Building an off grid tiny house on the Hilo side of Hawaii, Advice needed (new house, buy)

[hotzcatz]

Other than a catchy phrase, what does a Tesla powerwall do that a regular inverter & battery bank doesn't?

Last time we bought an inverter for the whole house it was about $1,500. Ten batteries at $80 each is $800, so an inverter/battery bank system is around $2,300 (although these numbers are from several years ago and currently the prices would be different, also depending on how many batteries and which inverter) and the Tesla is around $3,500.

[Irish Eyes_Mrs. Z]

Someone put out a cost estimate on that Powerwall/Solar roof. Here's the link, in case you didn't already see it:


https://www.youtube.com/watch?v=RjGwX0Pnn7A

I like the looks of the roofs. I don't understand the analysis, though--"maths" is not my area of expertise or interest. Thank dog for my husband. I wonder if it would be cost effective in Hawaii on the east side, where it's cooler and cloudier than the west side?

[hotzcatz]

Sorry, I'm not gonna listen to a ten minute video when one nice chart could give the same data. In any case, during the few minutes that I did watch, they didn't mention metal roofs, which is about the only roof option we have around here.

I'm sure Tesla makes a nice product, but folks building a tiny house are most likely going to be sensitive to installed costs, so unless it's a cost effective option, most small house folks will probably just use the traditional photovoltaic panels, charge controller, inverter & battery bank option. Better yet would be a grid tie PV system if they can get it. Then no need for batteries at all.

[TwoByFour]

Originally Posted by hotzcatz

Other than a catchy phrase, what does a Tesla powerwall do that a regular inverter & battery bank doesn't?

Last time we bought an inverter for the whole house it was about $1,500. Ten batteries at $80 each is $800, so an inverter/battery bank system is around $2,300 (although these numbers are from several years ago and currently the prices would be different, also depending on how many batteries and which inverter) and the Tesla is around $3,500.

Devil is in the details.

A traditional battery pack is lead-acid (LA). They are cheap to buy and is very well understood technology.

Lithium ion, which is what a Power Wall has in it, is new and is not really settled as far as PV systems. The Power Wall was first proposed using car lithium batteries but cars don't charge/discharge like a house does and it turns out the first Power Wall was a disaster for a house (fire danger). Tesla redesigned the Power Wall and now calls it the Power Wall 2 and that is what is being sold now. But it is still unknown how well it will work for houses because the reality is, there aren't many homes using it.

Cost:
LA batteries are down to about $100/KWH of energy storage. Lithium is about $400/KWH for storage for a non-Power Wall battery. Power Wall is hard to price because they won't sell it to a DYI homeowner - you have to buy it from a system integrator who will charge an installation charge + charges for special equipment because Power Wall is not compatible with most PV equipment (it operates at 300 Volts while most PV systems work at 48 Volts).

BUT, Lithium has a higher depth-of-discharge, which means you get more usable energy than you do from a LA battery. Plus, lithium lasts longer. You can charge/discharge it more times before it wears out.

Bottom line - I think Lithium ion will be the best battery in the future. I am not convinced that Tesla's Power Wall is quite there yet. There are competitive lithium ion batteries that are available now that work better but are more expensive. If you can get a good price on gel-cell batteries (a type of LA) I would get those now and upgrade to lithium ion in 5 years when your LA batteries wear out.

[edit] All this is moot if you are grid tied. Batteries are only needed for off-grid.

[MickeyE]

For starting places take a look at THE small HOUSE CATALOG® where they have over 40 free house plans. The plans may or may not be good for Hawaii, but it's a starting place. You can also purchase full plan sets and Sketchup models.

Mickey

[whtviper1]

Originally Posted by eddietude

There's a reason houses have a Lanai all around them... its so windows can be left open and rain won't come in.

Let me fix that for you.

There is a reason the roof extends over each of the walls in Hawaii - (although, that isn't terribly unique). Quite frankly, the architecture of single family homes in Hawaii isn't terribly unique.

Lanai all around the house - hmmmm, that probably makes up 1% of houses in Hawaii, at best - not much different than wrap around porches south of the Mason-Dixon line. On Oahu, I'd estimate just shy of 50% of single family homes have any lanai (porch for the mainlanders) with some quite nice and elaborate - some average to sit outside - and a bunch with a bunch of junk sitting on them much like the carport or garage space. Some are fortunate to have a upstairs lanai (balcony/porch) for the mainlanders but not exactly common.

[leilaniguy]

eddie, have you ever even been here?

[Jonah K]

Originally Posted by eddietude

I've perused a lot of real estate ads and most of them have a lanai all the way around, or at least around a chunk of the house.

Real estate agents in Hawaiʻi tend to use the term "lānai" rather loosely. Porches, patios, verandas, balconies, walkways, gazebos, sunrooms, decks, terraces, pergolas, and simple concrete slabs have all been marketed as "lānai."

[whtviper1]

Originally Posted by eddietude

Ok, then what is YOUR definition of a "lanai". I was under the impression it referred to all of the above you listed...

Well - no, not all that he listed.

From my perspective - a lanai is always covered by the roof - which many homes have and many do not. They would extremely be rare to surround the house as you mentioned. For mainland folks I'd describe it as a porch on the main floor and a balcony or deck on higher floors covered by the roof. They aren't unlike what you'd find all across the mainland but with a different term. They aren't terribly unique to Hawaii except the actual term they are called.

[Dreaming of Hawaii]

Originally Posted by eddietude

Ok, then what is YOUR definition of a "lanai". I was under the impression it referred to all of the above you listed...

The word lanai usually refers to a covered patio, porch, balcony, or veranda. It's usually a seating area attached to the house. I've never heard the following called lanai: walkway, gazebo or pergola.

I've seen some kits home plans sold here by HPM that have a wrap-around lanai, none of the 300 houses in my neighborhood have one.