Making the most of night rate power

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Shoes2468

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#143207 6-Apr-2014 21:37

Hi everyone,
With the impending winter months upon us I was after ideas for ways to reduce daily power consumption and instead maximise the night rate which is less than half the price. The obvious ones are running appliances like dishwashers and washing machines at night but for us this is not an option due to the noise of these machines when trying to sleep. We currently run two heatpumps during the winter months, one to heat lounge kitchen and one to heat the hall way/bedrooms. One major dilema I have is wether to leave the lounge heat pump over night or should I turn it on at 6:30am when waking, the problem with that is it uses the day rate to heat from scratch, I could program it to start earlier when the night rate is on but it seems a bit hit and miss to when the night rate is actually on, genesis energy say night rate is on for 7.5 hours between the hours of 9pm and 7am. Anyone have any other suggestions how I could better manage this or anyother suggestions about using less day rate

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#1019639 6-Apr-2014 22:57

I wish we had night rate power.

AFAIK we don't - it's provision seems very variable in NZ and up to the power company whether it happens with some quaint thing called a 'ripple switch', whereas in the UK it was fairly much universal - power after midnight was always cheaper.

SaltyNZ

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2degrees

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#1019644 6-Apr-2014 23:18

We don't have it here either, so I'm thinking of switching to solar at night.

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Aredwood

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#1019645 6-Apr-2014 23:41

SaltyNZ: We don't have it here either, so I'm thinking of switching to solar at night.

How do you use solar power at night? Am I missing something - Night time means no sunlight so how could you possibly use solar power at night?

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#1019646 6-Apr-2014 23:44

We had night rate before. We moved to Powershop for better overall saving. I don't see the point of limited night rate when you tend to do most things when you're awake ;-)

To answer your question, set the heatpump to start before you wake up - don't leave it overnight. There is no such thing as 'cold' start for a new heatpump.

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#1019648 6-Apr-2014 23:53

To the OP

How is your hot water cylinder controlled? Does it only heat at night or is power available to it all the time? And does it have 2 elements or just the 1? If all the time switch it to night rate only. You can also get a "one shot" circuit connected to the cylinder as well. if you run out of hot water and can't wait till night time press the button to have it do just 1 heating cycle. If you have a chest freezer, stick it on a timer so it will only run during the night rate period. Swimming pool or spa, only run pump during night rate period.

nigelj

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#1019649 7-Apr-2014 00:21

Shoes2468: Hi everyone,
With the impending winter months upon us I was after ideas for ways to reduce daily power consumption and instead maximise the night rate which is less than half the price. The obvious ones are running appliances like dishwashers and washing machines at night but for us this is not an option due to the noise of these machines when trying to sleep. We currently run two heatpumps during the winter months, one to heat lounge kitchen and one to heat the hall way/bedrooms. One major dilema I have is wether to leave the lounge heat pump over night or should I turn it on at 6:30am when waking, the problem with that is it uses the day rate to heat from scratch, I could program it to start earlier when the night rate is on but it seems a bit hit and miss to when the night rate is actually on, genesis energy say night rate is on for 7.5 hours between the hours of 9pm and 7am. Anyone have any other suggestions how I could better manage this or anyother suggestions about using less day rate

On the old United Networks network (now officially called 'Vector North') night rate was 11pm to 7am (8 hours), but the plan was discontinued April last year as they wanted to do more fine grained time of day charging via smart meters, (but oddly now appears to be back according to 3 of the big 4 power retailers - going to verify tomorrow and still no sign of the smart meter ToD charging).

One big thing, if you have a hot water cylinder of sufficient capacity and insulation, you might want to get an actual timer put on to the element (well replace the safety switch with switch & timer) so it only runs during night (the Waitemata Electricity Board back in the day at one point used to do this for free (with a day-night meter conversion & ripple control ('eco meter') too) when capacity was really low, and usage was high-ish). A sparkie can do this for you (but apparently the modern timers aren't overly cheap).

Can't really talk about heatpumps due to a lack of one.

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kiwitrc

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#1019685 7-Apr-2014 05:53

Geektastic: I wish we had night rate power.

AFAIK we don't - it's provision seems very variable in NZ and up to the power company whether it happens with some quaint thing called a 'ripple switch', whereas in the UK it was fairly much universal - power after midnight was always cheaper.

Pretty sure you can get Day/Night using Genesis in the Wairarapa, this doesnt mean ripple switching as such but looks like they can offer that as well.

kiwitrc

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#1019687 7-Apr-2014 06:05

Aredwood:
SaltyNZ: We don't have it here either, so I'm thinking of switching to solar at night.

How do you use solar power at night? Am I missing something - Night time means no sunlight so how could you possibly use solar power at night?

You need to use "internet enabled solar", when its dark here you get your solar from enabled ones in parts of the world where the sun is still shining.

Jaxson

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#1019708 7-Apr-2014 07:01

kiwitrc:
Aredwood:
SaltyNZ: We don't have it here either, so I'm thinking of switching to solar at night.

How do you use solar power at night? Am I missing something - Night time means no sunlight so how could you possibly use solar power at night?

You need to use "internet enabled solar", when its dark here you get your solar from enabled ones in parts of the world where the sun is still shining.

lol to that one.

To answer the question though, the solar cells charge batteries, and then you use their stored energy at night.

Recently there has been a lot of interest in direct online solar to top up your mains supply during the day. For many families though there is no one home during the day, and the peak loads are in the morning for hot water and in the evening for cooking, at which point there's not a lot of sun around...

With regards to night rates, it all about deferring load until that period, so putting the washing machine (hopefully a quiet one) and a dishwasher on delayed starts, so they begin during the cheaper period. Night store heaters did this, by heating bricks slowly during the night, so they'd release their heat into the following day without using power then. It's rare for domestic users to actually have a night rate these days unfortunately.

pctek

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#1019709 7-Apr-2014 07:09

We currently run two heatpumps , one to heat lounge kitchen and one to heat the hall way/bedrooms.

2?!!

Why not get rid of one and run a heat ducting system to the hall instead.

timmmay

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#1019713 7-Apr-2014 07:41

Moving heat from a heat pump from one end of a house to another doesn't work. If you suck 20 degree air out of the room and pump it into another room I'm told it drops 2-3 degrees on the way. You could put massive insulation onto the ducting, but you'd need a large volume of air moved because it's only 20 degrees, and it'd strain your heat pump. It works fine when you have a fireplace, as the air above it is more like 60-80 degrees. IMHO, and I asked a lot of people about it, it's not practical. I also have two heat pumps, one at each end of the house.

OP: you've gotten some good ideas, but it sounds to me like it's not practical for you to make much use of night rate power. A night store heater that heats up concrete blocks might work, but it's still less efficient than a heat pump on daytime rates. A timer to put hot water onto night rate power is probably the most practical suggestion, since hot water uses around 1/3 of your power. Try to turn your heat pump on at 5am or something to heat the house up, though if there's a drop of more than say 3 degrees between when you turn it off at say 10pm and 5am you need to look at your insulation. I have a well insulated but very old house, if it's 20 degrees at 10pm it's usually 17-18 degrees at 6am. I leave the heat on only on the coldest nights.

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Jaxson

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#1019716 7-Apr-2014 08:02

timmmay: Moving heat from a heat pump from one end of a house to another doesn't work. If you suck 20 degree air out of the room and pump it into another room I'm told it drops 2-3 degrees on the way. You could put massive insulation onto the ducting, but you'd need a large volume of air moved because it's only 20 degrees, and it'd strain your heat pump. It works fine when you have a fireplace, as the air above it is more like 60-80 degrees. IMHO, and I asked a lot of people about it, it's not practical.

Spot on. You need a heap of excess heat to make this type of system work.

You're taking warm air and passing it out into the uninsulated roof space and back into your house. The R values are 0.5 from memory, which is practically nothing. If you wanted 20 degrees in your end bedroom you'd actually be cooling it with this approach. Log burners are often marketed as being suitable for an x bedroom house, with no explanation given as to how that heat is supposed to travel around said house. This circumstance is ideal for heat transfer, but a heat pump is not. A heat pump is an efficient fan heater, nothing more (other than the ability to cool also).

Remember a hot water cylinder must exceed 60°C for more than one hour a day to prevent Legionnaires disease.

edit: just came back to add this pretty handy link ...

Geektastic

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#1019760 7-Apr-2014 09:48

kiwitrc:
Geektastic: I wish we had night rate power.

AFAIK we don't - it's provision seems very variable in NZ and up to the power company whether it happens with some quaint thing called a 'ripple switch', whereas in the UK it was fairly much universal - power after midnight was always cheaper.

Pretty sure you can get Day/Night using Genesis in the Wairarapa, this doesnt mean ripple switching as such but looks like they can offer that as well.

We're on Meridian and all the comparison websites tell me that for our sizeable $5000 a year bill it is still the cheapest.

kiwitrc

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#1019784 7-Apr-2014 09:59

Geektastic:
kiwitrc:
Geektastic: I wish we had night rate power.

AFAIK we don't - it's provision seems very variable in NZ and up to the power company whether it happens with some quaint thing called a 'ripple switch', whereas in the UK it was fairly much universal - power after midnight was always cheaper.

Pretty sure you can get Day/Night using Genesis in the Wairarapa, this doesnt mean ripple switching as such but looks like they can offer that as well.

We're on Meridian and all the comparison websites tell me that for our sizeable $5000 a year bill it is still the cheapest.

That is sizable. What the comparison websites cant do is give an indication of what you would pay if you only heated your hot water (assuming electric) on night rate. I have a timer on my switch board that turns the hot water on during the night rate only. HW is usually the single biggest contributor to the electric bill, but obviously there are savings in delaying the dishwasher, washing machine, underfloor heating and anything else you don't need to run during peak power periods.

maslink

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#1019791 7-Apr-2014 10:16

Shoes2468: Hi everyone,
With the impending winter months upon us I was after ideas for ways to reduce daily power consumption and instead maximise the night rate which is less than half the price. The obvious ones are running appliances like dishwashers and washing machines at night but for us this is not an option due to the noise of these machines when trying to sleep. We currently run two heatpumps during the winter months, one to heat lounge kitchen and one to heat the hall way/bedrooms. One major dilema I have is wether to leave the lounge heat pump over night or should I turn it on at 6:30am when waking, the problem with that is it uses the day rate to heat from scratch, I could program it to start earlier when the night rate is on but it seems a bit hit and miss to when the night rate is actually on, genesis energy say night rate is on for 7.5 hours between the hours of 9pm and 7am. Anyone have any other suggestions how I could better manage this or anyother suggestions about using less day rate

Yes, if there is a significant drop in temperature overnight, then doing the initial heating on night rate will potentially save you some money. If, for example, you needed to run a 6kW Heatpump for 1hr/day to return the room to the desired temperature, then this would be a saving of ~2kWh @ 10c/kWh (rate differential), or $6/month. There are probably bigger savings from Hot water load and other timeshiftimg however.

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