Estimating future usage and system sizing

[sjsun]

CSI data came from applications for the CSI rebate. That rebate ended for residential customers in early 2014, before the 300 W LG panels were even released. No data has been collected since then. Most CSI prices are higher than what can be found today, as equipment prices have fallen somewhat since then.

D'oh! Thanks for pointing that out

I got two contractors to come down to $4.2/W installed. One's quoting 315W LG panel and the other has Hanwha 260W panels, a total of 17 panels. Both are including micro-inverters. Plus, $3500 for panel upgrade to 200Amp service.

[wrysys]

any other recommended installers in bay area, pls pm to me

[decaview]

Hi,

I live in the SF Bay Area (peninsula) and shopping for Solar. My current usage averages only about 500kW/month. So first, I am trying to estimate future usage. Right now, we are a young family (me, wife and a toddler) - that will likely grow and we are looking to add at least one EV in the near future and another depending on work/commute situation. For the first EV, I was eying the Mercedes B Class electric since it seems to be the only one with ample room for a small family. It is rated at 40kW/100 miles so with 1000-1200 miles a month of driving, the electricity usage would be ~500kW/month. Also, as kid(s) grow older, the current 500kW residential usage will climb up too. Maybe 700kW? In 3-4 years, with one EV, is 1000-1200kW/month a reasonable estimate of usage? (No pool, AirCon)

So far, I got quotes from Sungevity and Luminalt. Sungevity did not come out to the site yet and based on their remote survey, said maximum they can put up are 21 panels. For a 5.25kW system, they are quoting me ~21k before rebates/tax-incentives. Luminalt quoted me ~$25k for a 5.13kW system with Sunniva 270W panels (19 panels). They also quoted me $28k for a 6.2kW system with 23 panels (Luminalt did a physical site survey and said they can install 23 panels).

My questions are (1) Is my energy usage estimate reasonable? (2) If yes, then does it make sense to go for higher efficiency panels like the SunPower E20 or X21?

With a typical 250/270W panel, I can cover most of my residential usage (keeping me in Tier1 of the rate bands) with solar panels even if my usage goes up to 700/800kW/month.

But even though EV charging is only 10cents/kW right now (PG&E), it can go up depending on PG&E/CPUC policies where it becomes more expensive than Solar energy. At that point, I will pay a lot more to the utility than if I go for an over-sized system now.

Also, what is a rough method to calculate cost per kW generated? Assume 25 year life-span, estimate 1st year energy generation, adjust for panel degradation every year for 25 years and sum up the power generation over 25 years. And divide the total cost sunk into the system with the total power generated over the span of 25 years? (Not taking into account time value of money, inflation etc)

Would really appreciate either specific replies or in general, any replies explaining the larger context around which I should be making a decision.

Thanks

You got to do your meth carefully before investing in a solar system. With PG&E EVA Tariff, you may only need 2.5kw system to cover most of your bill. I just got a quote for 2.5kw system for $9k pre-tax. It is estimated to produce about $75 worth of electricity per month base on EVA Tariff and I use about 600kwh per month and cost me $95 per month.

[sensij]

Thanks ver2go. I very eagerly downloaded the CSI data but oddly enough could not find any installs with my panel of choice - LG 300W Neon. Per Watt price also seems to be cheap at the lower end of panels, below 280W. Looks like volumes are still low on the higher efficiency panels? Interestingly, I found one installer that seems very frequent in the CSI data but not reviewed much on Yelp.

CSI data came from applications for the CSI rebate. That rebate ended for residential customers in early 2014, before the 300 W LG panels were even released. No data has been collected since then. Most CSI prices are higher than what can be found today, as equipment prices have fallen somewhat since then.

[sjsun]

What I did was download the entire CSI database. Then started narrowing down in Excel.

For example,
Start with filtering on the local countries. I elected CCC, Alameda, SF, San Mateo
Then selected Sunpowers, since that was what I was looking for.
Then kept playing with filter and finally added a column to do price per watt.

Asked for estimates from there. Of course even all the installers with less than $4/watt in CSI still ended up quoting me way above $4/watt.

I guess I'll have to see what happens after the next election.

Thanks ver2go. I very eagerly downloaded the CSI data but oddly enough could not find any installs with my panel of choice - LG 300W Neon. Per Watt price also seems to be cheap at the lower end of panels, below 280W. Looks like volumes are still low on the higher efficiency panels? Interestingly, I found one installer that seems very frequent in the CSI data but not reviewed much on Yelp.

[solar pete]

+1 on this. I can't get anyone south of $4.xx. Does flat roof add that much more? Some installers are claiming that.

Howdy ver2go,

Iam in Oz so we have different architecture, BUT yes flat roof are a pita, as a general they do add cost to the install. Sometimes we cant install on them depending how its been made.

[ver2go]

No idea about flat roof but looking at quotes I got in February, I can't seem to get anyone below $4.xx either. Have prices fallen significantly since then? Is there a reliable site which I can use as reference for equipment pricing and then workout labor estimates accordingly?

What I did was download the entire CSI database. Then started narrowing down in Excel.

For example,
Start with filtering on the local countries. I elected CCC, Alameda, SF, San Mateo
Then selected Sunpowers, since that was what I was looking for.
Then kept playing with filter and finally added a column to do price per watt.

Asked for estimates from there. Of course even all the installers with less than $4/watt in CSI still ended up quoting me way above $4/watt.

I guess I'll have to see what happens after the next election.

[sjsun]

+1 on this. I can't get anyone south of $4.xx. Does flat roof add that much more? Some installers are claiming that.

No idea about flat roof but looking at quotes I got in February, I can't seem to get anyone below $4.xx either. Have prices fallen significantly since then? Is there a reliable site which I can use as reference for equipment pricing and then workout labor estimates accordingly?

[ver2go]

Sorry, got busy with work, family and smaller home projects and frankly, after talking to a few installers I just got so confused that I let go. Can you please PM me the name of your installer? $3 per kW sounds good

+1 on this. I can't get anyone south of $4.xx. Does flat roof add that much more? Some installers are claiming that.

[sjsun]

I just finished the install of a 6kW system on the upper Peninsula near San Francisco Airport.

We are low electricity users (family of four, average 425 kWh per month), and for years I did not pursue solar because my calculated return on investment was way beyond 10 years.
Then two things happened: I got an EV (Nissan Leaf) and I found an organization installing Solar for well below $3 per kW, which is far below what competitors quote.
Including cost of service upgrade (new main electric panel) and considering savings by replacing one ICE-car with the EV I calculate now an ROI within 6-7 years.

Sorry, got busy with work, family and smaller home projects and frankly, after talking to a few installers I just got so confused that I let go. Can you please PM me the name of your installer? $3 per kW sounds good

[Mike90250]

re TOU plans, study the plans for your area, they generally are NOT favorable for solar, and you may want to consider a "remote control plan" for Load Shaving, where for a reduced rate, a PoCo controlled relay is attached to major appliances which can be disabled for a pre-defined time period [ 1 hour off, 2 hours on] in a power crisis.

[jonathan]

I've found this thread to be particularly helpful as I get started with the home solar process.

We're finally considering solar now that we completed a major remodel/addition of our home, and have a completely different electricity usage pattern. We've been in the house for only a few months now, consistently using about 550kwh/mo (as opposed to about 40 kwh/mo during construction when not living here), and have done everything we could to reduce our electricity consumption.

We're thinking we will realistically need to wait almost a full year before solar installation because our 12-month rolling average is materially affected by 8 months of 40kwh/mo usage.

Any suggestions on trying to do TOU analysis of usage? In our case we have very efficient appliances, exclusively LED lighting, and generally no heavy demand. Our HVAC heating, water heater, clothes dryer and stovetop are all natural gas, though our oven is electric. No A/C.

What I've found is that the majority of our daily usage is based upon our idle load being high. The bulk of this is our HVAC system and ERV runs a consistent % of every hour. That's a material portion of our 0.5-0.6kwh idle load.

Ultimately I think we'll consistently use about 550kwh/mo year-round, with 75% of that based upon our consistent, idle load. We're currently not on a PG&E TOU plan, but I imagine we'd benefit from TOU with solar.

Any suggestions on tools that can help me understand what typical TOU production would be like, and how that would compare to our usage?

[ver2go]

I sent you a PM with my email address for the info. Did that work?

No, it does not work. I can read the PM, it even lets me type a response, but when I try to send the PM the following message is received:

To be able to send PMs your post count must be 10 or greater.

You currently have 3 posts and you can send PMs to following users only:
Jason, Mike90250, Naptown, solar pete, russ

This is just as the owner / mods have set the board up. They must have their reasons. I personally find this board very unwelcoming, you even have to log in to watch a picture someone has posted.

[silversaver]

Jan 2014, I have generation credit of -130kWh credit to my account.

In Jan 2015, I have used about 184kWh from SCE and still 7 more days left before end of Jan statement.


Estimating a solar system size can be easy or it can be difficult. If you want to make every penny count by sizing a perfect system, that is very difficult task... On my past 3 yrs history, the electricity consumption were never the same by month or year. Some like to use TOU plan to perfectly sizing their system by getting a small system and maximizing the return base on TOU structure from POCO, but they never considering the TOU plan will change over time since POCO aren't stupid. For example, the TOU peak hours are 2 to 8pm now unlike what it used to be 10 to 6pm. You are getting less peak credit during solar production....etc.

I took the easy way by sizing the solar system to cover 100% of my usage before the EV kick in. The EV can easy bring you to tier 4 for any home. I get solar system to save money while enjoy comfort life style. A smaller system will only save me few thousands from start, but I'm loosing more money and pleasure in long run. I'm not going to tell wife or kid not to use any AC/heater between hours from 2 to 8pm just because I like to get higher credit to gain more kWh.... It is a free world, choose what ever you like.

[Alisobob]

solar50.JPG

I use aprox 11k KwH's annually, and sized my system at 6.4 KW.

As you can see, some days I over generate, and some days I over consume.

Solar is unpredictable.... it is what it is, depending on the weather.

I ended the month slightly ahead, to roll credits forward towards summer and A/C use.

Some say my system it too big for my needs, because its overproducing in Jan, a poor moth for solar performance.

......time will tell