Time to give electricity the flick?

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#1481130 29-Jan-2016 11:37

fortydayweekend:

A small battery (10kWh) might even make sense soon - if you're still using 10kWh of power in the winter evenings, you could avoid 10 * $0.12 = $1.20 of lines charges each day by charging the battery at the offpeak rate and using it during the peaks.

Maybe. I just looked at a random winters evening, we used 13kwh of power at around 13c/kwh, though some was lower at 10c/kwh. Overnight rates were 8c/kwh. Battery and inverter technology will probably have to get a lot cheaper before that narrow margin makes sense. Install costs could be expensive too It may make more sense when power prices are higher, later summer when the lakes are dry.

Heat pump driven night store may make sense, but that takes a lot of thermal mass to be worthwhile.

fortydayweekend

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#1481134 29-Jan-2016 11:45

timmmay:

fortydayweekend:

A small battery (10kWh) might even make sense soon - if you're still using 10kWh of power in the winter evenings, you could avoid 10 * $0.12 = $1.20 of lines charges each day by charging the battery at the offpeak rate and using it during the peaks.

Maybe. I just looked at a random winters evening, we used 13kwh of power at around 13c/kwh, though some was lower at 10c/kwh. Overnight rates were 8c/kwh. Battery and inverter technology will probably have to get a lot cheaper before that narrow margin makes sense. Install costs could be expensive too It may make more sense when power prices are higher, later summer when the lakes are dry.

Heat pump driven night store may make sense, but that takes a lot of thermal mass to be worthwhile.

Interesting, the Wellington lines co just gives a discount rate for 11pm - 7am power, which Flick is passing on to you. The differential isn't nearly as much as in Auckland - between 3c-9c. It'd take a lot more to make a battery worthwhile then.

You could also pump water into a rooftop tank at night and run it through a micro-hydro turbine during the day :)

slip

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#1481227 29-Jan-2016 13:55

fortydayweekend:

timmmay:

fortydayweekend:

A small battery (10kWh) might even make sense soon - if you're still using 10kWh of power in the winter evenings, you could avoid 10 * $0.12 = $1.20 of lines charges each day by charging the battery at the offpeak rate and using it during the peaks.

Maybe. I just looked at a random winters evening, we used 13kwh of power at around 13c/kwh, though some was lower at 10c/kwh. Overnight rates were 8c/kwh. Battery and inverter technology will probably have to get a lot cheaper before that narrow margin makes sense. Install costs could be expensive too It may make more sense when power prices are higher, later summer when the lakes are dry.

Heat pump driven night store may make sense, but that takes a lot of thermal mass to be worthwhile.

Interesting, the Wellington lines co just gives a discount rate for 11pm - 7am power, which Flick is passing on to you. The differential isn't nearly as much as in Auckland - between 3c-9c. It'd take a lot more to make a battery worthwhile then.

You could also pump water into a rooftop tank at night and run it through a micro-hydro turbine during the day :)

Interestingly I looked at some of these options. Batteries are too expensive for my requirement but I thought the pump / turbine may be possible until I calculated I would need an Olympic sized swimming pool 3 meters off the ground of my property.

This is an interesting article on the different options although his requirements where much larger.

http://physics.ucsd.edu/do-the-math/2011/09/got-storage-how-hard-can-it-be/

timmmay

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#1486437 6-Feb-2016 12:35

I've done some calculations this morning to work out how much I'd save if I had water heating only between 2 and 4am. This meets the requirements to heat to some given temperature at least weekly to prevent legionaries disease.

I've based it around these assumptions, with a couple of notes:

80% of the power used in the 60 minutes that we get up is hot water. This seems reasonable as we have efficient lighting and don't use much heating at that time - if we heat in the winter it's before we get up. Towel rail runs after this period, but underfloor heating is running.
I can't estimate evening hot water usage, so I use the morning usage, but I take 95% instead of 80%. This is because we wash the large dishes by hand every evening.
We're two adults, and we shower 6am - 6:30am in the morning, and randomly in the evening. There's also an occasional bath which I haven't taken into account.
I haven't taken into account the random bits of heating to keep the cylinder warm during the day. This probably adds to the savings.

The data came from:

Flick sent me my usage for 5 months May to September a while back, when I asked them to
Geoff from Nodewatch sent me my node's usage over a period of years. You can download pricing history by month here, but he'd already done it for my node so I used his data (I checked a few points and it as accurate).
I wrote a couple of little Java programs to parse the long form data. Excel could probably have done it, but the formula would've been a PITA to write.

My working is available on Google Drive:

This document works out how much money I think we'd save based on our actual usage from Flick, May to Sept 2015. This suggests savings of $139/year, though I note that I have no data for summer, and I think prices are highest at the end of summer.
This document estimates how much we'd save over the 2009 - 2015 period, based on estimated power usage. This comes out at $175 to $210 per year.

I've recently gotten an estimate to fit a timer, a heavy duty relay, and labor to fit a timer, around $400 inc GST. This suggests a payback period of around two years.

gchiu

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#1486679 6-Feb-2016 21:46

The cost for me was $378 for a EZYswitch (SMS controller), $34+gst for a 12VDC relay on my switchboard, and 30 mins of electrician labour ( he was here doing other stuff ). I already had a spare sim card.

Phone is programmed to send a text at 5 am to turn hot water on for 2 hours. And if it's cold during the day, I can send a text to turn water on for an hour if I want a hot shower in the evening.

It was useful initially for it to sms me back with acknowledgements but since it all works I let the sim card balance expire so it can't send me texts, but it can still receive my commands.

But I also gain another port on the EZYSwitch to control another device or monitor something else.

I should do the analysis to see what my payback period is as well. But it's a little tricky since although I might turn the power to the cylinder on for 2 hours, it may only need 1 hour until it switches off due to the internal thermal regulator.

richms

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#1486699 6-Feb-2016 23:05

Ouch. I was just going to get a contactor put on it with a plug to put into a wemo.

Richard rich.ms

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#1486728 7-Feb-2016 00:18

richms:
Ouch. I was just going to get a contactor put on it with a plug to put into a wemo.

If you get a Wemo from the UK it's rated at over 3kw too. Then with Nodewatch and IFTTT you can control it based on the current spot price. Once it goes below a certain spot price let it turn on, and then when it's goes above a higher spot price you can get it to turn off automatically.

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#1486730 7-Feb-2016 00:32

I wouldn't trust the silly little relays they put in the things with constantly switching 13 amps in any case.

Mine will be timed so that it runs when the sun is out, because I am not going to bother with a complete solar diverter system just yet as there is going to be very little spare power during the day.

Richard rich.ms

timmmay

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#1486746 7-Feb-2016 07:13

Text control sounds like a pain in the butt to me. I'll put in a regular timer. I'll not even put in a bypass switch, but I'll do that when we redo the switchboard whenever that is. We still have fuse wire for a couple of circuits...

TonyS071

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#1486938 7-Feb-2016 13:12

Brand new to Geekzone, and a recent Flick convert, haven't even got the first bill yet. I installed a hot water timer switch a week ago, and it's working out well according to the Flick web portal graphs.

My question is regarding Nodewatch however - is there a reference somewhere to correlate street address to the relevant node code? (Porirua/Titahi Bay in case anyone knows it off the top of their head).

fortydayweekend

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#1486947 7-Feb-2016 13:21

TKR0331 for Titahi Bay I think

timmmay

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#1486958 7-Feb-2016 13:55

That's the node I have in Johnsonville, so even if it's not perfect it'll be pretty close. No idea how to look them up.

Tony, what's your % saving compared with your old company, according to Flick? It might not tell you yet. We're at 18% this period and 22% overall, with minimal behaviour modifications - we run washing and drying off peak if we can, and the dishwasher runs at 3am. In winter we put the heating on earlier than we otherwise would, to avoid the evening peak, but there's not much you can do about needing heating during the evening in winter.

TonyS071

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#1486973 7-Feb-2016 14:14

Thanks for that - big help. I don't think flick will tell me, as I came from Powershop so it's a bit hard for them given the variability. I recall the signup blurb saying something about comparing to the majority retailer instead. My trade me sourced hot water timer cost me $25 including installation (which luckily was free). That and using the dishwasher delay button is the sum total of my changes so far.

As a matter of interest, where have you set the Nodewatch threshold, and can you change easily it if it starts to spam you? Nodewatch didn't ask me to login when I peeked into the site today. What frequency emails does that generate? I guess I only want to know if the price goes OTT.

timmmay

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#1486984 7-Feb-2016 14:38

Electrician quoted me $400 for a hot water timer, details here. Summary: even $100 timers will burn out because of the high regular load, care is required.

Yes you can change Nodewatch thresholds easily. My threshold is 14c/kwh (plus some at higher numbers), I think I've gotten a half dozen emails in the past 3-4 months. In winter they're a lot more regular, as power prices vary a lot more. 14c/kwh plus line charges and GST is about what most people pay all the time in Wellington.

TonyS071

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#1486999 7-Feb-2016 15:01

I guess time will tell about how long it lasts. Rated for 25amps so it has a bit of headroom. I was surprised it actually had a real contact, I was expecting a SSR actually.
Scope to fine tune its running period yet, although the price at night appears quite consistent between 12 and just after 6 looking at the graphs. Early days, but I suspect it only needs a couple of hours or less running in normal circumstances. I have it set to on between 0030 and 0600 at the moment.

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