Tesla Solar Panels and Powerwalll

bcroe - thank you for your reply.

In answer to your queries, I was advised by a bat expert that 1kw of power was required.

You are right in that during the winter the bats are down nearby caves having a kip but in spring, summer and autumn, providing a roosting site may encourage not only existing bats but also more endangered species.

The bat expert advised that no residual power is required, i.e a large battery is not needed. When the system is not providing any power the space dues get cold but bats are pretty hardy creatures.

I am advised the bat box will be super insulated.

I imagine what I would like assistance on is a specification for something similar to that which might be fitted to a yacht. Can anyone assist?

Don’t you use electricity for heating with heat pumps? I doubt that a small generator would handle all of the heat pumps, unless they are manually staggered. My house in CT did not have electricity for 2 weeks after Sandy and most gas stations were closed for at least 10 days. I was fortunate that temperature in the house never dropped below freezing but surely it is not very comforting to wake up in the house when indoors temperature is close to 40F.

I am not surprised that Tesla has been promoting that idea since California is their larget market. With NEM 3.0 that is the reality for solar to have any reasonable payback.
In the past four years in California with two EVs I have come to the conclusion that I cannot breakeven without batteries. The changes in timing of TOU rates have eroded the benefits. Eight years ago I was able to shift so much consumption to off peak rates that I was a Net consumer of energy but I had a small credit balance and therefore no charge for the Net energy I consumed. Now, that rates have changed and with batteries I use my batteries to shift the loads out of the 4-9PM peak rate period. I also can generate during summer credits during peak and at September True Up I actually had 1000 kWhs of credit at peak rates. I am now on a NEM plan where I am charged Non Bypassable charges in addition to Minimum Delivery Charges so I charge my EVs and my pack during the day from excess solar. It all depends on where you are standing.
I was fortunate to be able to self install my hybrid inverter and DIY battery pack so the entire system cost me $11,000. Amortizing that cost over the expected life of 10 years and the expected amount of energy stored and used during that time will cost me $.20 per kWh which is still less expensive than the power I consume even at off peak rates. In the past five years I have not experienced a serious failure and the complexity is easy for me to deal with. Maintenance is not an issue with LFP. I understand my circumstances may be unique and I am fortunate to not be under the new NEM 3.0 which has incentivized battery storage for other new solar installs.. We do have four or five power outages a year and one lasted three days several years ago, so thare is that backup advantage which I have not allocated a cost to since the system has a very reasonable payback plus the peace of mind. I also use heat pumps in winter and they run for several months full time during winter and are easily handled by my system.

I don't expect to change your mind because your situation is different. I just want other readers to see that if their circumstances are like mine, batteries can make sense. I also understand that on this forum there are not that many members with a situation like mine, but I do understand that there are a number of lurkers that may find this interesting.

I certainly do use electricity for heat pumps. The Nuke plant is only a
short hike away, so about the worst outage in a couple decades was
when a car knocked down a pole on my line. This brick house does
hold temp for a while. But the original propane hot air system is still
here, not actually run for a decade. I do run the blower to fully utilize
my electronic air filter and to even out the house. The original thought
was for a very extended outage, my gen set could start now and then
for the furnace and well, as it was actually used at my previous place.

I did add a propane gen set, with 700 gallons sitting here on standby.
Never used. Bruce Roe

Yes, if you have multifaceted roof where mounting panels is difficult, then replacing entire roof with solar tiles is better option (but more expensive)

The structure is already built?

Scratch the bar heater, and an electrical battery.
Instead use the energy to heat a water tank, aka Thermal Battery. The water will act as a thermal battery, providing heat well into night.

At least 20 gallon at a guess.

If someone is skilled, they could build a heat pump water heater from a window AC unit (if not just buy one), far more efficient.


FOR the record, I do that with my hybrid water heater. It runs once a day in winter, hot water 24+ hours.
In summer it runs once every THREE days (its in attic, minimal heat loss then)
So, a Thermal Battery is very possible.

Its not so much the fire hazard (which is mainly due to build quality issue) but cycle life.
LiFeP04 can have thousands of use cycles, and if operated between 20~80% capacity is more than double that, some estimates of 50 years of useful life.

As noted earlier fire hazards from batteries is mainly a result of Lithium battery chemistry. Those chemistries containing Cobalt (NMC) have a greater risk of fire damage because that chemistry gives off oxygen when overheated. LiFeP04 (LFP) does not do that and also has less chance of overheating. I agree there are other fire risks from build quality issues including wires overheating, poor overcurrent protection and ineffective battery management processes.

Properly designed, built, and operated should not have that issue, but I agree and for sure "the best risk is no risk".
Besides LFP is cheaper.