Advice on Powerwall for new build?

[AndyEV]

Dear Tesla Brains trust,

I’m building a house at the moment, looking to stuff as many solar panels as I can on to it. Expecting 10-12 kW size. The house will be large (5 bed), double storey, but I have also similarly stuffed as much insulation, double glazing, passive heating/cooling as I can into it as well. Three phase has been connected already + appropriate electrical wiring/switch gear is in the plans for similar.

I’m expecting to start making decisions on a battery for installation in say May or June 2021 and am looking at a Powerwall 2 (or 3 by then?). We’d consider 2 banks if it made sense.

Being in Melbourne, had anyone got a PW2 installed and can give some advice on things to consider for a rank novice? At the moment, we have one M3, but may be expanding to include an MY in a few years time.

Thanks!

 

[EcoCloudIT]

@AndyEV - I have 1x PW2 (award from Tesla, thanks Elon) and it has really transformed our consumption of grid supplied electricity more than I imagined it would.

As if writing this email, a few facts:

• It's a sunny morning in Melbourne and we are bring in a little over 3.5 kW (8:25am). If the sun keeps shining then we will be fully charged by 10:30am - 11am
• House is consuming 0.5 - 0.7 kW….house was using more kW around 6:30am as the AC started up to base load warm the house to 19C in habitable only rooms, trade off between what my wife wants of 22C and what I would like of 17C
• We have 2x Tesla’s…a Model 3 (changed from Model S previously) and a Model X. As a family we've been all electric since 2018, myself since late 2015
• We have a 12 kW system on single phase

Our house/habits:

• We use an Actron Platinum VSP system, ensure you are using this type AC of system if you want one of the biggest drawers of energy to be considerably less (VSP is the key, only Actron whom invented it and Daikin whom pays a royalty on it have VSP)
• House is North/East facing, single story, 80 year old weatherboard cottage with a 33% pitched roof in Malvern East. We stripped it inside and out about 5 years ago, doubled the size and packed it full of insulation etc. etc.)
• We have automatic blinds around the house, including a large outside balcony area, that controls light (radiant heat) to allow more in in winter and less in summer
• We charge the cars off of excess solar when we can (of course COVID has made this easier than I think it would normally be during winter)
• We have of course changed all lights to LED (including dimmable chandeliers, those bulbs are expensive, well the nice looking bulbs that is)
• We only run the dishwasher etc. during the day
• My wife is an amazing cook and the ovens (yes 2x of them), the commercial exhaust fan (yep, that's a power hog) and a small fridge (sounds silly but it makes a difference, we shop often) etc. all get a working out often when the sun isn't shinning

Given all of the above I am amazed we have been virtual off-grid (in terms of power draw) all winter.

We have been 99% off grid today and the past week, 92% for past month and 91% for lifetime (we only got the battery at the start of autumn)

My advice, pack out the roof with as many panels as possible (go 2x PW2's if getting a 12 kW system and you have the budget), continue to do as you say and insulate etc., get as power efficient appliances as possible,.

Note
Look at using a Hebel Floor on the first floor if possible, not sure which stage of building you're up to? It will make a considerable difference on a two storey house (heat transfer etc).

EDIT: Oh, and of course make sure you use Tier 1 Panels installed from a reputable installer...pm me if you want to know whom I used. They specialise in heritage types of homes where the "look" is a considerable road block when it comes to our "better" halve bosses.....

 

[jamesgo]

We've had our Powerwall 2 for 3 years and it's been running fine. The key to remember is the 5kW continuous max in/out so yeah I guess 2 units should do the trick.

 

[Onshore]

Powerwall V1 here for 4 years and hasn’t missed a beat.

For a new build I would absolutely recommend a Powerwall and as large a solar array as is feasible.

My tip, is to get onto a Time of Use power plan if your provider offers it.

This means around 50c per unit in peak, BUT the battery covers the peak most days 1400-2000 M-F.

The ‘reward’ is that you get grid power for 11c a unit from 10pm -7am.

 

[AndyEV]

Thanks for the detailed explanation. It is a larger volume builder hence the difference in cost vs. specialist design - with the benefit of having some cash to spend on additionals.

We have also specified the ground floor with Hebel, but not the flooring, no option on that

Will PM separately, appreciate the help.

@AndyEV - I have 1x PW2 (award from Tesla, thanks Elon) and it has really transformed our consumption of grid supplied electricity more than I imagined it would.

As if writing this email, a few facts:

• It's a sunny morning in Melbourne and we are bring in a little over 3.5 kW (8:25am). If the sun keeps shining then we will be fully charged by 10:30am - 11am
• House is consuming 0.5 - 0.7 kW….house was using more kW around 6:30am as the AC started up to base load warm the house to 19C in habitable only rooms, trade off between what my wife wants of 22C and what I would like of 17C
• We have 2x Tesla’s…a Model 3 (changed from Model S previously) and a Model X. As a family we've been all electric since 2018, myself since late 2015
• We have a 12 kW system on single phase

Our house/habits:

• We use an Actron Platinum VSP system, ensure you are using this type AC of system if you want one of the biggest drawers of energy to be considerably less (VSP is the key, only Actron whom invented it and Daikin whom pays a royalty on it have VSP)
• House is North/East facing, single story, 80 year old weatherboard cottage with a 33% pitched roof in Malvern East. We stripped it inside and out about 5 years ago, doubled the size and packed it full of insulation etc. etc.)
• We have automatic blinds around the house, including a large outside balcony area, that controls light (radiant heat) to allow more in in winter and less in summer
• We charge the cars off of excess solar when we can (of course COVID has made this easier than I think it would normally be during winter)
• We have of course changed all lights to LED (including dimmable chandeliers, those bulbs are expensive, well the nice looking bulbs that is)
• We only run the dishwasher etc. during the day
• My wife is an amazing cook and the ovens (yes 2x of them), the commercial exhaust fan (yep, that's a power hog) and a small fridge (sounds silly but it makes a difference, we shop often) etc. all get a working out often when the sun isn't shinning

Given all of the above I am amazed we have been virtual off-grid (in terms of power draw) all winter.

We have been 99% off grid today and the past week, 92% for past month and 91% for lifetime (we only got the battery at the start of autumn)

My advice, pack out the roof with as many panels as possible (go 2x PW2's if getting a 12 kW system and you have the budget), continue to do as you say and insulate etc., get as power efficient appliances as possible,.

Note
Look at using a Hebel Floor on the first floor if possible, not sure which stage of building you're up to? It will make a considerable difference on a two storey house (heat transfer etc).

EDIT: Oh, and of course make sure you use Tier 1 Panels installed from a reputable installer...pm me if you want to know whom I used. They specialise in heritage types of homes where the "look" is a considerable road block when it comes to our "better" halve bosses.....

 

[ICUDoc]

Had a PW2 for a few years- works well.
It is NOT by any means a money-saver, though. It lets you get the most out of your solar .
(And got us through a THREE DAY blackout last summer. That alone was worth at least a grand to me....)

 

[paulp]

I think it is unlikley that 12kw of solar will be effective for 3 powerwall. You wont get complete fill very often, although it depends on your lifestyle. 2 is likley about right.
Make sure you have space next to your meter board for the powerwalls and gateway.

 

[paulp]

Dear Tesla Brains trust,

I’m building a house at the moment, looking to stuff as many solar panels as I can on to it. Expecting 10-12 kW size. The house will be large (5 bed), double storey, but I have also similarly stuffed as much insulation, double glazing, passive heating/cooling as I can into it as well. Three phase has been connected already + appropriate electrical wiring/switch gear is in the plans for similar.

I’m expecting to start making decisions on a battery for installation in say May or June 2021 and am looking at a Powerwall 2 (or 3 by then?). We’d consider 2 banks if it made sense.

Being in Melbourne, had anyone got a PW2 installed and can give some advice on things to consider for a rank novice? At the moment, we have one M3, but may be expanding to include an MY in a few years time.

Thanks!

Double glazing isn’t always the best solution. It stops heat escaping your house but it also stops heat entering in winter. Nothing beats the tried and tested shaded summer glass (unshaded in winter) and heavy drapes to keep heat in.
You might also like to consider micro-invertors rather than a single invertor. It costs marginally more (sometimes) but is much more efficient and keeps ylur wiring at 240v. There is loads of rubbish on the net suggesting they are unreliable, but as a 10 year user I’ve never had a failure on an enphase unit.

 

[EcoCloudIT]

Thanks for the detailed explanation. It is a larger volume builder hence the difference in cost vs. specialist design - with the benefit of having some cash to spend on additionals.

We have also specified the ground floor with Hebel, but not the flooring, no option on that

Will PM separately, appreciate the help.

The first floor, not ground, with Hebel will also make a big difference....will look for your PM shortly.....

 

[ICUDoc]

I think it is unlikley that 12kw of solar will be effective for 3 powerwall. You wont get complete fill very often, although it depends on your lifestyle. 2 is likley about right.
Make sure you have space next to your meter board for the powerwalls and gateway.

Yeah, i think you need about 5.5kW solar / Powerwall at Sydney latitudes

 

[jamesgo]

Yeah, i think you need about 5.5kW solar / Powerwall at Sydney latitudes

Melbourne based, 2.5kw north 1.5kw west (yeah small roof and the solar panel tech has improved a lot over the years on a kw per panel output, I think ours are 250kw per panel and now they're like 370kw per panel).

So 4kw and yeah most of the year off the grid (admittedly this year is a bit different cause we're at home during peak winter instead of being on holidays overseas). As for car charging there is quite a bit of free charging around where I live (50kw fast DC and also 11kw AC) including at the supermarket, so no real need to charge much at home.

 

[moa999]

Also depends on what electricity rates you can get.

Unlikely these days, but some people have a feed-in tariff that's higher than an overnight controlled load tariff,
So financially better to send power to the grid during the day and draw from the grid at night.

Not that they are quite available in Aus yet, but assume a volume builder also wouldn't let you install the Tesla solar tiles.

 

[EcoCloudIT]

Gotta love it, rained half the day but still got to fully charged and 100% self powered (via PW2 and Solar).

 

[AndyEV]

Actually, good news on this: just checked and both the ground and first floor externals are actually Hebel.

Really enjoying reading the stories from people on this.

The first floor, not ground, with Hebel will also make a big difference....will look for your PM shortly.....

 

[EcoCloudIT]

Actually, good news on this: just checked and both the ground and first floor externals are actually Hebel.

Really enjoying reading the stories from people on this.

@AndyEV - that's great, however I was referring to the first floor "floor".....just finished a house in Malvern East (French Provincial) with a Hebel floor....obviously one clads over the top of it (with board and timber/carpet) however it is just as good (thermally better) than a suspended concrete slab.

 

[lennier]

Gotta love it, rained half the day but still got to fully charged and 100% self powered (via PW2 and Solar).

View attachment 578534

That's doing pretty well. We get almost nothing from our 5kW array in this sort of weather! PW2 and ToU charging are still worth considering even in the absence of solar I think, depending on individual circumstances. We don't generate enough to be even close to off-grid (especially with car charging) but our peak grid consumption is almost nothing. Almost all our power usage even in winter is at super-off-peak rates which the PW2 automatically grabs overnight. Since that's cheaper than our FIT then no (economic) need to try to capture excess solar in the car.

 

[Wol747]

Double glazing isn’t always the best solution. It stops heat escaping your house but it also stops heat entering in winter. Nothing beats the tried and tested shaded summer glass (unshaded in winter) and heavy drapes to keep heat in.
You might also like to consider micro-invertors rather than a single invertor. It costs marginally more (sometimes) but is much more efficient and keeps ylur wiring at 240v. There is loads of rubbish on the net suggesting they are unreliable, but as a 10 year user I’ve never had a failure on an enphase unit.

We've had double glazing for over 45 years in various houses - with a deposited metal layer on the inside of the outer glass the heat DOES come in and is prevented from going out. The window acts as a large radiator.

Agreed on the microinverters - they make the best use of whatever each panel can produce, stop a single panel preventing any with shading reducing the output and they can be installed using various aspects making use of the sun all day.

 

[paulp]

We've had double glazing for over 45 years in various houses - with a deposited metal layer on the inside of the outer glass the heat DOES come in and is prevented from going out. The window acts as a large radiator.

Agreed on the microinverters - they make the best use of whatever each panel can produce, stop a single panel preventing any with shading reducing the output and they can be installed using various aspects making use of the sun all day.

There is no magic glass with a one way heat flow.
There is ample data to show heavy sealed drapes are more effective at keeping heat in than standard double glazing. I assumed being a volume builders house that the double glazing would be standard, or the cheapest possible. A higher quality IGU such as what you may have does start to outperform heavy drapes (marginally), although these are generally limited to high rise due to the cost, and as the quality improves so does The heat blockage, which is why you dont fry in the highrise office facing north with no glass protection. Unfortunately our building codes do not consider drapes which forces most down the double glazing route.
It gets even more interesting when you consider the new solar glass, which allows a diffused view out whilst making power. It reduces heat entry but you can make it up plus more from the solar power it generates.
My point is that the performance layer you have probably takes your IGU to better than drapes at heat retention, however that layer also blocks winter sun substantially but likely not completely. Once again ample data is available on that.
But a big asterix. Every part of Australia is different, which is why there are now expert consultants in this field.
Similarly most people think double glazing is best to keep noise out, when once again the data shows the same amount of glass as a laminated unit is a superior noise blocker.

 

[Vostok]

We use an Actron Platinum VSP system, ensure you are using this type AC of system if you want one of the biggest drawers of energy to be considerably less (VSP is the key, only Actron whom invented it and Daikin whom pays a royalty on it have VSP)

Do you mean Actron ESP Platinum? I couldn’t find VSP on the web...

Our house has a 12kW 4-zone ducted system (Daikin 3-phase non-inverter) as well as a separate 10kW 3-head multi-split system (Toshiba 1-phase inverter) to serve the rooms the ducted system cannot reach. The ducted system is 16 years old now and an absolute power-hog. No way we can run it just on solar or the PW2. The multi-split system is newer and much more efficient, we can easily run one of the heads purely on solar and PW2.

I have been contemplating whether we should upgrade the Daikin (although it’s still functional, and I generally hate replacing stuff that otherwise works), so I’m interested if you can tell me more about the Actron.

We replaced every window in the house early last year with double glazing, it made a massive difference to how often we need to use the AC. But this winter has felt colder than last, and with me working from home every day our power consumption has gone up a lot.

Totally agree with replacing lights with LEDs. Also agree with packing on as many high quality panels as possible. As panels get cheaper, the labour to install them becomes a larger component, so may as well max out the panels.

I went for optimizers rather than microinverters. It was a difficult call, but for our install, I went the optimizer route since I don’t want any failures - we had to scaffold the house to put the panels on. The optimizers we have are warranted to a higher temperature (85° vs 65°) and for 25 years instead of 10. The slight loss in efficiency to me is worth it if I never have to scaffold the house again.

Inverters and microinverters don’t have a great reputation for reliability. Even though our main inverter is a very well known Tier-1 brand, it failed only a few weeks after installation and had to be replaced. So given that experience, I feel like I made the right choice.

 

[Vostok]

Also depends on what electricity rates you can get. Unlikely these days, but some people have a feed-in tariff that's higher than an overnight controlled load tariff, So financially better to send power to the grid during the day and draw from the grid at night.

I’m on a plan with 21c FIT but off-peak tariff of 14c. Add in GreenPower charges of 2.8c and I’m still in front.

I’ve put my PW2 back into Time-Based Control, Cost-Optimising, and it seems to be doing a much better job this time around (newer software?). I’m WFH and using a lot more power compared to last year so a bit more cost-conscious. TBC-CO always seeks to charge the battery either from solar or the grid so that the battery is full just before the peak tariff starts. And when one is paying 55c peak tariff plus GreenPower, that’s quite a big deal.

Also the battery is charged at offpeak rates overnight if the forecast is not looking flash the next day. Over the past few weeks, that has really maximised our ability to go through the peak period purely on battery.

TBC-CO will reduce one’s “Self-Powered” percentage, so I’ve kinda let go of that as a virtuous goal. With 100% GreenPower I’m not feeling guilty.