ~$20 wireless one from AliExpress. It has decent stats which says we use about $40 worth of power per month. Considering most of it's use is during peak times I'd say it paid itself within 2 weeks.

Haven't really noticed much of a difference in final bills tho.

dzh

49 posts

Geek

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#3166437 30-Nov-2023 15:38

tchart: Works fine if you only shower/bath once a day.

We have a Schneider timer. Works fine but we have a house of 4-5 including 3 teenagers who are home during the day and go to gym etc.

The water does not reheat in time for the evening. I had it turning on/off based on off peak rates for Flick and just never had much luck.

Worth mucking around using homekit - it's pretty good at detecting people home or using humidity sensor + HomeAssistant. Or just crank up cylinder temperature (tho not a fan of scolding hot water when doing dishes).

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