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398 posts

Ultimate Geek

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#2910232 4-May-2022 19:13

One interesting thing about the Electric kiwi move master plan where we are. The solar buyback rate is higher than the off-peak night cost per kWh...

EK MM in Hamilton...

Your electricity rates are:

Peak usage: $0.2527 per kWh

Off-peak shoulder usage: $0.1769 per kWh

Off-peak night usage: $0.1264 per kWh

Solar export: $0.1438 per kWh

Fixed cost of: $2.6400 per day

Nate001

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#2910246 4-May-2022 20:12

eonsim:

One interesting thing about the Electric kiwi move master plan where we are. The solar buyback rate is higher than the off-peak night cost per kWh...

EK MM in Hamilton...

Your electricity rates are:

Peak usage: $0.2527 per kWh Off-peak shoulder usage: $0.1769 per kWh Off-peak night usage: $0.1264 per kWh Solar export: $0.1438 per kWh Fixed cost of: $2.6400 per day

I have no experience with solar, what is a normal rate? I'm guessing not a lot...

As you'll only be exporting solar during shoulder time its really 0.1438 export vs 0.1769 to buy correct?

eonsim

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#2910256 4-May-2022 21:00

Nate001:

I have no experience with solar, what is a normal rate? I'm guessing not a lot...

As you'll only be exporting solar during shoulder time its really 0.1438 export vs 0.1769 to buy correct?

8-9c per kWh is the normal rate there are a few exceptions around 14c (when including GST), while Flickr pays the current spot price so anything from 1-50c depending on the day. The thing about this is during solar peak (11:00-14:00) most solar systems produce an excess that is exported. Which is typically worth maybe a 3rd of what a kWh of power costs at any other time of day. So typically you load shift as much usage as you can into the solar peak. As apart from some smart car chargers and solar diverters most load tends not to exactly match your generation you end up buying a small amount of grid power to make up the difference. So say you generated 10kWh in that time period and use all that plus 1kwh of extra power to make up the difference you end up paying the company 17.7c to run your load.

If instead you timeshift that load to overnight (say a pool pump or car charger) then you have exported 10kWh for $1.438 credit during solar max, you could then buy 11.4kwh off-peak with the 10kWh of credit you exported. So instead of paying 17.7c you now are left with a credit of ~5c for a 22c benefit. Now if you have a larger solar system and export more then you save more and it'll add up over time. Typically if you were with a standard fixed rate company with an 8c the incentive is to load as much on during peak solar to export very little as the 8c export rate vs a 20c per kWh purchase rate strong discourages trying to time-shift power usage over night.

If you can't shift your loads then and instead export the full 10kWh at peak under most companies you'll get 80c credit, which will buy you 3-4kWh of power later when you need it. While for EC if you export the 10kWh you get $1.438 which will buy 11.4kWh over night (probably a good portion of your off peak usage) or 8kWh during the shoulder period.

Nate001

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#2910411 5-May-2022 09:24

eonsim:

8-9c per kWh is the normal rate there are a few exceptions around 14c (when including GST), while Flickr pays the current spot price so anything from 1-50c depending on the day. The thing about this is during solar peak (11:00-14:00) most solar systems produce an excess that is exported. Which is typically worth maybe a 3rd of what a kWh of power costs at any other time of day. So typically you load shift as much usage as you can into the solar peak. As apart from some smart car chargers and solar diverters most load tends not to exactly match your generation you end up buying a small amount of grid power to make up the difference. So say you generated 10kWh in that time period and use all that plus 1kwh of extra power to make up the difference you end up paying the company 17.7c to run your load.

If instead you timeshift that load to overnight (say a pool pump or car charger) then you have exported 10kWh for $1.438 credit during solar max, you could then buy 11.4kwh off-peak with the 10kWh of credit you exported. So instead of paying 17.7c you now are left with a credit of ~5c for a 22c benefit. Now if you have a larger solar system and export more then you save more and it'll add up over time. Typically if you were with a standard fixed rate company with an 8c the incentive is to load as much on during peak solar to export very little as the 8c export rate vs a 20c per kWh purchase rate strong discourages trying to time-shift power usage over night.

If you can't shift your loads then and instead export the full 10kWh at peak under most companies you'll get 80c credit, which will buy you 3-4kWh of power later when you need it. While for EC if you export the 10kWh you get $1.438 which will buy 11.4kWh over night (probably a good portion of your off peak usage) or 8kWh during the shoulder period.

Thanks for the explanation, now I see the significance. That would really change how you use your power in that case.

In a nut shell this must be a form of battery storage, albeit as credit?

Off Peak - (0.1438/0.1264) ~ 113%

Shoulder - (0.1438/0.1769 ~ 81%

Peak - (0.1438/0.2527) ~ 57%

Any idea what real world efficiency of battery solar systems are? Even at lower efficiency there is no cost for a battery so this must be appealing.

eonsim

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#2910440 5-May-2022 10:41

Nate001:

Thanks for the explanation, now I see the significance. That would really change how you use your power in that case.

In a nut shell this must be a form of battery storage, albeit as credit?

Off Peak - (0.1438/0.1264) ~ 113%

Shoulder - (0.1438/0.1769 ~ 81%

Peak - (0.1438/0.2527) ~ 57%

Any idea what real world efficiency of battery solar systems are? Even at lower efficiency there is no cost for a battery so this must be appealing.

It allows you to treat the grid more like a battery, but I doubt they have a battery behind it. I suspect it's just a case of their contracts for purchasing power being set up so that they would rather 'sell their own power' (solar from their customers) than purchase power from the generator companies at their standard rate (or on the spot market if they couldn't obtain contracts for enough power to cover all day time usage). As they pay me $0.1438 per kwh and then sell it to the house down the road for $0.177 per kwh, the 3.3c margin they make may be greater than what they would get as a margin on selling the big gentailers power. Assuming this is deliberate then the lower contract rates they have overnight means they want as much of their customer's usage to occur overnight as possible, and as much solar power they can get during the day to sell to their customers without solar. So the setup strong encourages people with solar to export power during the day to EC, who then on-sell it at a profit. In compensation, they give people with solar some extra power back during the night if they want to use it.

Battery systems are supposed to be in the range of 89-95% efficient depending on the setup. The problem is they can cost as much as $17,000 for 13kwh of storage so unless you need a battery for backup purposes or want to reduce your reliance on the grid as much as possible they're not economically viable.

timmmay

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#2910462 5-May-2022 11:12

eonsim:

One interesting thing about the Electric kiwi move master plan where we are. The solar buyback rate is higher than the off-peak night cost per kWh...

Peak usage: $0.2527 per kWh Off-peak shoulder usage: $0.1769 per kWh Off-peak night usage: $0.1264 per kWh Solar export: $0.1438 per kWh Fixed cost of: $2.6400 per day

If you could sell solar at night you'd be doing great! Given the solar buy-back is higher than the night rate you could hook something up so you just use their off-peak at $0.1264 and push it back into the grid at $0.1438 you'd make 1.5c/kwh!

Jase2985

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#2910535 5-May-2022 12:08

timmmay:

eonsim:

One interesting thing about the Electric kiwi move master plan where we are. The solar buyback rate is higher than the off-peak night cost per kWh...

Peak usage: $0.2527 per kWh Off-peak shoulder usage: $0.1769 per kWh Off-peak night usage: $0.1264 per kWh Solar export: $0.1438 per kWh Fixed cost of: $2.6400 per day

If you could sell solar at night you'd be doing great! Given the solar buy-back is higher than the night rate you could hook something up so you just use their off-peak at $0.1264 and push it back into the grid at $0.1438 you'd make 1.5c/kwh!

unfortunately the devices are not 100% efficient which cuts into the profit and also the cost of said something wont be offset by the profit anytime soon. which makes it not worth it.

timmmay

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#2910665 5-May-2022 20:11

From a very small sample size, going from EK pay ahead to EK MoveMaster the bill for six sequential days has dropped from $66.10 March 25 to 30 (6 days) to $42.08 for April 29th to May 4th (6 days). The March one probably had better weather as well, so less heating. I can't compare the time in between because we had a different number of people in the house. That's a 37% saving! I'll look again in a couple of weeks with a larger sample size. That doesn't take into account the 8% bonus on the old plan - pay $200 get $220 credit.

I've already said what I do, but free hour 5-6am has hot water heating, heating comes on higher (two heat pumps, office fan heater), dish washer, clothes drier if needed. I also turn the heating on at 4pm rather than 5pm taking the heating cycle off-peak. We don't go out of our way too much. I work from home and like my office warm, 24 degrees is pretty comfortable, using a fan heater / oil heater, but that's all daytime / off peak.

tdgeek

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#2910734 6-May-2022 07:10

I just changed yesterday to MM, I'm going to just compare the average per kwH charge to the 32c i was paying before. The rates for EK increase on 13 May so I'll adjust for that as well

All I will change here is set the heated bathroom floors to finish at 7am, and timer pre heat heatpumps prior to 7am to avoid peak morning. Minor saving but why not. I don't use timers on the heatpumps, just use when needed.

Good plan for sure

Leo90

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#2911173 6-May-2022 21:31

Switched to EK on the Movemaster plan a week ago now, average unit price is 14c ex gst. Pretty happy with that..

The daily fee is 20-30c higher than other companies though. I'm in wellington, daily fee is $1.99.

Nate001

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Ultimate Geek

#2911176 6-May-2022 22:00

I see a lot of people talking about average kWh charges on EK's MM. Just a warning that this may not be a good reflection of potential savings. You really need to be taking a weighted average according to your usage habits. The average rate looks attractive because off-peak is 1/3 of the day, but if you're not actively using power during that period its useless.

For example our usage is 51% peak, 31% shoulder, 12% off peak, 5% hour of power. Our weighted average rate is 26.3c/kWh vs average rate of 22.6c/kWh. That is not a huge difference but something to keep in mind and it may effect what is really the best option.

Of course if you use more in shoulder/off peak than peak your weighted average rate will be a lot lower, and could be below the average rate!

Leo90

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#2911177 6-May-2022 22:19

Nate001:
I see a lot of people talking about average kWh charges on EK's MM. Just a warning that this may not be a good reflection of potential savings. You really need to be taking a weighted average according to your usage habits. The average rate looks attractive because off-peak is 1/3 of the day, but if you're not actively using power during that period its useless.

For example our usage is 51% peak, 31% shoulder, 12% off peak, 5% hour of power. Our weighted average rate is 26.3c/kWh vs average rate of 22.6c/kWh. That is not a huge difference but something to keep in mind and it may effect what is really the best option.

Of course if you use more in shoulder/off peak than peak your weighted average rate will be a lot lower, and could be below the average rate!

For what it's worth I calculated my average unit price dividing the price paid by the kWh used after subtracting daily charge. 72% off peak.

eonsim

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#2911197 6-May-2022 23:30

EK MM is so about the time shifting, averaging 80% off-peak and 12% of the total is in the free hour.
Gives an average cost per kWh of 19c when including the supply charges or 13c kWh when excluding supply charges.

k1w1k1d

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#2911236 7-May-2022 07:34

Meridian in Chch on their Super Saver Fixed Rate Plan.

Day: 24.16(27.78incl) 7am-11pm?

Night: 12.47(14.34incl) 11pm -7am?

Daily charge: 30.00(34.50incl)

tdgeek

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#2911238 7-May-2022 07:55

eonsim: EK MM is so about the time shifting, averaging 80% off-peak and 12% of the total is in the free hour.
Gives an average cost per kWh of 19c when including the supply charges or 13c kWh when excluding supply charges.

Yep.There is plenty that can be done in Winter. Timeshift heating to before 7am, avoid peak heating rates, same in late afternoon. Heated floors before 7am. Those on grid hot water can allow it to only heat in off-peak. When we use the dishwasher/laundry 9pm to 10pm, I can shift the free hour to 10pm, to allow overflow to run off peak. Bits and pieces but it all adds up.

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