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Cabin Permitting - Need sizing to meet Wa State energy efficiency Req

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Diemjoe

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Mar 18, 2021
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Hi,
I am trying to get a cabin build permit approved in Washington State. One of their requirements is to meet certain energy efficiency levels. I get 1pt towards the minimum of 3 for each 1200Kwh I generate per year. I avg 299 days of sun per year. Probably maxing 4 hours on 12/21 and 12hrs on 6/21.

How do I determine the number of panels I would need? I already have 2x 200w panels.

Thanks

Don Miller
 
They want you to generate 10kWh every day if I’m reading that right?!! To get a building permit? I assume that’s gridtie?

So running with the 4-hour insolation and figure making up a lot in summer and your 300 clear days/yr a wildhat guess would be 2500W of panels. But that’s guessing not using math. Or at least not using math much… and that only works for yearly averages.
 
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12VoltInstalls said:
They want you to generate 10kWh every day if I’m reading that right?!! To get a building permit? I assume that’s gridtie?

So running with the 4-hour insolation and figure making up a lot in summer and your 300 clear days/yr a wildhat guess would be 2500W of panels. But that’s guessing not using math. Or at least not using math much… and that only works for yearly averages.
Click to expand...

That's only if the inspector accepts the math on paper. In reality out there, Oct - Feb are completely pointless in most places for getting solar to be worth anything.

That's still not that bad though, if you assume they're working with 4 hours per day and 10,000w/day that's 10Kw/4=250Kw/hr which is 10 250w panels or the equivalent of. Since the only way to wire that up evenly would be an insane 10s or 5s/2p you might as well go with 12 panels to give you more wiring flexibility.

I'm assuming you're trying to get a grid tie system together? It'd probably be easier to go with straight grid and then add in the solar later. That makes the permitting much easier.

If it's completely off-grid, you shouldn't need any kind of permit or inspection. Where are you putting this?
 
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So they will not give you permit if you produce less than what they want you to produce? What if you are not the type that waste energy, the building is well insulated, etc.? I thought they want energy efficiency so why forcing some one they make more energy than what you need if it is about energy efficiency? May be I am reading it wrong.
 
12VoltInstalls said:
They want you to generate 10kWh every day if I’m reading that right?!! To get a building permit? I assume that’s gridtie?

So running with the 4-hour insolation and figure making up a lot in summer and your 300 clear days/yr a wildhat guess would be 2500W of panels. But that’s guessing not using math. Or at least not using math much… and that only works for yearly averages.
Click to expand...
 
12VoltInstalls said:
They want you to generate 10kWh every day if I’m reading that right?!! To get a building permit? I assume that’s gridtie?

So running with the 4-hour insolation and figure making up a lot in summer and your 300 clear days/yr a wildhat guess would be 2500W of panels. But that’s guessing not using math. Or at least not using math much… and that only works for yearly averages.
Click to expand...
My reading is that it is 10KWh / month. I am going to call over there today to confirm. Totally off-grid.
 
Bud Martin said:
So they will not give you permit if you produce less than what they want you to produce? What if you are not the type that waste energy, the building is well insulated, etc.? I thought they want energy efficiency so why forcing some one they make more energy than what you need if it is about energy efficiency? May be I am reading it wrong.
Click to expand...
This is a totally off-grid house. I do not know why they care so much if I am comfortable or not but then again I am right next to Seattle's King County so I think the creep is starting. My reading is that it is 10KWh / month. I am going to call over there today to confirm.
 
A couple of links in my signature block.

The first is the solar calculator and you can play with the numbers to hit the amount of panels you need, and will be real close to actual production. This includes weather data, so that’s why in the summer months some areas produce less.

The second is a post for Sizing a system in the Seattle area where you are in versus the Tucson area where I am at. The Seattle area needs so much more power.

My guess is to produce 1.2 real Mw of power annually, you will need more than 2.5 kw of panel because of the rain and also the short days in the winter.

It seems with the new proposed monthly fee on solar panels in California and this point system you talk about in Washington, people may be driven away from installing solar.
 
12VoltInstalls said:
They are requiring you to install solar on a “totally off grid” structure?
That’s whacked out
Click to expand...

That makes sense. If it's getting inspected for habitation it has to have an "adequate supply of electricity" which means a utility drop or the equivalent off-grid generation capabilities.

10Kw/month is only 350Wh/day, which isn't jack squat... that's only a 100w panel for 4 hours.

Unless you're in Western WA which is 26.5 acres of 500w panels in Oct-Feb. :)
 
Rednecktek said:
That's only if the inspector accepts the math on paper. In reality out there, Oct - Feb are completely pointless in most places for getting solar to be worth anything.

That's still not that bad though, if you assume they're working with 4 hours per day and 10,000w/day that's 10Kw/4=250Kw/hr which is 10 250w panels or the equivalent of. Since the only way to wire that up evenly would be an insane 10s or 5s/2p you might as well go with 12 panels to give you more wiring flexibility.

I'm assuming you're trying to get a grid tie system together? It'd probably be easier to go with straight grid and then add in the solar later. That makes the permitting much easier.

If it's completely off-grid, you shouldn't need any kind of permit or inspection. Where are you putting this?
Click to expand...
This is totally off-grid and it is at least a mile from the nearest utility pole. Way beyond my budget or interest to get on grid. I am in the county next to Seattle's King County and the escapees are moving over crushing the building department. They have had to outsource the review process to a Seattle Company and they are more strict. I had all this ok'd with a handshake last fall but now have to ramp back up.

I have been living there for 3 years (outside of winter) with 4 south facing 100 watt panels. It tough and I am very conservative with my electric usage.
 
Diemjoe said:
One of their requirements is to meet certain energy efficiency levels
Click to expand...
Adding offgrid solar or having no electricity at all is the same efficiency imho
Diemjoe said:
have been living there for 3 years (outside of winter) with 4 south facing 100 watt panels. It tough
Click to expand...
What charge controller?
Facing two panels SE and two SW was a big improvement for me, as was going to 800W total, again facing two directions.
Adding 400W isn’t terrible expensive.

Find out what you’re supposed to do and for what period and then you can go from there.
 
Rednecktek said:
That makes sense. If it's getting inspected for habitation it has to have an "adequate supply of electricity" which means a utility drop or the equivalent off-grid generation capabilities.

10Kw/month is only 350Wh/day, which isn't jack squat... that's only a 100w panel for 4 hours.

Unless you're in Western WA which is 26.5 acres of 500w panels in Oct-Feb. :)
Click to expand...
I am off the mountain for the winter. With the covid restrictions , I am hunkered down in small AirBnBs in middle of nowhere Montana. Plenty of time to think through this stuff. Permit philosophy where structural integrity is important for safety and any poor rescue workers who may need to rely on it when things go wrong. On the other hand, energy stuff, that is more of a comfort thing and shouldn't be any of their business. It is only 500 sq ft after all. I wasn't even going to build but because I pumped a water well, I cant pump it legally until I have a building permit due to water availability in the county. So this is going to be one of the most expensive pump houses ever built.
 
Diemjoe said:
I wasn't even going to build but because I pumped a water well, I cant pump it legally until I have a building permit due to water availability in the county. So this is going to be one of the most expensive pump houses ever built.
Click to expand...
What I did for my camp to get on grid and signed off was just provide power to the pump house. Once you're signed off and have your building permit code allows you to do rewiring of the house on your own... like say... for example... my 315ft 240v split phase backbone to the cabin... that "isn't connected" when the inspector shows up...

In short, don't tell them! :) Worked for me!
 
12VoltInstalls said:
Adding offgrid solar or having no electricity at all is the same efficiency imho

What charge controller?
Facing two panels SE and two SW was a big improvement for me, as was going to 800W total, again facing two directions.
Adding 400W isn’t terrible expensive.

Find out what you’re supposed to do and for what period and then you can go from there.
Click to expand...
I have a varied set up. A small 12*16 shed that I use for storage in winter. I uses it practice my building skills, try out design ideas and test building materials before I start the cabin build. That has 4 100 watt panels, an Mppt controller and an inverter. I don't recall the make of any of it but the Mppt is undersized for the 6 panels that I had originally. probably 20amp limit. I have 4 deep cycle .LA. batteries that are coming to end of life. I put a 23ft trailer on the property and have 2 200 panels charging its batteries. I did buy a couple 12v Lithium batteries from Big Battery and an all in one MPPT solar hoping to build out a 24v system. I learned after the fact that Big Battery doesn't support serial connection of their batteries. :-(
 
Rednecktek said:
What I did for my camp to get on grid and signed off was just provide power to the pump house. Once you're signed off and have your building permit code allows you to do rewiring of the house on your own..

In short, don't tell them! :) Worked for me!
Click to expand...
That was the original plan. But I can't get a well permit with out an approved residential permit. I just got the permit submitted in time to beat having to buy the permit again. They would refund the original cost but the new permit cost a couple hundred dollars more. With the way things are going out there, I don't want to risk losing the water rights if I don't get a proper residence up in time. I have 180 days from plan submittal to get my first inspection done or I have to jump through more hoops, checkbook in hand to keep moving ahead.
 
chrisski said:
A couple of links in my signature block.

The first is the solar calculator and you can play with the numbers to hit the amount of panels you need, and will be real close to actual production. This includes weather data, so that’s why in the summer months some areas produce less.

The second is a post for Sizing a system in the Seattle area where you are in versus the Tucson area where I am at. The Seattle area needs so much more power.

My guess is to produce 1.2 real Mw of power annually, you will need more than 2.5 kw of panel because of the rain and also the short days in the winter.

It seems with the new proposed monthly fee on solar panels in California and this point system you talk about in Washington, people may be driven away from installing solar.
Click to expand...
Thanks. I will dig in once the caffeine kicks in.
 
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