looking into solar: my thoughts

[Git]

That is how I understand the solar battery backup. Basically involves a transfer switch and as I recall, I think they said there was a 30 amp limit on breakers. So even with solar batteries, you still couldn't run things like the main house AC. Whole house generator would be the way to go if your thinking about extended outages

I would be looking at something like this from Costco - cheaper than batteries and extended run times on natural gas

 

[Git]

The battery wall makes sense as a cost savings option in certain geographies where the cost of power varies throughout the day. IE - you can store power when cheap and use it when expensive. I don't think many people fall into this category and again, you're into a lot of house electrical re-engineering if your home already is up.

Time Shifting if you are on the Time of Use billing. For people who are not at home during the day, you bank (store) power that you did not use during normal working hours and when you get home after work which is basically the peak hours ($.41 per kWh) you use the power from your batteries

One of the financial incentives in California for solar batteries is called SGIP - Self-Generation Incentive Program

From their website
Qualifying technologies include wind turbines, waste heat to power technologies, pressure reduction turbines, internal combustion engines, microturbines, gas turbines, fuel cells, and advanced energy storage systems

So the way they work solar batteries into that program, to qualify for their rebates, the battery system has to send "all its stored energy to the grid the equivalent of 52 times every year"

 

[Angelfire]

In had a Sunpower system installed last March. Grid-tie with 18 panels. I really only needed 16 panels but allowed for some headroom. I paid around $18k (cash) for the system so $1k per panel is pretty accurate (325W panels). That being said, this was my cost before my tax breaks. I would absolutely get multiple quotes. Some of these installers are busy so will purposely mark things up as they may not "need" your business.

Overall, we have been very happy with it.
Cheers.

 

[dcg9381]

rewiring should be relatively the same as adding a transfer switch for a generator, not extensive re-engineering.

It's not the same, as mentioned above, because the batteries have very limited amp capacity. Off the top of my head, 240V@30A is the max you "pull" from a Tesla battery, so basically you got to select individual circuit(s) to protect.

Yes, a generator will probably be a bit cheaper in the installation, but then you will have fuel costs. And depending how long the outages are (I've heard they can be multiple days) you need to plan to store a lot of fuel. Adding a large propane tank can be expensive if you aren't using it often. If you have access to cheap natural gas, then that is probably the best option.

Not only the installation, but $ per KW capacity. You can get a 20KW generator (standby, consumer grade) for under $6k (needs install). A propane tank here is about $1200 for 250-500 gallons (installed). Natural gas would be better. Fuel costs are nominal in a situation where you want the backup power.

A battery won't last days - probably just hours, depending on draw. So it might be great for brownouts in CA, assuming you don't need to run AC, but it's not an extended outage solution.

 

[tyme2par4]

A battery won't last days - probably just hours, depending on draw. So it might be great for brownouts in CA, assuming you don't need to run AC, but it's not an extended outage solution.

A battery absolutely will last for days if you also have solar.

 

[dcg9381]

A battery absolutely will last for days if you also have solar.

Highly variable. In my state, HVAC is required 24 hours day pretty much 8+ months out of the year. You'd need some big batteries to store enough power to run 4 tons of HVAC (2000 sqft home) from dusk till after sunrise...

I can see it in places like California where you're not running HVAC loads, maybe a refrigerator or two, and have a gas water heater.. Power requirements would be much less. But if you use less power, installing big batteries and big solar is less likely.

Powerwall 2 stores 13.5 KwH of power.
This would run a 20A HVAC system for about 3 hours of continuous use.

 

[Git]

Anyone thinking about having solar installed, it is pretty easy to run the numbers yourself using this website (it's a government website)

https://pvwatts.nrel.gov/

You start off by entering your location. If you want to add your actual address, it will pull up an overhead photo of your house and you can draw in the area that you want to use for solar panels

Based on what vavet mentioned, I threw in some number using Ashland VA, a south facing roof, roof mount, etc. Keep in mind the size of the system is DC kW, not AC kWh. For example, I have a 12.5 kW DC system that produces roughly 19,500 kWh AC annually. So for vavet I used 10 kWh DC which based on the weather modeling that website uses should produce about 14,000 kWh AC annually.

Then to determine how many panels you would need, divide that DC output of the system (10,000) by the rated output of the panel you are going to use (ie 320 watts) and you would come up with something like 31 panels. (If you have two different facing roofs you run each roof separately and then combine the totals). Keep in mind these are rough numbers, but you can narrow it down further and any good solar contractor will use something like aurosolar software to crunch the numbers. It's pretty common nowadays to even offer a 'performance guarante' that the system will produce X amount of kWh each year or they will make up the difference or upgrade the system to reach that goal

 

[99LeCouch]

Solar depends on the local electricity rates, their policy for net metering if any, what is done with excess generation, and incentives like rebates or tax credits.

We put a 3.5 kW system on in 2018. 10 LG 350 watt panels and a SolarEdge inverter. The cost was about $3 a watt before the incentives at the time. Not bad for the high-capacity LG panels.