Solar update - 3 years in

How are our power bills?

Negative bills for Jan, Feb, Mar 2025

We changed from Contact to Z Electricity in June 2024. Similar pricing - still 3 hours free, from 3am to 6am, as well as half price electricity 9pm to 7am. But the main change is we've moved from a quite low but safely predictable 8c/kWh solar export price - to the rollercoaster of the wholesale spot price. That means we earn whatever the spot price is at the time and it changes every 30 minutes.  Spring solar export rates approached 0c/kWh but in summer it's been up around 20, 30 even 40c/kWh. We were often getting more for exporting solar power than we paid for importing grid power. February's bill was negative $95!

How is our Payback? How have things changed in the last 3 years?

4½ years more and the panels are paid off

There's been ups and downs, but the payoff has stayed fairly consistent at 8 years. 

Is this modelling is breaking down because of inflation? Power prices are going up, a larger power price will make it look like the panels are saving us less when they're actually saving us more, right? But turns out that's not happening after all. I looked at how our prices have changed over the years and because we've managed to juggle plans to our advantage we're actually paying roughly the same for power as we were in 2022.

In terms of how our panels are doing, we aren't seeing any degradation in the solar panels either which is great. Certainly nothing visible that we can discern from variations in weather. We'd expect this given that they have a 25 year warranty so any noticeable degradation after 3 years would be quite a worry.

Annual variation

We've had the panels long enough now to see how they perform in winter vs summer. 

2024 seems like a 'typical' year - 773kWh in January compared to just 200kWh in June. 75% less! That 25% of midsummer generation is still enough to keep our daytime power free-ish, when the heat pumps aren't warming up the place. We get a bit of power trickling in even on cloudy and rainy days. This is a good reason to over-spec your system though - how much power do you want to bring in, even in mid winter?

We bought an EV!

This will change things! In March we bought an MG ZS EV. It's got 320km of range and recharges from empty to full in about 24h on a trickle charger, and from 20% to 80% in 30 min on a fast charger. 

For instance, when Angela drove it back from Christchurch to Wellington, it needed one fast charge in Kaikoura. There are now plenty of fast chargers in NZ and it's charged up before you know it - 30 min is not quite enough time for a coffee and a muffin. 

24h on a trickle charger sounds like a long time, but it really isn't - because we don't commute in our car, it stays parked and plugged in in the garage and that basically means it's fully charged whenever you get into it. In fact because apparently it's slightly better for the car to not leave it sitting with a 100% charged battery, the issue is more managing it to not charge up fully and also to use the free power or the cheap power to charge it. None of which is actually necessary but it keeps me entertained. I'm turning into my Dad, who insisted on pushing our car around on the driveway because it was better for it than cold starting it.

Did we buy a battery yet?

Well, no. But my neighbour just told me about how prices are still trending down down down:

The lowest automotive prices are down to US $53 per kWh for a cell, and about US$75 in a vehicle battery pack. Might be an oversupply as EV sales are down in some markets

They are the later LFP chemistry which is far less fire prone

So A$1000 per kWh for Tesla Powerwalls is extreme, and other storage batteries for solar also look way overpriced.

I'm still hopeful to see 10kWh batteries available for much cheaper soon - which is all we need to capture a day's solar to use in the evening, and cheap/free overnight electricity to use in the morning. $1000 NZD, not $10,000 NZD would be a good price, and I'd be more than happy with second life batteries out of a parted-out EV. There is a bewildering array of batteries available now, this market is finally heating up like it should do.  But 50kWh of home battery storage is still a lot pricier than our MG with a 50kWh battery - and it doesn't come with a free car. That seems ludicrous.

I did some reading and seems like it's mainly because it's a niche market still. Folks ran through the inverter and installation costs (should only be a few thousand, certainly not up to the cost of a whole car!), interspersed with other folks with the expertise to build their own system, and had, for $1-2000 and showing their aliexpress receipts. 

We've just spent a week with Tim and Michelle in Townsville which was great fun - a battery is a no-brainer up there. Lots and lots of sunshine, zero and even negative solar export rates because everyone's doing it, and AC that runs all day and all night. The Aussie government is talking about subsidising batteries (as an alternative to building more power plants!) and like solar, anything the Aussies do creates a more mature market that we Kiwis can tap into.

Anyway, we are getting more than enough return selling our solar back to the grid right now. We now have backup power with the V2L cable that came with our MG - in other words, we can run our fridge and phone chargers off the car for a few days. So there is no point in spending any money on a battery. I will keep watching with interest.

Heating days

My work colleague, with a ducted heatpump system, has discovered 'heating days' as a metric of  electricity usage - especially if a big portion of your usage goes on heating.

This graph shows kWh usage of his heat pumps (the stacked bars) over the last 2 years, and the line is the “heating degree days” (HDD), which is the cumulative number of hours where Wellington was <16C.

The 'Heating Degree Days' line is, as you can see, a good predictor of actual heating energy usage. July 2024 bucks the trend as he went on holiday to Aus for 2 weeks 😊.

'Heating Degree Days' is also a good way of visualising whether efficiency gains have worked - has adding insulation or more efficient heating had an effect on your power bills when you adjust for Heating Degree Days?

https://Degreedays.net is his source, using NZWN as the weather station. Also lots of links to articles on that site to learn more.

The Wednesday that felt like Thursday

 Hi,

Yes - it continues through the week. Baffled every time I wonder what day it is.

Needed this snack - ta AJ

It was quite delicious

I was peckish at work and remembered AJ jad given Mike a bar for me ages back that I had in my bike pannier bag. So I tried it. And it was delicious. Turns out it comes from Aus (I know the brand - I used to eat that muesli for breakfast).

Made sourdough

Met Mike at 5.15pm outside work and put my bike on the back of the car and drove home. Mike had a meeting to attend after work.

I got home and fed the cats and myself. And watched some YouTube while I baked bread for Karin's leaving day today (Thursday).  Waaaaahhh. I do not want her to leave - she is such a mighty presence. And such good fun.

Off to bed when Mike and Christine got home at the same time. And they stayed up chatting away for ages. I was asleep when Mike came to bed. No clue when that was.

Up early to ride in for my gym session with Quentin. And Mike is sleeping in and missing his session. 

Hope you have a great day. Happy birthday today to Benjamin.

Love,

Angela

The Tuesday that felt like a Wednesday

 Hi,

So confused. Now it is Wednesday it really should be Thursday. I can't believe I still have another whole day at work.

French Kiss cart iced latte

Yesterday was interesting. Got pics from Juliet from her accident. They are not fit for any blog without some sort of health warning. A lot of people have felt very ill when they see the thumbnail and do not ask to see the pic enlarged. Horrific injury from slipping on a step in the bush. I hope she heals up well from that.

Then rode home after work. Met Mike and Andrew and got the Subaru sorted to head over to help Christine shift out of the house she lived in with her ex partner. Quite the excitement as she was hoping he stayed away to help her move out without any confrontation. We did not see him - so that was good.

Got to our house and Andrew and Mike piled the trailer contents into our garage. I can still get my bike in and out and I reckon I can do a workout in the gym. But maybe just one person at a time now. I got Christine sorted with a fresh bed and pyjamas and a toothbrush and a nice cup of tea.

She had some frozen meals so we defrosted chilli beef and they all tucked into that once the garage was full and the trailer dropped back at the petrol station in Taranaki St.

Hopefully she slept well. I did! Up to ride in this morning for a PT session.  Deadlifts.  80kg. 3 reps x 4 sets.

Work looks a bit busy. Start of sprint day. And then home to make some tea. I think Mike has something on tonight. But he is WFH today.

Have a great day!

Love,

Angela

The Monday that felt like a Tuesday all day!

 Hi,

I have no idea why today is not actually Wednesday. So confused this week. Anyway - I had a mighty Monday. Didn't catch up with Iona though - our schedules just didn't line up.

Mike got his medal wall updated in the weekend, after Sydney.
He was only supposed to do one half marathon as a bucket list thing.

I took Mike's PT session Monday morning as he took the car in to get a few things checked. And then at lunch time, Juliet came over and we did 67.5kg deadlifts. Huge effort.

Juliet was keen to get some forest bathing in, so I told her about the flax clearing loop I often do in the Otari Wilton bush. So off she went.

I was back at work when Jason pinged me asking what I did to Juliet.  Turns out she had fallen on the walk on a step and cut a huge gash almost to the bone. She is now off work for 2 weeks as the deep cut needed 16 stitches and she can't afford to get any infection.

OMG.

After work, I got tea ready (well, most of the tea) and then met Barb for a workout in the garage gym. Yep - 3 workouts on Monday. We followed an app she has - she usually goes to Les Mills and finds a spare spot to do it. But I think she enjoyed the garage gym - so maybe we can do it semi regularly. It was fun - and hard work.  1 hour.

Dropped her home and then back to finish cooking tea. And watched some Words Unravelled and then bed.

Up to ride in this morning. Bench with Quentin. 40kg 3 reps x 4 sets. And accessories. I am now dead.

Hope you enjoy your day!

Love,

Angela

The weekend in Wellington

 Hi,

Busy weekend in Wellington. Friday saw me walk into town to meet Maureen at Margies for brekkie. It was a bit damp with drizzly rain. 

Friday iced latte at Margies

Hey there!

Got my haircut after that and then walked back home. Spotted some nice toadstools on my way back up the hill.

Toadstool on my walk home

Pinned by cats

Moxley happy

Got pinned by the cats for a bit. But it was the day to stay in. After lunch the rain really lashed the house. 

Saturday saw Mike get up for Park run. Then after that we headed to Mike's mother's unit to collect her and then Sally for their airport connections. Saw them safely away and popped in to see Kara. Walked Rasta. Stayed for takeaways.

Walking Rasta

Ferry coming in

Hey Toby!

Sunday we got up for a run. The loop through Northland tunnel and into Otari bush. Such a good loop. I was a tad faster than last time.

Waterfall in Otari bush

Sweet Axe

Wally rang and said Chelsea was too hurt to go to Sweet Axe with the family and did one of us want to sub in. So Mike jumped at the chance. We hurriedly got changed and drove in. Made it just in time. And Mike was very good at axe throwing. As were a lot of the Sampsons. Lesley and I will be very protected in any zombie apocalypse. 

Toby rang me for Mother's Day while there was a lot of axe throwing happening. Good to see him and Tessa. Thank you wee Toby for making my day special.

Toby called me for mother's day

Brennan & Wally

Jase and Mike

Single handed Mike throw

Jason has good technique

Viking Wally

Back home after a quick Moore Wilsons diversion and off to Tawa for tea at Helen's house with Iona. Delicious. Good to catch up on the latest there.

Just beat it!

Back home and not long out of bed for us. Mike is now taking the new car in for a few checks. The back seatbelt is a bit fiddly to put on. And there is a wee chip in the back of the bonnet. Things like that. Mike got the V2L  to work - so yay!

Enjoy your day!

Love,

Angela

The Wednesday with family dinner

 Hi,

I got my flu vaccination at lunch time today. Yay. Work has a voucher for it and it was easy. Rocked up to the pharmacy and waited 5 mins and got it all done.

Mike and I bussed home after work and fed the cats and drove out to Petone to meet everyone for family dinner. Polly is up this week and it was so good to see everyone. Andrew is fresh out of the bush and John and Benjamin were there to update us with their latest news.

Bella Italia dinner

Home after a lovely dinner and straight to bed. Up for a bus ride in - my driver was steady and sure. But slow. So I ran from the bus stop to the gym and was only 1 min late. Phew!

Deadlifts.  80kg. 4 reps x 4 sets. Not too bad.

Then into Smith the Grocer to meet workmates for brekkie.

At brekkie

Iced latte at Smith the Grocer

Had a good catch up with them, then into work to start the day.

Love,

Angela

The Tuesday that was working from home

 Hi,

The wind got up through the evening on Tuesday so as we tucked ourselves into bed, I said to Mike I would bus in with him.

Smudge watching our mahi carefully

Supermarket iced coffees

The world is finally catching up with me

Mojo iced latte

Did my PT session with Quentin.  Bench. 37.5kg 5 reps x 4 sets. And then brekkie with Mike at Mojo in Brandon St. Was supposed to meet Juliet and Barb for brekkie but Goods in Tinakori was too far for me to make it.

Enjoy your day!

Love,

Angela