Proposal for solar panels on our garage

[Alan]

Quote:

Originally Posted by ERD50 Some opinion piece some where(it was a while ago) mentioned that if we are going to give subsidies for solar, it ought to at least be based on actual production, not installed capacity. That would eliminate some of this incentive to install as many watts as possible for the subsidy. -ERD50

This was the UK approach until they stopped the subsidy end of 2018. My neighbour installed his panels 8 years ago and it comes with with a 25 year contract to pay market price for every kWH generated, so he saves money by reducing his electric bills plus every 6 months he receives a form to complete and send in with the latest reading from his separate meter showing how much has been generated. (He gets about 12p/kWh currently)

[ERD50]

Quote:

Originally Posted by Alan This was the UK approach until they stopped the subsidy end of 2018. My neighbour installed his panels 8 years ago and it comes with with a 25 year contract to pay market price for every kWH generated, so he saves money by reducing his electric bills plus every 6 months he receives a form to complete and send in with the latest reading from his separate meter showing how much has been generated. (He gets about 12p/kWh currently)

Thanks, that's a much more sensible approach (though I don't actually think a subsidy in either form is a good idea). In the US, a person gets the subsidy based on the installed cost. A person in in a very good solar producing area, with their panels oriented at the optimum angles and an efficient, low cost installation charge might get a lower subsidy than one in a poor solar producing area, with their panels poorly oriented and maybe lots of shade that over-paid for the installation costs. If the goal is to promote reducing fossil fuel use, then the subsidy should be aligned with that. The subsidy actually rewards bad practices, an extrememly poor use of my tax $. Clearly, this is a very poor measure against the stated goal.

Even if one feels subsidies are a good idea to promote solar, they should rail against this "% of installed cost" approach, as it isn't really doing a good job of promoting the stated goal. A % of actual production does that better. The taxpayer would at least get more "bang for the buck", and the $ would go further towards the(questionable) goal.

-ERD50

[Markola]

OP here. Thanks for all of the informed comments, which make me glad we waited. OldShooter, Jerry1 and others mentioned the potential extra cost of replacing a roof due to hail, which would take away any savings, so that’s pretty compelling right there. All that said, the necessary trend of the world is toward electrifying everything and then decarbonizing that electricity. I expect massive innovation to continue and for the economics to improve.

To clarify two items from the discussion:

1). That $1,093 savings in the first year is just part of the subsidy. They pick up our first year’s worth of payments as a way to help bridge us to obtaining the tax credit in March or so when we file our 2021 returns, all with no out of pocket expenses.

2). I live in Minnesota and just changed my profile. Pardon the confusion. I must have been trying to be clever back when I first wandered into the forum.

[target2019]

If you have electric heat in MN, then it makes sense! I know MN gets a lot colder than NJ, and there is more spent on heat. In NJ we spend an average of $134 per month on natural gas. Some of that is a water heater. Our electric and natural gas bills are essentially the same amount. The major positive impact on natural gas cost was new HVAC systems.

If you're going electric vehicle, that tilts the decision a bit further in favor of solar.

For new construction I'd definitely take a swing at a solar installation.

[ERD50]

Quote:

Originally Posted by Markola ... All that said, the necessary trend of the world is toward electrifying everything and then decarbonizing that electricity. I expect massive innovation to continue and for the economics to improve. ...

I'll add to that (as I have many times in the past), if you want to promote solar energy to offset other forms of energy, you should be against residential installations.

The math and logic is simple. You want the most bang for the buck. Residential installs fail at all levels, compared to larger industrial/commercial installations). For residential, there is no economy of scale. Every site has to be analyzed, permitted, transfer switches installed, a crew has to get set up, and on to another place for each small installation. The roofs are steep and dangerous for the crew. The roofs are almost never at the optimal angles and/or free of shade (and future shade from growing trees). It's a stupid thing for the government to promote.

Put panels on a large flat roof (school, big box store, etc) and you have one crew working the same job for much longer, one site review, much safer working on flat roofs, easy to place at the proper angle and avoid shade. Residential in comparison is just wasting the valuable resource of the panels, which are very energy intensive to produce.

Quote:

Originally Posted by target2019 If you have electric heat in MN, then it makes sense! I know MN gets a lot colder than NJ, and there is more spent on heat. In NJ we spend an average of $134 per month on natural gas. Some of that is a water heater. Our electric and natural gas bills are essentially the same amount. The major positive impact on natural gas cost was new HVAC systems. If you're going electric vehicle, that tilts the decision a bit further in favor of solar. ...

I don't follow. What does consumption have to do with it (unless different cost tiers come into play)? You scale the system in line with your consumption (depending on your net-metering situation). It either pays for itself in X years or it doesn't.

It's like return on a fund - the % return is the same if you invest $1,000 or $10,000.

-ERD50

[Lsbcal]

Quote:

Originally Posted by ERD50 Yes, I've seen some of this as well. And an old thermal solar installation that was almost completely blocked by trees 10 years later. Some opinion piece some where(it was a while ago) mentioned that if we are going to give subsidies for solar, it ought to at least be based on actual production, not installed capacity. That would eliminate some of this incentive to install as many watts as possible for the subsidy. -ERD50

So there are no building codes and inspections for solar installations?

[Markola]

Quote:

Originally Posted by ERD50 Residential installs fail at all levels, compared to larger industrial/commercial installations). For residential, there is no economy of scale. Every site has to be analyzed, permitted, transfer switches installed, a crew has to get set up, and on to another place for each small installation. The roofs are steep and dangerous for the crew. The roofs are almost never at the optimal angles and/or free of shade (and future shade from growing trees). It's a stupid thing for the government to promote. Put panels on a large flat roof (school, big box store, etc) and you have one crew working the same job for much longer, one site review, much safer working on flat roofs, easy to place at the proper angle and avoid shade. Residential in comparison is just wasting the valuable resource of the panels, which are very energy intensive to produce.

That makes a ton of sense.

[ERD50]

Quote:

Originally Posted by Lsbcal So there are no building codes and inspections for solar installations?

I'm not sure what you are asking? More context please.

-ERD50

[Lsbcal]

How could someone mistake the location of a solar array? Shouldn't codes force a decent location away from trees and wrongly facing roofs? Shouldn't installers be required by codes to somewhat optimize an install?

[NW-Bound]

There are codes and inspections. However these only apply to safety issues. Each piece of equipment must be UL listed, for example. Wiring and grounding must be done to codes, etc...

It is hard to mandate certain orientation of the panels, or levels of shading by trees, or neighbor's roofs. Most of the orientations I have seen are suboptimal. How suboptimal is permissible? You will have to analyze the system output over a 12-month period, in order to cover all sun angles.

[ERD50]

Quote:

Originally Posted by Lsbcal How could someone mistake the location of a solar array? Shouldn't codes force a decent location away from trees and wrongly facing roofs? Shouldn't installers be required by codes to somewhat optimize an install?

What NW-Bound just said.

Also, there are a lot of shady (pun intended!) installers. As long as some clueless uninformed person is paying for (part of) it, the installer will put in the panels. If the installer says "hey, this panel will be shaded most of the day, doesn't make sense to add it", they lose the sale on that panel. But we, the taxpayer get to pay for some of it anyhow. It's ridiculous.

Happens a lot. Maybe not quite so egregious as that as often, but I'd say the vast majority of residential installs are producing less energy than the equivalent dollars invested in a commercial scale installation. It's a waste.

-ERD50

[OldShooter]

Quote:

Originally Posted by Lsbcal How could someone mistake the location of a solar array? Shouldn't codes force a decent location away from trees and wrongly facing roofs? Shouldn't installers be required by codes to somewhat optimize an install?

I can't speak to solar specifically, but the codes are not leaders. They are followers, attempting to keep up with new technologies* to maximize safety and construction quality. Hence, when new they are to a degree a guess. Then, as experience is gained, they are updated to reflect the new knowledge. I't bet that if you looked at the code relating to wooden house foundations, you'd see a decade or two of evolution from revision zero.

So maybe the codes "should" deal with location (I don't know) but it doesn't surprise me at all that maybe revision zero didn't.

*I have served on three national standards committees and have seen this first hand.

[NW-Bound]

And then, there are times you intentionally allow a certain level of shading in exchange for being able to mount more panels. Here's an example done in commercial installations.

Panels are mounted in rows, facing south, tilted to the sun ray, which of course is not vertical. The tilt angle is obviously a compromise, because the sun angle varies with the season. You may want to optimize it for overall annual production, or to maximize production for either summer or winter, while reducing the output at other times of the year.

And then, the rows of ground-mounted panels must have a certain spacing, in order to keep a row from shading the one behind it. If you space them at the correct distance far apart for the low angle of the winter, then you have fewer panels for the same area. What if you intentionally crowd them a bit closer than the optimal distance, knowing that you give up a bit at the early and late hours in the winter, at which time the panels don't get much light anyway? This allows you to mount more panels for the same area.

And then, there are panels specially made so that they don't lose a lot of output if they are partially shaded along the bottom edge in the early and late hours. I did not know about this type until I happened to see some surplus panels sold in the retail market. These are not intended for residential installations, obviously.

Commercial installations do a lot of optimizations, because they know what they are doing. Home owners usually know diddly-squat.

[NW-Bound]

It's good to know the OP is not in Alaska. Solar panels don't work too well there.

Even at summer solstice, when you have nearly 24-hour sunlight, the sun angle is very low, and worse, it runs around the horizon. You need to mount the panels on a tracker that turns 360 degrees in azimuth to chase the sun as it runs around you.

[finnski1]

Quote:

Originally Posted by NW-Bound First, chop down some trees and burn them for heat. Then, you have a clearing for your ground mounted solar array. Problem solved. I love ground mounted arrays. Wish I have a bigger lot than what I have right now. It's easier to build, easier to wire up, and to protect from strong wind, does not mess up the roof. What's not to like? PS. You may even be able to use the downed trees for lumber to build the mounting frame for your array. Beautiful.

Fair enough. But did I mention it is A LOT! of trees. Heck even to do a roof version I would still need to cut down quite a few trees. Living in southern NH isn't the ideal solar location but it would work reasonably well. The last 12 months my total usage was only 4080 kWh or 340/month with a low of 231 in May and a high of 575 in Aug. Last years annual bill was $889 or $74/month. I only get a reasonable payback period if I were to do the purchase and install myself. Because I am picky and a serious DIY 'er that is what I would do anyway

[NW-Bound]

PVWatts calculator at nrel.gov says that a standard 320W solar panel tilted up 45 deg will produce about 1 kWh/day in the winter, and 1.35 kWh/day in the summer, in Manchester, NH.

Just about 15 panels will get you all that you use. But of course that's on the average because there will be cloudy or snowy days when you get zilch.

I can get new panels in town for 15 x $150 = $2,250. You can now get a 6-kW inverter/charger along with a 13-kWh lithium battery for $6,100. The rest is lumber, wiring and miscellaneous hardware.


PS. Once you have the basic system, additional solar panels bring a very good marginal return for more kWhs, but you need to find ways to use the extra power during the day, else you will need more battery. For example, I run the pool pump during the day, and also the water heater. The water heater is turned off at night, and coasts until the morning.