Goal: Net Zero - Companies Suggesting Widely Varying kW Systems

[sensij]

When viewed as an alternative investment, solar for OP may be pretty good.
Saving $150 per month = $1800 per year
A $24,000 system after tax credit = $16,800
$1,800/$16,800 = 10.7% tax-free return.
If the money were to be taken from equities investments, at 25% income tax bracket, they would have to be earning 14.3% to equal.
The only downside is that solar is as illiquid an investment as the house itself.

Here is an alternate investment idea. Send me $10,000, and I'll mail you a check for $1000 each year. 10% tax free return, right?

There are some important financial concepts missing here.. compounding, return of principal vs investment return. I understand why the someone might be hesitant to move forward with this contract. How many people even live in the same house long enough to realize anything close to an acceptable return for tying up so much cash?

[brucet9]

Wow ... does solar make economic sense when the grid electricity price is so low? Of course if the Florida utilities are like the ones in California the price won't stay low for long.

When viewed as an alternative investment, solar for OP may be pretty good.
Saving $150 per month = $1800 per year
A $24,000 system after tax credit = $16,800
$1,800/$16,800 = 10.7% tax-free return.
If the money were to be taken from equities investments, at 25% income tax bracket, they would have to be earning 14.3% to equal.
The only downside is that solar is as illiquid an investment as the house itself.

[brucet9]

"What I've found strange is that after supplying my power bills, and last 12 months of energy usage, the various solar companies have given me a wide range of suggested builds - anywhere from 8.3 kW to 9.7 kW."

Nethers, I would suggest a little adjustment to your deliberations before deciding which proposal to accept. The nameplate power rating of all panels comes from a test called STC, done at the factory under controlled conditions with just a flash of light, basically for binning of the panels after manufacture. Unfortunately, the STC rated power is never delivered in the real world because of a variety of factors, including:
- Light induce permanent degradation (LID) occurring in the first few days of actual operation permanently reduces output of panels from 0.5% to as much as 5%, depending on the quality of the silicon cells.
- Temperature degradation is temporary, but in Florida will almost always be in play. Panels lose anywhere from 0.25% to 0.8% of power per degree C above 25 degrees (77degF) and panels generally run 20degC above ambient air temp. You will find this in the spec sheets under "temperature coefficient Pmax".
- Annual permanent degradation occurs with all panels, anywhere from 0.26% to 1% per annum is common.

I have noticed that the solar companies - all well regarded locally - that have proposed systems to me use STC values because it is easy, I guess, and they don't seem to take the other important factors into account in calculating output. It could be that some of your proposals do in fact calculate these known losses and have proposed larger systems in order to get your desired production.

Use the PTC wattage rating (it may not be in the spec sheet, but I have found that I can google it for panels I am interested in). PTC is a quasi-real world rating under load, generating power with 1kW/sq meter of sunlight at 68degF ambient temperature at rooftop height with a light breeze. It is a quick way to see which panels lose power from heat generated in use, albeit a little understated for FL where year round average temps are probably higher than 68.

Then check out the spec sheets on the proposed panels for light induced degradation (or google LID for those panels) and deduct the percentage of LID loss from the PTC rated watts. Now multiply by the number of panels proposed. This way you can better compare the power output for each of the proposed systems and the weaker performers should be revealed.

Then look at the "warranted [power] tolerance" on the spec sheet. The best panels will be +5%/-0% or maybe even +10%/-0%, meaning that the panels will deliver at least rated power and as much as the +%more. Lesser quality panels will be rated something like +3%/-3%, meaning that you could get as much as 3% less than rated power out of your system. With 28 to 32 panels in your system, you could safely apply the average of power tolerance figures to adjust output up or down to compare the various brands on an equal footing.

Finally, apply the annual degradation rate into the mix. Multiply that rate by 10 to see power loss in 10 years, by 25 for 25 years. Many companies show cumulative loss in a performance warranty chart on the spec sheet, showing anywhere from 80% to 90% production rate after 25 years. An inexpensive system that loses efficiency rapidly may provide less overall value than a more expensive one that retains its efficiency, sometimes in as little as ten years.

Once you figure out the best panels, look for another reputable dealer for that product and compare his proposed solution and pricing.

[max2k]

When we moved to SoCal we decided to put in solar ASAP. We were going to add a pool and but when I estimated the power cost of the pool it was so high I didn't want to put in a pool. Wife suggested solar. Since we had no history of use, I put in the most solar SoCal Edison would allow which was 2 times the square footage of the house. The first year before we had the pool, we produced a lot more electricity than we consumed. Edison sent us a $400 check for the excess power, which worked out to about 4.5 cents/kWh. We just finished the 3rd Relevant Period of our Net Metering Agreement. The Relevant Period is the year from the startup date of your panels. This time Edison sent a check for almost $100 for the excess power, which was at 6.5 cents/kWh. I have a spreadsheet to track my monthly consumption and exports. My total Edison electricity bills added up to -$28 last year. Yes, Edison sent me more money than I sent them. I have tracked what would have been my power bills each month without solar and my annual electrical cost would have been $3,450. My solar panels saved me about $3,480 last year. There were two months (December & January) where I imported more electricity than I produced. My panels cost $39,513 and after the tax credit the net cost was $27,659. That is about an 8 year payback or about 9% interest on my solar panels. The 9% does not consider the cost of capital, but since I'm getting about 1% on my cash, OK, call it an 8% ROR on the panels. I look at it like a tax free bond investment paying 8% which is right up there with one of my best, almost risk free, investments. Now wife wants a Tesla 3, so the larger load will eliminate my excess power generation over the year. This worked for me because of the climate and utility rates. The climate is sunny with moderate temperatures. I would call my system pretty close to net zero electricity cost. I would have had a higher ROR by installing a smaller system, but missed the downside of long term performance decline or the opportunity for extra capacity for a Tesla.

It's good to see happy case once in a while . If you don't mind me asking- could you provide few more details: size of your system in kW and your annual electricity consumption in kWh? It's hard to appreciate the deal without knowing few essential details. It sounds though you missed (this is easily fixable) the first most efficient way of savings on electricity- analyze and reduce your current consumption. Good news if EV is in the near future then you could utilize excess of power I'm sure you'll get from optimizing your current consumption.

[Ward L]

When we moved to SoCal we decided to put in solar ASAP. We were going to add a pool and but when I estimated the power cost of the pool it was so high I didn't want to put in a pool. Wife suggested solar. Since we had no history of use, I put in the most solar SoCal Edison would allow which was 2 times the square footage of the house. The first year before we had the pool, we produced a lot more electricity than we consumed. Edison sent us a $400 check for the excess power, which worked out to about 4.5 cents/kWh. We just finished the 3rd Relevant Period of our Net Metering Agreement. The Relevant Period is the year from the startup date of your panels. This time Edison sent a check for almost $100 for the excess power, which was at 6.5 cents/kWh. I have a spreadsheet to track my monthly consumption and exports. My total Edison electricity bills added up to -$28 last year. Yes, Edison sent me more money than I sent them. I have tracked what would have been my power bills each month without solar and my annual electrical cost would have been $3,450. My solar panels saved me about $3,480 last year. There were two months (December & January) where I imported more electricity than I produced. My panels cost $39,513 and after the tax credit the net cost was $27,659. That is about an 8 year payback or about 9% interest on my solar panels. The 9% does not consider the cost of capital, but since I'm getting about 1% on my cash, OK, call it an 8% ROR on the panels. I look at it like a tax free bond investment paying 8% which is right up there with one of my best, almost risk free, investments. Now wife wants a Tesla 3, so the larger load will eliminate my excess power generation over the year. This worked for me because of the climate and utility rates. The climate is sunny with moderate temperatures. I would call my system pretty close to net zero electricity cost. I would have had a higher ROR by installing a smaller system, but missed the downside of long term performance decline or the opportunity for extra capacity for a Tesla.

[organic farmer]

It is a balance.

Organic farmer gets to live in what he describes as paradise. Unfortunately the grid is not as complete there as in other States. But you have to weigh the advantages to the disadvantages.

I respect his decision to live where he lives and be happy with the lifestyle of an intermittent grid.

Thank you.

I served 20 years Active Duty on subs. For the last half of it, my biggest motivation was that we were going to build a homestead out in the woods after I retired [I hated living underwater]. After I retired we bought 150 acres and I built our house. Kind of re-invented myself as an organic farmer. We have been here 12 years so far. It has been a big learning curve. I am glad that I did this before I got so old that my body could not physically take it any more. I am in a couple Farmer's Markets, and we are pretty active with groups that help young farmers to get started.

The whole solar power thing goes along with the image well to keep it a complete package.

Solar power would never be economic sense if I lived in a suburb. We know a lot of people now though who live in townships where grid power has never been extended into. So it is their only option for power.

[SunEagle]

Some place you live ... Wouldn't be more cost efficient to fix grid issues? I mean if it's standalone house in the middle of some wilderness then may be but still- if there's power line it is connected somewhere if that somewhere has bad wiring / switch it would be much more standard exercise to fix that than to come up with reliable off the grid solution. If living off the grid is your hobby then costs are usually not a concern as fun component outweighs almost everything

It is a balance.

Organic farmer gets to live in what he describes as paradise. Unfortunately the grid is not as complete there as in other States. But you have to weigh the advantages to the disadvantages.

I respect his decision to live where he lives and be happy with the lifestyle of an intermittent grid.

[SunEagle]

Wow ... does solar make economic sense when the grid electricity price is so low? Of course if the Florida utilities are like the ones in California the price won't stay low for long.

It has been pretty low here in Florida for over 10 years. I can't say the same for CA rates.

[bcroe]

In this area 'net-zero' usually means a house that powers itself, heats / cools itself without consuming any outside energy. [no grid power, no fuel consumption].

A couple of extremely efficient "demo" houses have been built in the county, which require a minimum of
heat in the N ILL winters. But not net zero. With a solar grid tie here, an actual energy surplus was
created for far less $ investment, with a pretty average house. Bruce Roe

[max2k]

That depends on how many days each month you expect the grid to be available.

Here on the East Coast you should expect the grid to be up and functional 20 days of every month. Sometimes more, sometimes less.

The greatest asset of solar power is power when the grid is down, each month.

Some place you live ... Wouldn't be more cost efficient to fix grid issues? I mean if it's standalone house in the middle of some wilderness then may be but still- if there's power line it is connected somewhere if that somewhere has bad wiring / switch it would be much more standard exercise to fix that than to come up with reliable off the grid solution. If living off the grid is your hobby then costs are usually not a concern as fun component outweighs almost everything

[solardreamer]

Our 'Electrical Panel' is a 'Four Star Solar Power Center' from http://www.wholesalesolar.com

Thanks, good to know someone who actually bought from them. It looks like you have an off-grid system. I have looked at them before for their AC coupled offerings which are interesting but not cheap.

[solardreamer]

Our 'Electrical Panel' is a 'Four Star Solar Power Center' from http://www.wholesalesolar.com

Thanks, good to know someone who actually bought from Wholesale Solar. It looks like you have an off-grid system. I've looked at Wholesale Solar before for their AC coupled offerings (https://www.wholesalesolar.com/ac-coupling) which look interesting but they are not cheap.

[J.P.M.]

That depends on how many days each month you expect the grid to be available.

Here on the East Coast you should expect the grid to be up and functional 20 days of every month. Sometimes more, sometimes less.

The greatest asset of solar power is power when the grid is down, each month.

When I lived back east in central NYS, the last time the grid failed me for more than a few hours was in 1965 during the great northeast blackout.

You seem to live in an area that has unusually frequent and unusually long outages of the type most folks, for whatever reason, would not tolerate. I believe your situation is rather unusual.

My guess is most of the rest of the U.S. probably has better grid reliability than you do to the extent it's not a major consideration in PV system design.

[organic farmer]

What kind of grid-interactive inverter/charger battery backup system do you have? It was one of the original reasons for considering solar but soon found out utilities do not allow typical grid-tied solar system to be active when the grid is down. For my system, additional AC coupled inverter/charger battery backup system would be required to do that which does not make economic sense for my situation (very stable grid).

Our 'Electrical Panel' is a 'Four Star Solar Power Center' from http://www.wholesalesolar.com

[J.P.M.]

That's certainly true for each individual. What I was wondering is what rough percentage of solar owners decided to go solar even with low grid electricity price and for what economic reasons. I am guessing it's not a high percentage.

Follow the money.