Solar, central heating and EV

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#2920393 30-May-2022 14:30

As mentioned above, charging an EV using batteries in your home may not be a good idea as it will wear out the batteries faster. Better to use it for your home and you will have some left over for a potential power-cut.

Personally I have just installed a 3 kW solar system (saving N and NNE) with 10 kWh of batteries and a 5 kW inverter for $16,000.

I also use Contact Energy's Good Nights plan (full disclaimer there is a referral code for $100 for each person in the link), where they give you free power between 9pm and 10am every single day, so I get free EV charging for my Tesla every single night, as well as that, I turn on the heat pump, dishwasher, dryer and use the shower. So it may be better to do what I have as one option?

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#2920411 30-May-2022 15:05

I spent $36K inc LG Neon 2 panels, SolarEdge Inverter and Telsa powerwall 2 in mid-2019. I absolutely love it.

First thing on the Powerwall. Its more than just for a power failure. The "peak load" I think is about 7kwh. I have turned on heat pumps, oven and had zero issues. I wanted a system that had me "off-grid" all summer and with a normal power supply as a backup. We use about 20-25kw a day normally so it needed to be beefy. Almost 2 years in I am still very very happy. We have multiple computers and everything just works. You would not know we were running off the powerwall unless I showed you the app. Summer we are 99% off-grid.

I spec'd the solar system to be within 3% in 10 years. Sadly LG have now pulled out but for me it was worth the extra as many systems have a big drop off over time (panel efficiency and panel degradation). The powerwall has a guarantee of I think 80% in 10 years. So far with software tweaks there has been little sign of any degradation 2 years later. May 26th I discharged 12.4 kWh so. I have read a few articles with most people very happy (occasional person with issues). A lot of early data was using the Model 3 car numbers.

I am pretty sure the Powerwall is about $18k. If could I would add another one. If I move I will get the same or as close setup. My main drivers were the green factor, that it can be a selling feature (with the right system), payback on power saved of around 4k a year and that QV would and did add the full value to the ratable value meaning I can justify that selling feature in sale value. I love getting my powerbill now. Not many can say that :)

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#2920439 30-May-2022 15:41

tripper1000:

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!

I've driven a few. But sliding around on flat seats with no lateral support and body roll aren't my thing.

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#2920442 30-May-2022 15:43

Quinny:

I am pretty sure the Powerwall is about $18k. If could I would add another one. If I move I will get the same or as close setup. My main drivers were the green factor, that it can be a selling feature (with the right system), payback on power saved of around 4k a year and that QV would and did add the full value to the ratable value meaning I can justify that selling feature in sale value. I love getting my powerbill now. Not many can say that :)

Not sure I see that as a positive.

Richard rich.ms

martyyn

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#2920444 30-May-2022 15:43

MikeAqua:

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

The wood burner is great, but I'm sick of getting multiple loads in every year, sick of paying through the nose for it in the middle of winter and sick of having to set it all the time and wonder if it will make with through the night.

There are also plenty of comments from people online saying their heat transfer systems are rubbish.

Our European roots are calling for radiators :)

wellygary

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#2920458 30-May-2022 15:56

martyyn:

The wood burner is great, but I'm sick of getting multiple loads in every year, sick of paying through the nose for it in the middle of winter and sick of having to set it all the time and wonder if it will make with through the night.

There are also plenty of comments from people online saying their heat transfer systems are rubbish.

Our European roots are calling for radiators :)

What are the problems you want solar to solve?- Do you want to be off grid? or just cutting down the bill every month?

If you are looking at heating a house, you can run radiators off solar, either via directly heating the water, or via a Heath pump water heater system.

But it all costs $$$

You can also heat water from a wood burner via a wet back, but it sounds like you are over lugging wood... you could always go down the biomass boiler route, pellets are the cleanest and easy to automate via a bulk hopper

But again its a $$$/reward equation

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#2920631 30-May-2022 20:42

wellygary:

What are the problems you want solar to solve?- Do you want to be off grid? or just cutting down the bill every month?

Not really looking to solve any problems just exploring all the options based on what we want to do.

The conversation started when we realised going to an EV for my wife would save us $5k a year in fuel and that's only likely to get higher.

Then came the desire to have central heating because our house reno is not going ahead. But we can still do smaller parts of that whole project.

Then came the question of whether we could power it all with solar.

Then came the question of whether it was financially viable to any or all of these things.....and here we are.

tripper1000

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#2920774 31-May-2022 10:34

A fundamental challenge for solar powered space heating in winter (or any other solar system) is that solar production drops off sharply due to the shorter days and lousy weather.

The "excess" solar I have for water heating is primarily a summer thing as I increased the number of solar panels to better keep up with the loads in winter (batteries used to run down after 4 or 5 days of bad weather), which means in summer I have/had capacity going begging.

To quantify it, in summer my 3 kw system (facing NNE at 22deg incline - so sub optimal) will make ~14 kw on a sunny day but at the moment, IF the weather is perfect it might make up to 6 or 7 kw. With the overcast weather in the last week, it has made less than 1 kw on some days. (my power bills in summer can get down so $45-$55 but up to $150 in winter, using a log burner as the primary heater).

If you are doing it for fun/learning etc and have lots of space for solar panels, there is no reason why you couldn't have a tonne of them to do space heating in winter but you're talking about a lot of solar panels. If you're doing it for environmental or economic reasons, there is probably more bang for your buck in other methods (passive heating, insulation, double glazing, VDS etc).

Quinny

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#2920780 31-May-2022 10:48

richms:

Quinny:

I am pretty sure the Powerwall is about $18k. If could I would add another one. If I move I will get the same or as close setup. My main drivers were the green factor, that it can be a selling feature (with the right system), payback on power saved of around 4k a year and that QV would and did add the full value to the ratable value meaning I can justify that selling feature in sale value. I love getting my powerbill now. Not many can say that :)

Not sure I see that as a positive.

Anyone who was a rebuild or had their home written off in the Chch quakes will know what a slippery trap that view is. Your insurance and house valuation are all affected if you do not add. Equally, as Solar is fixed to the roof it can fall under your house, not contents policy. As to this increasing rates, the common reason most people do not update QV only a small proportion is affected (Selwyn I think is 30% is based on house value) as most rates have a fixed component now for services provided. I was a full rebuild, full payout including a 70k contents claim. I was very very happy I had correct insurance and rates vlauations.

MikeAqua

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#2921300 1-Jun-2022 10:14

martyyn:

The wood burner is great, but I'm sick of getting multiple loads in every year, sick of paying through the nose for it in the middle of winter and sick of having to set it all the time and wonder if it will make with through the night.

There are also plenty of comments from people online saying their heat transfer systems are rubbish.

Our European roots are calling for radiators :)

I hear you on the woodburner. I miss having one, but then I don't. In a dream house I'd still have a small one with gas kindling system, for ambience. But otherwise radiators as far as the eye can see.

Heat transfer systems are often uninsulated foil ducting that runs through the roof space. Hopeless.

Our heat transfer was a by-product of a well designed smart-vent system. Which used an air to air heat exchanger for heat recovery (all insulated ducting). The installer cleverly designed it to move air through the house from the sunny areas (rooms that typically got too hot, even in winter) to the cool areas. I was sceptical about his predictions of how much difference it would make but it was truly impressive. If you have a sunny part of your house and a cool part this is well worth considering.

Mike

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#2921393 1-Jun-2022 13:03

martyyn: The wood burner is great, but I'm sick of getting multiple loads in every year, sick of paying through the nose for it in the middle of winter and sick of having to set it all the time and wonder if it will make with through the night.

There are also plenty of comments from people online saying their heat transfer systems are rubbish.

Our European roots are calling for radiators :)

The home we moved into a few years ago only had a fire place and we relied on it. While the level of heat output and the ambience is great - it is actually quite expensive to operate even when you get a good deal on wood. I figured that in a year we'd need at least 10m3 of wood. We can only store 6m3 at a time, so as you say you need to order more at full cost and that pushes you over $1k for wood. I don't even think we'd get to spending half of that on operating a heat pump. The wood becomes all the more expensive too when you're trying to buy hardwood and not just churn and burn soft stuff.

End of last year we installed a heat pump in the lounge and we use it when it's not cold enough to light the fire, and in the mornings after the fire has gone out. We've paired it with a Sensibo which detects when the lounge has dropped below 20c (when the fire has really gone out) so it's made the fire more of a luxury, and gives us the convenience of the heating.

If we didn't have the fireplace we'd need to look at a multi-room set-up or ducted system.

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martyyn

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#2932605 21-Jun-2022 16:04

Quick update:

We bought an EV was last week. The diesel price increases in the last two weeks may have already saved us another $600 for the year so it just made sense.

Solar. We've had two price "estimates" and have two site visits coming up. An off the shelf option from a well known provider and a bespoke system from another who provided a fully off-grid version for some friends. We're looking at $8-10k plus $2-3k install for 12 panels and a decent inverter (which isn't really going to maximise what we can do). But another $12-15k would give us a few more panels and 10KWh of batteries. The savings we can make from the first option looks to be a no-brainer, the battery option needs more thought.

Central Heating. This has been a real pain. Very little contact from the people we've contacted and vastly different prices from those we've spoken to. Gas radiators would be $17-20k, but as we don't have gas in the street we would likely go through 3 or 4 bottles a month at $100 a bottle. An Air to Water Heat Pump on the other hand would be close to $40k ! That's a lot of gas bottles/wood. In fact we could buy 20 years of gas bottles and still not recover the cost on the heat pump.

It's been tricky to understand all the pros and cons to each system because each supplier is convinced theirs is the best and the others are rubbish.

Given the costs I'm seriously thinking of just buying a few oil column heaters and leaving them on all day.

eonsim

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#2932749 21-Jun-2022 19:28

martyyn:

Solar. We've had two price "estimates" and have two site visits coming up. An off the shelf option from a well known provider and a bespoke system from another who provided a fully off-grid version for some friends. We're looking at $8-10k plus $2-3k install for 12 panels and a decent inverter (which isn't really going to maximise what we can do). But another $12-15k would give us a few more panels and 10KWh of batteries. The savings we can make from the first option looks to be a no-brainer, the battery option needs more thought.

So 4-5kW system with regards to the Solar? If you've got the roof space and have an EV then I'd suggest adding extra panels. I certainly haven't heard anyone complaining they had too many panels, but many people end up wishing they had a few/lot more.

With regards to central heating a colleague with a new off grid build went for underfloor heating linked the a very large custom built hot water cylinder, they then dump all excess solar energy into the hot water cylinder (just using a conventional heating element I think) and circulate it through the floor for heating. Maybe it's worth asking around to see if someone can do something similar but pump the water through radiators...

With a big enough solar system except for the wettest days in winter you would probably have enough solar power to keep the house warm either with such a system or a big heat pump setup. And on such days with a big enough system you may still have credit from the power exported in summer to cover the cost of the grid power.

Also any particular reason your not looking at a ducted heatpump system or multi-headed heatpump rather than radiators?

martyyn

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#2932859 21-Jun-2022 20:23

Yes, 4-5kW. 12 panels would probably see us generate enough for 8 months of the year but the analysis of where we are shows we'd be selling ourselves short so we'll likely go for 16-18. We have the roof space and the suppliers suggested getting as close to the inverter max as possible for as long as possible throughout the year.

We're keen to look at ducted heatpumps as well but getting people to respond is not easy. I've always thought heating water was more efficient and economical than heating air and pumping that around.

I also remember the fuss when we had our HRV installed years ago that it wasn't heat recovery (it's not) and that the heat pumps attached to them we're rubbish.

But like I said, it's hard to get the pros/cons of each system. More often than not the person who answers the phone knows very little, the person who can answer your questions doesn't return your calls because their too busy and if you do get someone they are often just sales which keep pushing the same stuff you read on their websites.

If anyone has any ideas for ducted heat pumps let me know.

timmmay

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#2932861 21-Jun-2022 20:35

martyyn:

If anyone has any ideas for ducted heat pumps let me know.

Have a read of this thread, then reply here (not there) if you have questions, or start a new thread and tag me if you want my opinion. I'm not an expert on ducted heat pumps, but I have one.

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