Solar, central heating and EV

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martyyn

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#296198 29-May-2022 12:45

I know very little about these subjects but it's something we've decided to look at as our reno has been put back for another 12 months. TLDR further down.

Solar:

We have some of the highest hours of sunlight in the country (so I'm told) and the roof over the four double bedrooms faces NNW, no obstructions so it literally is from sunrise to sunset. We also have a 6x7m garage away from the house.

Central Heating:

House is pretty much split down the middle by a wall and hallway. One side has an old school wood burner heating the open living/dining/kitchen to 450C but only 425W wall panels in the four double bedrooms on the other side. They do ok most of the time but are too hot on the days we have all day sun and struggle if we are out all day and leave them off. If the wood burner goes out at night the living areas are freezing in the morning. Using macrocarpa we can have it go all night but even at this time of the year we don't need it going from 10am until 4pm.

The house is insulated top and bottom and we have an HRV with an outlet in each bedroom, plus two in the living/dining/kitchen. Condensation is nil.

EV:

Our office is a 50km round trip which my wife does 4 days a week. No charging available once there, but she will need the ability to do closer to 200kms a couple of times a month.

WAF:

I cant emphasise this enough. WAF is extremely important and I will pay extra for ease of use.

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TLDR;

Obviously solar can power the house and adding a battery can power both the house and charge the car.

But is it possible to run central heating from a battery during the times solar is not generating ?

Can it do water heating as well ?

Or are we looking at solar to charge a battery which then runs the house/water/EV, with the central heating running from the grid ?

I'm not looking for the techiest solution or the cheapest. We're at the stage in life where we want to be comfortable and don't mind paying for ease of use. I'd like to "set and forget" the house temperature, maybe different temps in different zones (but not essential), maybe the ability to change it via an app (but not essential).

What I don't want to be doing is checking an app multiple times a day to see if it's the right time to do the washing, or put the dishwasher on, or charge the car. Our main use of the whiteware is outside normal peak hours because I'm usually at home.

Of maybe we are just better off saving the capital and buying the heating and EV and doing it all from the grid ?

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Scott3

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#2919949 29-May-2022 13:33

The name of the game in grid tied solar is to self consume as much as possible. for export power you get paid 6 - 8c, but to import power you are paying cira 20 - 30c. Solar systems are financially viable at 20-30c, but not at 6 - 8c.

My comments in bold.

Obviously solar can power the house and adding a battery can power both the house and charge the car.

But is it possible to run central heating from a battery during the times solar is not generating ? Yes, But there are constraints around run time from the size of your system. A tesla powerwall (cira $15k I think) is 14kWh, and has a max output of 5kW. Say a central heating system drawing 3kW would drain it in under 5 hours. Of course you can gang multiple, but at $15k a pop, the cost would add up fast.

Can it do water heating as well ? Yes, but doing so would be illogical. A 300L cylinder (worth say $3k), heating 15 degree water to 65C, stores 17.46kWh of energy. Obviously much cheaper to simply store this energy in hot water, than to store it in a battery. An upgrade to a 300L cylinder is 5 times cheaper than a power wall. With a PV solar setup, either a simple timer, or a smart solar diverter can be used to get the hot water cylinder to heat in prime solar hours. Also could do it old school thermal (evacuated tube) solar for water, but it seems a lot of people with PV setups just use them.

Or are we looking at solar to charge a battery which then runs the house/water/EV, with the central heating running from the grid ? In the vast majority of cases, you are looking at a grid tied system. In short, the solar generates whatever it can, The house's consumption will use this first. Any solar that is left over will be exported to the grid, any shortfall will be imported from the grid. Add a battery into the mix, and it will monitor the movement to / from the grid, and try to keep this as close to zero as possible. I.e. it will charge itself to soak up power that would otherwise be exported, and discharge itself when power would otherwise be imported. Hence meaning you can self consume more of your own power, avoiding the costs of the import / export spread)

Of maybe we are just better off saving the capital and buying the heating and EV and doing it all from the grid ? Each of those items is separate, and should be evaluated as such.

- Central heating is primarily about comfort. Despite heat pump systems being 3x as efficient are resistance heaters, often people find their overall power cost is similar or greater due to a combination of the Jervon's paradox, and the ability of a central heating system to acutally heat the house properly. Evaluate the heating upgrade under this basis: If the improvement in comfort & convenience is going to be worth the capital cost, then go ahead.

https://en.wikipedia.org/wiki/Jevons_paradox

- The EV - A combination of financial & environmental. Replacing fossil fuels with 80%+ green power from the NZ grid is a clear win from an environmental perspective. Also a lot cheaper to run in the current environment with RUC's zero rated. Capital cost is obviously higher than a petrol car. If you are shopping for a new car, the 200km range requirement is pretty easy to meet, with a decent safety buffer. Heaps of options, but at the cheaper end of the spectrum are the MG ZS EV (new shape has a 330km rated range), and the Peugeot E-208 (362km WLTP rated range), Ioniq (311km WLTP rated range). Personally I think this offers the biggest bang for buck, but a lot of the outcome depends on how much your spouse likes the current electric offerings, and how efficient their current car is.

Peugeot e-208 (2020-2021) price and specifications - EV Database

E-208 $53,365 +ORC after rebate.

- Solar - Mostly financial, with a bit of feel good factor about self sufficiency. (A study has shown that in a NZ context solar dosn't actually reduce emmisions as the grid is so green allready, and it's displaces renewable baseload genration in favor of non-renewable peaker plants). In terms of financial, as a general rule, batteries are too expensive to give a financial return. Solar is, but sized such that you self consumer a decent chunk of your generation. i.e. they are economic if you are generating power you would have otherwise purchased at 20c - 30c / kWh, but not if you are selling to the grid at 6 - 8c/kWh.

martyyn

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#2920055 29-May-2022 14:47

That's great, thanks @Scott3. If I understand what you're saying we just need to adjust how we're thinking about it.

Our current "consumption" is the house (cooking/water/washing/etc) + heating + car.

Solar could meet all of that consumption if we buy enough panels and batteries. But generation is not 24x7x365 so it's unrealistic regardless of how much money we had to spend.

Instead, we get as much power from solar as we can and store it in as big a battery as we are prepared to pay, knowing the rest we will be buying from the grid. So it comes down to how much we want to spend to replace each item (house, heating, car) and whether the savings warrant it.

Looking around solar with a 5Kw battery would be around $20-$25k, is that fair enough ?

Our builder has said central heating would be around $20-$25k (140m2, four bedroom, 1960's with insulation top and bottom).

Our current daily is a diesel doing 7.2l/100km. My spreadsheet tells me at currently prices, including RUC's, doing 20k kms a year, an EV would save $5000 in fuel alone. Servicing could add another $1k to that total.

So an EV would save $6k a year and keep saving money as fuel prices increase. Five years of that pays for the solar, another five years pays for the central heating. There will have been power savings on top as well but another ten years saves another $60k which covers the car.

So in 20 years we could be cost neutral and needing to go through the whole process again as the panels and battery will need replacing, or is that too cynical :))

eonsim

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#2920060 29-May-2022 15:18

Based on your description of a NNW facing continuous roof you should be able to get a decent number of panels on there. One advantage for NNW is you will tend to get a bit more power later in the evening as there will be a slightly better angle of light from the sun vs true north or NNE.

In general you should be looking at a grid tied solar system, or grid tied with back up rather than a full off-grid system on an existing house with a grid connection. Typically straight grid tied systems with out batteries have a payback period of 8-12 years (depending on your use and location) with a life-expectancy for the panels of 25-40 years. As said above when designing such a system you really want to optimise it for self consumption rather than for exporting power back to the grid. You can get export rates up to 16c in certain cases, but the top normal rate is about 12c/kWh (Electric Kiwi, and a couple of others) with the typical rates in the 6-10c range.

A typical Grid tied solar system with 5kw of solar panels is likely to be between $11k-17k depending on what panels and extras you add. Such a system will likely generate around 30-35kWhs on a sunny day in summer, and 10-15kWhs on a sunny winters day. During a day of heavy rain though it may only generate 1-3kWhs. Also a 5kW system will probably generate no more than 4.5kW's at midday in summer and 3kW at mid-day in winter, which one has to keep in mind when working out how much power usage they can off-set.

Systems with batteries tend to cost $10k-17k more (depending on capacity), probably on the lower side of that if you go with a hybrid inverter and a DC battery storage system. In such setups the inverter can both charge and draw power from the batteries, which makes things more efficient and reduces the system cost as you don't need a second inverter for the battery. The alternative option is a AC battery system like Tesla power wall which costs around $17k, with ~13kWhs of usable power. AC batteries tend to be more expensive as they need a second Inverter than can convert AC power from the grid/solar to DC power for storage and then back to AC power when you want to use it. AC systems tend to be less efficient as well and you only get ~90% of the power you put into the battery back out. While a DC system uses the DC power from the solar panels and thus only needs to convert it to AC power when you use it and thus you can get ~95% of the power you put in back out. Solar systems with batteries tend not to payback their cost before the warranty expires (on the battery), even with the ability to store and self consume more of your power.

The main reason for going with a battery is you want power in case of a blackout, or you want to go off-grid as much as possible, or you can't get a grid connection. If cost isn't a concern then a battery or two can be nice to have just for the knowledge you'll never lose power.

In general with solar the key thing to maximizing your return on investment is the ability to load-shift power usage to sunlight hours. This can work really well with with things like hot water cylinder heating, spa, swimming pool, washing or drying clothes, and charging an EV (if you WFH). If you have timers attached to these systems or solar diverters (good for hot water) it quite possible to move a large proportion of your power use on to the solar. Ideally in a grid tied system you would get a power plan with a decent export rates and low overnight rates (Flick, Electric kiwi Move master etc). That way you shift what you can to when your solar is producing well, and shift other things like the EV (if working at the office), dish washers etc to run overnight when the grid power costs less.

This is especially important if your house only has single phase power, as some lines companies won't allow you to export more than 5kW back to the grid. Thus you tend to be limited to solar power systems up to around 8-12kWh. The inverters will then be setup so they will only generate 5kW's + what your house is using. So if you are using 2kW in the house then the solar system will only generate 7kW's even if you have a 12kW system, with 2kw used by the house and 5kW exported. If you have 3-phase power you can typically do 3x what ever the single phase limit is, so export up to 5kW per phase + what ever your house uses.

The other thing with solar is put as many panels as you reasonably can on at once. For example if you look at how much power you use per day and adjust it to your likely future use with EV + Central heating and decide a 6kWh system would work for you then add 30% more as inverters can take upto 30% more panels than the amount of AC power they can generate. The advantage of this is with 8kW of panels on a 6kW inverter you'll never generate more than 6kw at one time. However the amount of time during the day at which you can generate 6kW will significantly increase as at times when there isn't enough light to generate your full 6kW the other panels will compensate for upto a 30% less than ideal light. As such instead of generating peak power for 3-4 hours at day in summer you may get 6 or more hours of peak power.Also this helps compensate for the gradual loss in generation that all solar panels suffer. At 25 years top of the line solar panels will generate ~92% of there power rating, while average solar panels will be around 84% and the really cheap panels maybe 80%.

Just don't buy a 12kW system if your usage can be covered by a 6-8kW system as the export rate doesn't really provide that much benefit. But run the numbers your self based on how much power you might generate and use.

You can have a look at the NZ solar calculator to get a feel for how much power a system might generate for you based on your house location and how quickly it might pay off given your likely useage patterns: https://tools.genless.govt.nz/individuals/solar-tool/

Dingbatt

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#2920073 29-May-2022 16:41

Most of the stuff I’ve seen on batteries is 10 to 12 years (to 70%).

At the moment I am looking for a system that can have batteries added later.
As I understand it an AC system allows stuff to be added, a DC system not as easily as the panels, battery and inverter need to be set up for the particular system.

And then there’s micro-inverters, or optimisers, dual sided panels, different battery chemistries on top of what’s already being discussed.

On top of all else is something mentioned on an Aussie website. How much do you like tech, and dabbling in this stuff?

“We’ve arranged a society based on science and technology, in which nobody understands anything about science technology. Carl Sagan 1996

Scott3

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#2920182 29-May-2022 22:17

martyyn:

That's great, thanks @Scott3. If I understand what you're saying we just need to adjust how we're thinking about it.

Our current "consumption" is the house (cooking/water/washing/etc) + heating + car.

Solar could meet all of that consumption if we buy enough panels and batteries. But generation is not 24x7x365 so it's unrealistic regardless of how much money we had to spend.

Instead, we get as much power from solar as we can and store it in as big a battery as we are prepared to pay, knowing the rest we will be buying from the grid. So it comes down to how much we want to spend to replace each item (house, heating, car) and whether the savings warrant it.

Looking around solar with a 5Kw battery would be around $20-$25k, is that fair enough ?

Our builder has said central heating would be around $20-$25k (140m2, four bedroom, 1960's with insulation top and bottom).

Our current daily is a diesel doing 7.2l/100km. My spreadsheet tells me at currently prices, including RUC's, doing 20k kms a year, an EV would save $5000 in fuel alone. Servicing could add another $1k to that total.

So an EV would save $6k a year and keep saving money as fuel prices increase. Five years of that pays for the solar, another five years pays for the central heating. There will have been power savings on top as well but another ten years saves another $60k which covers the car.

So in 20 years we could be cost neutral and needing to go through the whole process again as the panels and battery will need replacing, or is that too cynical :))

Regarding solar with a 5kW battery, price will vary wildly. Things like how many solar panels, their quality, inverter size how easy your roof is to mount to, if you want the ability to run island mode, if you want a hot water cylinder timer or solar diverter, if you need RCD protection added to your existing circuits etc. But for reference I think you would need to double your estimate. A powerwall 2 (5kW continious, 7kW peak, 13.5kWh) is at least $15k alone.

In terms of your evaluation, I'm not a fan of how you are mixing unrelated things together.

For the EV, calculate the payback period of that purchase first. Say the tradeup cost to get an EV you liked was $40k, and you estimated $5000 savings a year (EV's while much cheaper arn't free to run). So an 8 year payback on that one at current fuel prices. (with the likely bonus of a more modern car, that will still have a lot of residual at the end of that period). Once the car is paid off, yes, you will have $5k of savings a year, that you can spend as you wish.

Central heating, just comes down to if it is worth the price to you. No payback period on this, but obviously great comfort. (Note if you don't have wall insulation this could be quite expensive to run).

With solar, @eonsim quoted a pay pack period of 8 - 12 years for a system with no battery. If you have the capital (and your roof isn't going to need major work in the next couple of decades), might as we go for it. Better return than money in the bank. I think generally batteries generally don't stack up financially in NZ, so the motive would need to be something else, like better self sufficiency, or the ability to keep power on in a power cut (with some power rationing to avoid running out the battery).

Feel free to do all three projects at once, but base each one on it's own merits.

richms

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#2920187 29-May-2022 22:37

Does anyone know what the current things are around export limiting your install? When I last asked (may have finally changed since then) vector didnt let you use export limits on an instalation, they would limit you to the total inverter output amount connected to your connection regardless of what the panel layout or string configurations would do.

This is why there were loads of installs done that were sized to clip considerably at peak production, because that's all they were allowed to have connected despite the fact there would be usage inside the property and it could be configured to never export more than you were allowed.

Richard rich.ms

eonsim

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#2920189 29-May-2022 22:43

Scott3:

If you have the capital (and your roof isn't going to need major work in the next couple of decades), might as we go for it. Better return than money in the bank.

One thing here I would suggest if your roof needs work in the next year or two, wait until that's done to install solar, or bring the roof work forward and install solar while your doing it. If the Roof is fine for the next 5+ years (not the 10-20) then get solar now, as you can always pay a couple of grand to get the panels taken down and stored while the roof is replaced, then reinstalled. It'll push the pay-back time out by a couple of years but still well worth it.

Batteries (unless the house is currently off-grid) is very much the deluxe option, your paying extra (quite a bit extra) for the ability to minimize your power bill and gain 100% reliable power (short of a massive storm taking out the local grid, and even then batteries + panels will still give you power to cover critical loads).

If you want to take a gamble on a faster pay back you can go Solar + Battery and switch to Flick electric, as they pay spot prices for exported power. Over the 6-9 months that's probably been closer to 16-20c per kwh, with occasional spikes to 40-50c per kwh. If you really want to get into trying to maximse your return on the battery or at least minimize the pay-back time you can look at using home-assistant or other automation to attempt to use your battery to follow the spot prices, and actually export from the battery when spot prices are above a certain level ie 20-30c, and it's only going to earn you a few extra dollars here and there. It's gamble depending on what spot prices do you could end up paying your battery off a bit quicker by exporting 4-5kwh hours at crazy spot prices or peak times over the next few years, hard to know.

eonsim

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#2920190 29-May-2022 22:46

richms:

Does anyone know what the current things are around export limiting your install? When I last asked (may have finally changed since then) vector didnt let you use export limits on an instalation, they would limit you to the total inverter output amount connected to your connection regardless of what the panel layout or string configurations would do.

This is why there were loads of installs done that were sized to clip considerably at peak production, because that's all they were allowed to have connected despite the fact there would be usage inside the property and it could be configured to never export more than you were allowed.

At least on WelNetwork in the Waikato it seems like you can have an export limit (5kw) set on the inverter and then produce your export limit + household load. A chap I know recently put in a single phase 11kw system on an 8kw inverter that's been exported limited to 5kw but as you can see from PVoutput regularly produces in the 6-8kw range when accounting for household load. https://pvoutput.org/intraday.jsp?id=99706&sid=87796&dt=20220527

richms

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#2920241 29-May-2022 23:23

eonsim:

At least on WelNetwork in the Waikato it seems like you can have an export limit (5kw) set on the inverter and then produce your export limit + household load. A chap I know recently put in a single phase 11kw system on an 8kw inverter that's been exported limited to 5kw but as you can see from PVoutput regularly produces in the 6-8kw range when accounting for household load. https://pvoutput.org/intraday.jsp?id=99706&sid=87796&dt=20220527

I guess I will find out soon anyway. Im going to give the go ahead to lighthouse to put the solar on my shed which is way more than I thought it would be but will get me enough to have a surplus during the day, which the 2ish kw on the garage doesn't do. Once the house gets reroofed will for sure have to upgrade the supply or look at battery to take the peak and move it to a more profitable time if I put solar on that.

Richard rich.ms

tripper1000

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#2920303 30-May-2022 09:59

I have an EV and a home built power wall (~16kw/hr) and 3kw of solar on the roof.

EV: What I save in petrol every month (coming from a 2L petrol and travelling about 12,000 km per year) easily covers my entire power bill, so just changing to EV was my biggest energy cost saving change. (In 2017 I was spending ~$2600 pa on petrol (would be $3400 pa at current prices), now spending $480 pa on EV power). Full disclosure: this won't always be the case though - RUC's will be applied to EV's in the near-ish future and after that it will be comparable or worse to a hybrid in savings - but the sooner you change the more savings you can make before the change! (you don't have to "Switch" as the media puts it and ditch the piston car - 2 car families usually keep a piston car as a) a security blanket and b) for the long trips/trailer towing etc. My fuel cost savings also easily cover the cost of insuring and registering my piston car that sits unused in the garage most of time).

EV's are nice to drive, much more refined than a piston car, much better performance with much less fuss.

Solar: I had grand plans to charge the EV from solar. But the above savings and the low cost to run the EV ($4 per 100 km) means you are sinking a lot of capital into trying to save on an already very small cost - there is no return on investment here. Long story short: storing solar in batteries and using it later (particularly for heating or EV (both heavy loads)) hammers your batteries and is false economy. The grid is simply cheaper than batteries when all said and done.

To get the most out of solar, you really need to be able to use it as you make it - not easy when the EV is at work in the day-time. I charge my EV from solar in the (sunny) weekends, but had excess unused solar on week days. So I build a circuit to put my excess solar into my electric hot water cylinder. This would be the second greatest energy cost saving I have made. The beauty is that water doesn't "wear out" like a battery so even if I scuttle the battery system, I can/will keep the water heating system. If you are building from new or renovating, it might make more sense to use thermal solar water heating (or both in series) - I only went the electric route to make existing assets use existing solar surplus.

You can do other things to save energy costs: like using the delay start on dish/clothes washers to run in the day time when solar is producing. I was already using the timers to run at night on the cheaper off-peak power, so it was not a major shift in strategy for me.

My solar-battery system just runs my I.T., refrigeration and washers at the moment (and the lights/whole house when there is a power cut!).

Nate001

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#2920307 30-May-2022 10:16

Thinking about solar only - First question to ask your self is why do you want solar? Is it for:

Cost savings? - Its a long pay back.
Sustainability/environmental? - As others have mentioned power in NZ is generally already quite clean vs other countries so that net gain is not much.
For self reliance off the grid?
For the fun of it/interest?

If your reasons are 3/4 then I'd say go for it otherwise unless you got money to burn its not worth it.

eonsim

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#2920333 30-May-2022 12:12

Nate001:

If your reasons are 3/4 then I'd say go for it otherwise unless you got money to burn its not worth it.

I'd disagree with this.

Using the solar calculator above on a 5kW system the estimated return after 25 years was +$24,000 after accounting for the cost of the system and the maintenance. That corresponds to ~4% interest rate per annum. Good luck getting that from a bank over that time period, and while you can probably get that from growth investment funds with substantially higher risk.

The calculator also only assumes 1.8% annual increase in power bills so the benefit is likely to be substantially higher than that (given 6% inflation currently)! And it was assuming the money was borrowed to pay for the panels (with interest costs included in the calculation).

Also while people keep saying NZ has a green grid that is only mostly true, in the last few months NZ has been running at ~70-80% renewable energy, the rest is coal and gas. While that may be better than many other countries it's worse than others and it's still a substantial amount of CO2 generation.

martyyn

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#2920356 30-May-2022 13:13

Some great comments here, thank you. A few answers.

@Dingbatt:
On top of all else is something mentioned on an Aussie website. How much do you like tech, and dabbling in this stuff?

---

To be honest, I'm over getting too involved in projects these days. I still want to have a good idea of what's being done but I'm at the stage of life where I just want to call someone in and have it all done with the minimum of fuss.

@Scott3:
In terms of your evaluation, I'm not a fan of how you are mixing unrelated things together.

Feel free to do all three projects at once, but base each one on it's own merits.

---

I hear what you are saying. Even if the savings on one project paid for another, if the second project doesn't make financial sense then what's the point ?

@Scott3:
If you have the capital (and your roof isn't going to need major work in the next couple of decades), might as we go for it. Better return than money in the bank.

---

Roof was replaced about 11 years ago, it shouldn't need anything for a long time.

@tripper1000:
EV's are nice to drive, much more refined than a piston car, much better performance with much less fuss.

---

Yeah, nah. I daily an BMW msport 320D with a manual 6 speed gearbox. It's an amazing daily (over 1100kms on a full tank) and an absolute blast to drive being manual with msport suspension and 350Nm. On the weekends it's either the 1990 535is or V10 M5 :)

@tripper1000:
Solar: I had grand plans to charge the EV from solar. But the above savings and the low cost to run the EV ($4 per 100 km) means you are sinking a lot of capital into trying to save on an already very small cost - there is no return on investment here. Long story short: storing solar in batteries and using it later (particularly for heating or EV (both heavy loads)) hammers your batteries and is false economy. The grid is simply cheaper than batteries when all said and done.

To get the most out of solar, you really need to be able to use it as you make it. I charge my EV from solar in the (sunny) weekends, but had excess unused solar on week days. So I build a circuit to put my excess solar into my electric hot water cylinder.

---

This is exactly what I needed to know and exactly what I can do being at home 3/4 days of the week. It also helps answer the next question. If we have solar and are generating extra, how do we use that ? This is why I wanted to know if we could power the central heating.

@Nate001:
Thinking about solar only - First question to ask your self is why do you want solar? Is it for:

---

Good question. A little of 1 & 2 really. We had planned a big reno but Covid and supply issues have scuppered that for the time being and it made us re-evaluate whether we want/need to spend hundreds of thousands on a house which will only have two of us in it in 4/5 years.

Another reason is the desire to normalise using solar and an EV not only for others but for our kids. We can afford it and an 8-12 payback is fine. But if it inspires others to think about their situation and what they can do then we see that as a good thing.

But this thread has done exactly what I needed. It's reminded me NZ's power supply is mostly green anyway and told me batteries aren't really viable for anything other than a power cut. We have had a couple of those recently but no harm has been done and it's certainly not something we are worried about.

tripper1000

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#2920389 30-May-2022 14:25

martyyn:

Yeah, nah. I daily an BMW msport 320D with a manual 6 speed gearbox. It's an amazing daily (over 1100kms on a full tank) and an absolute blast to drive being manual with msport suspension and 350Nm. On the weekends it's either the 1990 535is or V10 M5 :)

Pffst - an entry level Nissan Leaf (2018) makes 320 Nm at 1,000 RPM and holds it dead flat through to 3,250 RPM - ~~out (torque) performing the USA Spec 2019 BMW 320D M6~~ for width of the power band and peak torque, and without those 6 pesky traction & neck breaking gear changes (because it doesn't have a horse-power stealing gearbox!). Seeings how you're a Beemer fan, the BMW i3 (another entry level EV) makes only 250 Nm, but holds it dead flat from 1,000 to 4,700 RPM - a way wider and far more usable power band than many piston engines 😃 (they electronically limit torque below 1,000 RPM for the sake of the tyres).

I recommend you take an EV for a test drive!

martyyn:

This is exactly what I needed to know and exactly what I can do being at home 3/4 days of the week. It also helps answer the next question. If we have solar and are generating extra, how do we use that ? This is why I wanted to know if we could power the central heating.

For commercial grid-tied solar systems they make hot water solar diverters to put excess power into the hot water and EV solar diverters to vary the charge into the EV when solar is making a surplus. When demand in the house increases (or solar production drops), they slow the heating/charging down so as not to draw current from the grid.

Edit - see strike-out - getting my ft/lbs and Nm mixed up! 320D makes 400 nM, but still over a narrower rev range and it runs out of RPM at 4500 where as the Leaf pulls past this all the way to 9,000

MikeAqua

6807 posts

Uber Geek

#2920390 30-May-2022 14:27

If you have heat build-up in one part pf the house (currently due to a log burner) then consider a heat transfer system. In our first house in Nelson, we were able to use a smart vent system to move excess heat from the sunny rooms of the house to the cooler rooms. It functioned like central heating, to an extent . Everything in the house was warmed to a background temp of about 16C and the heat pumps heated the air on top of this. I had to trim/ventilate a few doors, to allow sufficient airflow for this to happen

Mike

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