ArizonaJon
Member
daniel, I have searched for a AC with soft start and could not find one. Only add on soft start devices. What brand of AC has soft start?
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Should I get 1, or 2 powerwalls for my existing PV system?
- Thread starter Jeff Hudson
- Start date
Pretty much every "inverter" type variable speed compressor is by definition a soft-start, because they ramp up the compressor on startup, so the startup peak draw is typically much less than the normal running currents. To my point of view an inverter style AC has many advantages over a soft start add on devices, chiefly far better energy efficiency.
All the best,
BG
jrweiss98020
Tessa's Tesla
Get what you can afford. You won't regret getting "too many". However, you might consider adding to the PV as well...
My A/C is a Bosch.
It looks like the "Inverter Ducted Packaged Unit" shown on this page:
Air-to-Air Heat Pump Systems | Heat Pump & Air Conditioning Systems | Products | Residential
Air-to-air heat pump systems from Bosch.
When I got my solar (ordered first thing after I bought my house, and installed a few months later) and learned that my solar+Powerwalls would not start it without help from the grid, I tried to get a soft-start device for it. I found several devices advertised, but I could not find anybody willing to install one. Electricians told me to ask an air-conditioner repair person, and the air-conditioner people told me to contact an electrician. Even when I promised I would not hold them responsible if the device damaged the A/C, nobody would install one. Apparently they're considered a kludge and not something a reputable professional wanted to mess with.
But when the old A/C died and was not repairable, all the A/C installers had units available that start slow and slowly increase. I still don't know (or care!) whether mine increases by steps or continuously. But the upshot is that it never draws the high starting amperage of the previous unit. I wasn't willing to throw out a working unit to get the soft-start. But I was happy to pay a premium for the soft-start once I had to buy a new unit.
So other than having to have Tesla come out twice, where does the huge pain come from? My son got solar and one powerwall 2 years ago and now that he has some more money, looking at getting a second. No doubt better to do all at once if possible.
ucmndd
Well-Known Member
Huge pain might be an exaggeration, but there’s a lot of duplicate work and complication.
For starters, for a long time Tesla wouldn’t sell a standalone powerwall at all. You had to buy them with solar. I think that might have changed at this point now that supply has improved, but I’m not sure.
Second variable has to do with utilities and AHJs - lots of variability here as well but in most places adding another PW means another permit, another interconnection application with the utility, etc etc. you can’t (legally) just bolt another battery to the wall and call it a day.
Matt-FL
Member
My local utility has a clause that if you change from solar only to solar + battery, you lose their grandfathered NEM status.
Other common reasons is Tesla may not service/install in your area anymore. All installers also seem to not want to touch anything else already there so if you follow a lot of posts here, other installers seem to not want to install anything more if stuff is already there. Cost is another factor. Like a lot of things, doing 1 PW means all the travel costs, full day pay, etc is still there and the installers have to weigh that profit vs. some other more profitable installs vs. 1 PW.
I'm a big believer in pay once, cry once vs. constant drip or death by 1000 cuts when it comes to solar projects.
two will likely not start larger systems even with soft start. I’m at 5.5 ton and soft start, can start, can’t stage up on a 12kva generator dedicated to the unit.
jgleigh
Member
Hopefully this gets better as solar/batteries become more common. Can you imagine an electrician refusing to touch your main electrical panel because they weren't the one who originally installed it?
Matt-FL
Member
I can vouch for living in an area Tesla no longer services. My project took 17 months from order date to install, most of that was Tesla fighting with my utility. Because of this, the Tesla employee installers (who were from Orlando) said my project was probably one of the last in my area. They now use a partner/contractor for Tesla installs, which increased the price 50% (if I compare my 2022 costs with today's Tesla.com/solar contractor quote).
Matt-FL
Member
That's where data collected prior to design can help tremendously. I bought a Sense and two Emporia Vue units to watch individual and combination usage amounts, to figure out top spikes and kWh needs. I found I was hitting 15kw spikes a few times a day, and went with 4 powerwalls to ensure I'd be covered with some additional future expansion.
Are you saying that you'd sit in your car with the A/C running if it got too hot in your house and the Powerwall was depleted? That sounds awfully unpleasant.
Another consideration for how many Powerwalls to buy is: What time of day is your power consumption?
I have two separate systems: One for my home which includes two Powerwalls, and one for the cottage I rent out, with fewer solar panels and just one Powerwall because the cottage is much smaller than the house, so it needs much less cooling. The lease I inherited when I bought the house required me to pay the first $100 of the renter's electric bill, so when I installed solar she had no incentive to conserve. Of course after that I put in that the renters paid their own electric bills. The next two renters, by using electricity during the day, and minimizing nighttime use, kept their electric bill to the monthly minimum. The current renters always go over the minimum, and have told me they don't care. Their bill is still a fraction of what it would be without solar.
My point is that if you need to use a lot of electricity at night when the solar panels are not producing, you need more Powerwalls. My Powerwalls are generally around 60% to 75% full when the sun comes up and starts producing. But when we get more than a couple of days of cloudy/stormy weather then I'm glad I have the added kWhs. It's not just what it takes to start your A/C. It's also how many kWhs you need to get you through the night or cloudy days.
Here's the thing that's bothering me and that I may not have expressed as well as I should have. I do not generate enough energy to operate off grid as I would like to (as many of those present here claim they do - no animosity or jealousy) and adding Powerwall's does not effect my deficient energy generation. The question in my mind that needs answering is what is the next criteria to help decide how many Powerwall's are optimal. I will candidly and happily answer any question or series of questions that helps me understand if a Powerwall solution is right for me. Okay, I'll get the ball started by describing my electrical utility customer relationship since the differences between my situation and anyone trying to help might struggle through without knowing all the details. My electricity utility provider does not generate the electricity I use as the customer. They purchase power from the TVA and charge me for the quantity of electricity I use and are regulated by the local utility commission. They charge me an access fee as well as the cost of the provided electricity which is based on what they were charged by TVA. This amount varies from month to month but it only varies by a slight amount. For what it's worth at the present time I am paying approximately $0.11/kWh. My solar PV system is connected to their side of the grid after first going through a separate meter that measures what I generate. This reimburse me for my generated electricity at the same rate they charge me for the electricity I use according to my consumption (let's call it that unless there is a better word) meter. They perform this calculation and charge me or credit me the difference. There are only two months (April and May) of the calendar year that I consistently generate slightly more electricity than I consume which results in a credit on the next billing period. It is my understanding that If I were to install a Powerwall that I would be exiting from our mutual contract, my Solar PV would be routed directly to the Powerwall and the generation meter would be removed. I think all of the forgoing description should give you a good picture of my situation. I envision that by adding a Powerwall and exiting my utility power purchase agreement will cost me a few dollars a month of inefficient usage but give me the ability to keep a few essential circuits powered during an outage. Oh! I think I am getting to the core of my lack of understanding. If I don't include my HVAC as an essential circuit then I will be more challenged to consume all that I generate. And to include my HVAC will require at least 2 Powerwall's. Okay, I think I've figured that out for now.
I'd like to ask another question that has no incorrect answer. Does anyone have any negative second thoughts about adding complexity to their electrical systems? I believe even if the Powerwall were to malfunction it would fail in such a way as to still allow the default electrical grid fully accessible. Is this the case? Another piece of information that may be relevant is that my situation requires a third party to install the Powerwall's. The good news here is that the same company that installed my Solar PV is Tesla authorized to perform the Powerwall installation.
It sounds like you have it figured out in the first paragraph.
Adding the Powerwall(s) in the second paragraph will give you backup power. Since many Powerwall installations allow the owner to easily bypass the Powerwalls for grid power, I don't really see a complexity downside. For backup, I would consider putting your AC circuit not on your Powerwall(s), and put the rest of the house on your Powerwalls, because you aren't a net exporter most of the year, and AC units use so much power that I think it might be a challenge to manage it.
Just my $0.02...
All the best,
BG
Thanks for the input. My situation is coming into focus. I have yet to initiate contact with the installer for a quote but your comment has me thinking about a variation on what you've suggested. What do you think about a subpanel leaving off my HVAC, have them slightly rewire my Solar PV to route half to a single Powerwall and the other half to the grid? Is this a possibility?
Electricity goes where there is a load. You don't route it. If your solar and Powerwall are connected, the electricity (power) will go where the load is. Once the home load is satisfied the rest goes to the Powerwall or the grid, or a combination thereof.
Off grid is the same, except by having a panel on the grid side of the gateway leaves those items unpowered. Solar power flows to the house and the Powerwall, and when the Powerwall is full the gateway will turn off (and later on) the solar to keep the solar power from frying the rest of the system.
Does that make sense?
All the best,
BG
Off grid is the same, except by having a panel on the grid side of the gateway leaves those items unpowered. Solar power flows to the house and the Powerwall, and when the Powerwall is full the gateway will turn off (and later on) the solar to keep the solar power from frying the rest of the system.
Does that make sense?
All the best,
BG
All I can say now is that I'm glad I'm not in your situation: As I understand it, you get some money back from the utility for your excess solar power generation but you have no backup in the event of a grid outage; but if you add a Powerwall for backup during outages, they will no longer pay you for excess power generation. So your dilemma is whether or not to give up the income AND spend money for the Powerwall in order to have some backup for outages. And to have A/C during failures, you'd need to spend even more to have more Powerwalls.
I never had the opportunity to sell my excess power to the utility, so I HAD to get Powerwalls for power during the night if I didn't want to run off the grid all night long. Also I have the highest grid electricity cost in the country but abundant sunshine.
Good luck, whatever you decide.
I never had the opportunity to sell my excess power to the utility, so I HAD to get Powerwalls for power during the night if I didn't want to run off the grid all night long. Also I have the highest grid electricity cost in the country but abundant sunshine.
Good luck, whatever you decide.
San Diego has surpassed Hawaii for a few years now. We're rocking $0.833 on-peak now (TOU-DR1) for probably the majority of folks without solar (>130% baseline which for folks without solar, is probably impossible to be under 130%, especially during the summer). I don't know what > 130% baseline is now, but it was about 400 kWh a few years back.
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