OT: solar panels

[reuben]

I've read all I can handle from Ye Olde Internete, and a couple of Paceline threads on the subject as well. I'm looking for up to date info.

1. Northern hemisphere. Midatlantic US.
2. 2600 square foot house (oof! too big!).
3. Typical kWh/month is unknown since I've only been here for about 4 months. Looks like it may vary from 600 to 1500 kWh/month over the course of a year, but that's before...
4. I have other energy efficient things in the works - sealing the basement rim bands, adding insulation to the attic, etc., which will reduce the kWh/month, but probably not by more than 10%. Maybe 5%?
5. I'm looking at maybe ~12 kW system - TBD.
6. Panels (maybe Canadian Solar), inverter (maybe SolarEdge) - TBD.
7. I might cut down a couple of trees, but they provide shade to the back of the house in the afternoon, which would make a difference in the summer (more sun for the panels, countered by more heat onto/into the house), and no real difference in the winter (deciduous). Can't have everything, right?
8. Upfront cost might be $35k USD or thereabouts - TBD.
9. HVAC is geothermal.
10. 99% chance of going with net metering rather than a battery.
11. I'm looking to substantially reduce my electric bill, but not necessarily eliminate it.

As a (former) engineer, I've been collecting data during my short tenure here. It looks like I should keep my thermostat at a constant temperature in the winter, rather than lower it at night and raise it again in the morning. Raising it in the morning asks the system to do the most work at the coldest time of day during the winter, and that early morning spike would often exceed the kW generated by the solar panels. This works for my geothermal system. If you have oil, gas, propane, air source heat pump, or other, well... YMMV and all that.

I find all sorts of conflicting (and sometimes outright WRONG) information out there, so I figured I'd ask the most knowledgeable solar experts I've ever (not) known - Paceline cyclists.

Thoughts? Recommendations? The roofs (rooves?) are relatively shallow, 2:12, so I probably don't need to splurge on hydraulic disc brakes. Rim brakes should be fine.

[mdeth1313]

While not an expert, my understanding is if you're using geothermal (ground source), temp setbacks are not as big of an issue as the ground maintains a constant temp as opposed to the outside air temp.

[MikeD]

Why don't you get some quotes on a solar system rather than trying to figure it out yourself? I think they all use the program PVWatts to provide estimates. What you pay for power where you live is a factor (the more that is the better the argument is for solar and the shorter the payback period is). You've got net metering, which is an important consideration too. Geographical location (number of sunny days), orientation of your home (South facing roof is best), and shading from trees, chimney, etc. is a big factor too. Roof condition is a factor (don't put them on an old roof). My system is a 7.5 KW with Solar Edge optimizers. I generate more more power than I use over the year so, other than a small monthly bill, I don't pay for electricity. I have a/c and use it a lot in the summer, but have gas heat and hot water. I think batteries are a rip off unless you need them for emergency power. They like double the cost of the system and will have to be replaced at some point, well before the panels wear out. Anyway, you probably know all this stuff.

[reuben]

Originally Posted by MikeD

Why don't you get some quotes on a solar system rather than trying to figure it out yourself?

I did. So far they range from $35-75k USD for my cost, with production of 11-23kWh per year (23 kWh is way more than I need). While those gross numbers are comparable, when I try to dig down deeper their numbers don't lead to any sort of apples to apples comparison. And not all are forthcoming about the panels or inverters they plan to use.

I know the orientation of the house, trees, roof condition, etc.

[prototoast]

I am an economist, not an engineer, so I will say that you are missing a few pieces of puzzle to figure out what the financial return of this will be. How much is your monthly electric bill now? Does your electric company Do full net metering? How much do you get paid for extra generated electricity?

Unless you are baseline, electric bills are particularly high, the ROI on your solar panels seems considerably worse than where I've seen elsewhere.

[benb]

Not sure I can find it right now but I read an article recently that is something to watch for.

Apparently a whole bunch of the Solar companies that lease you panels are in major hot water due to not running their finances intelligently and now they are at risk of folding due to interest rate issues.

It's like they are extremely leveraged on all the panels they put on everyone's houses.. they wrote contracts to the homeowners but on the back end they have loans that increased rates.

If you're financing/buying them yourself this isn't an issue.

[Shane4XC]

Originally Posted by benb

Not sure I can find it right now but I read an article recently that is something to watch for.

Apparently a whole bunch of the Solar companies that lease you panels are in major hot water due to not running their finances intelligently and now they are at risk of folding due to interest rate issues.

It's like they are extremely leveraged on all the panels they put on everyone's houses.. they wrote contracts to the homeowners but on the back end they have loans that increased rates.

If you're financing/buying them yourself this isn't an issue.

If they go under, what happens to the panels? Are the contracts voided and they’re ripped off the homes? That sounds awful.

[MikeD]

I'd get a few quotes and pick a reliable company that's been in business for a while and has a good reputation and probably does roofing too so they know not to screw up your roof in the process. My system was not trouble free (an inverter and an optimizer had to be replaced which were repaired under warranty). I guess my system is about 5 years or so old. In all three bids, I was told what type of system it was, etc.

[dustyrider]

It would take me so many years to pay back even federally subsidized solar panels that it’s basically a no start for me. I wish it were cheaper to be environmentally conscious but it seems so far out of reach. All I can add is to contact some local solar installers as many of them around here are happy to chat with you about all the nitty gritty.

[glepore]

I had a nominally 18kw system in Va and was very disappointed. Needed the kw in the winter (electric aux heat) and its grey here for our shortish winter. System was sized to do approx half my actual load, and never really seemed to make a financial dent.
And the tax credit? Great if you're working and pulling down 150k/year. Living on retirement income I've never been able to use more than $500/annually and have 11k of 12.5 remaining, and I'm out of the house and into a new property. It carries over but is a joke.

[bigbill]

Many of my neighbors have had solar installed, which makes sense in NW Arizona. The power from the utility is mostly generated by wind and solar. Salesmen go door to door, with at least one a week knocking on my door right next to the no soliciting sign. The last guy was on a segway the whole time he was talking to me. His biggest selling point is all the money I'll make selling power back to the cooperative.

It's sunny here with very few cloudy days; it's the Mohave Desert, or Mojave, across the state line in California. The big non-starter for me is our snowbird status. We aren't here when it is really hot. Before we take off with the travel trailer and horse trailer, I set the thermostat at 82 degrees and all our windows have sunshade screens and heavy wooden blinds inside. While we're gone, the electric bill is <$80 a month. We have gas heat in the winter, so our winter electric bill is <$60. I don't think the payback would occur in my lifetime.

[rwsaunders]

The DOE is a good resource for financial modeling and for other links to making an assessment if solar makes sense for you. Imho, without the credits, it’s marginal and in many cases dependent on where you live.

We are working on a number of higher-ed projects where the 48C program essentially subsidizes alternative energy systems (solar, geothermal, EV stations, etc.) for non-profits, similar to a tax credit. Without the program, solar is a no-go, when you also take into account issues such as upsizing structural systems to address the additional load (3#/SF), upgrading to a reflective roofing membrane and upsizing the thickness of the membrane to match the life cycle of the panels (25 years). I.e, why install a panel system with a 25 year life cycle on a roof that needs to be replaced in 10 years?

FWIW, we are installing a 162MW system on an academic facility roof in Chicagoland and the panel system cost is $2/MW ($324,000) with an additional $100,000 to address the engineering, steel and roofing membrane upgrades, and modifications to the switchgear. ROI break even is 9 years taking into account the $127,000 rebate. System efficiency is 84% taking into account that the panels are bi-facial and the reflective factor of the white roof membrane improves the production level of the panels by 15%. Life cycle of the system is 25 years.

It’s a complex process to say the least, and the team consists of the MEP engineers, MEP contractors, CM, accountant and solar specialists.

https://www.energy.gov/eere/solar/ho...-photovoltaics

https://www.energy.gov/infrastructur...it-48c-program

[Ralph]

I would only put them on a new roof. And even then, I don't like things installed on my roof. How do you repair a leak. What happens when the flashing rusts out around chimneys and sky lights, and vents, and most of roof is still good. Who takes off solar panels to repair or replace roof. Here in Florida, many roofs don't last as long as the solar panels. If I could put them on a stand alongside the house, and I planned to live in house a long time, I would probably do it.

[jtakeda]

What answers are you lookin for specifically?
Solar design? KwH need? If cost makes sense?

Start with an energy audit to find out how much you use and think of things you can live without or replace with more energy efficient models.


I live completely off grid and recently replaced my entire set up. Not exactly an apples to apples comparison but I know how much stuff costs and I have a pretty good idea of what kind of draw each of my appliances has.

Also what kind of property do you have? Is there a place with good sun exposure you can install ground mount?

Does your roof need replacing? Thats usually a fantastic time to add solar.\

Just for reference I have a fairly well insulated house, with pretty poor solar exposure in the winter due to large towering redwoods.
My battery bank is 18kw and if I use energy at a normal rate that will last me about 5 days. Propane stove, propane fridge (for now), wood heat.

The fridge is your first place you should be looking if you want to reduce your energy consumption. Freezer on top model with standard doors (not french doors) has the best efficiency generally speaking

[old fat man]

We've been leasing solar panels since 2014. Wow, almost 10 yrs. $70 a month with zero up front. In 2023, we generated about 5000 kWh via solar and from what I can see on my electric bill, we've never exceeded 700 kWh used in a month. Usually we're under 400 I believe.

2800 sq ft house from 1938 in Connecticut. Central air added in 2022 and all appliances are 9 yrs old or younger. Primarily Oil heat with one ductless split used year round. Electric range and dryer. Four people all with electronics running frequently and I work from home full time.

What the heck are people doing that pulls 1200+ kWh a month???

I did the math and for 2023, we spent an average of $95 total on electricity which includes the fixed lease price. I think these panels paid for themselves right away because my bills before solar were always at least $100 and I didn't shell out anything for the panels up front.

Original lease was with Sungevity. They went bankrupt and sunrun bought/inherited my lease. Sunrun has been great for the most part. We had to move some of the wiring when we remodeled and they sent sunrun certified techs to do the work. They even forgot to bill me the $2k they had quoted.

Like another poster, I wish my system was larger since we added central AC and will probably add an ev or two within the next 5 yrs. I have ample, good southwest facing roof top available but I'd have to invest in a completely separate second system and that's not worthwhile for a 20-30% overall increase.

My lease ends in 2034. I will have the option to extend it, buy the panels outright, or tell sunrun to take the system off at their cost. There's no price set for extending the lease nor for a purchase price. I'm counting on the fact that a 20 yr old system is of no value to sunrun so they've got every incentive to leave it in place via sale or lease extension at a reasonable price. We'll see what happens in 10 more years.