Solar Question for Gurus

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Solar Question for Gurus

February 09, 2022, 12:30:43 pm

I have a solar related question for our Forum electrical gurus.

We are gonna have some solar sales people come by the next couple weeks to give us bids on putting in a PV system for our house. I don't want to get into all the various things involved with designing a home solar system. I want to keep this thread focused (if such a thing is possible) to one question, which I will get to eventually.

We keep our coach parked in our driveway whenever we are at home, which for the past almost 2 years has been most of the time. The coach is plugged into a 50A socket which is connected to our main house breaker panel. We have a Samsung fridge in the coach which is kept running all the time cuz we use it for extra food storage. We like to keep our coach interior temp in the range of 50-80 degrees all the time. This requires using the air conditioners (either one or both) in hot months, and multiple electric heaters in cold months.

I don't care to hear any comments on the wisdom of how we operate our coach when it is parked - it is what it is.

When temperatures are moderate (doesn't require heaters or A/C) I turn off shore power to the coach and let our solar panels maintain the batteries and power the fridge (through the inverter). Sadly, we don't get "moderate" temps in West TX much of the year. We usually have one day of Fall, and one day of Spring...otherwise it is Summer or Winter.

The solar salesmen will all want to know how much power we use in our house. This is like the very first question they ask. We have the past 12 months of electric bills, so it's easy to give them that number in kWh per year, or per month, or whatever. The problem is that having the coach plugged in distorts our power usage by inflating the number. In designing the solar system, I would like to shoot for producing around 100% of our average annual household consumption, or at least as close as we can afford. But I don't want to pay for the extra solar capacity needed to cover powering the coach.

So, my question - is there any easy way for me to figure out how much total power the coach is consuming on an annual basis? It varies so much from day to day and month to month... I have no idea how many days I run the A/C and how many days I run the heaters each year. We (on the Forum) have good numbers for the power consumption of the Samsung, thanks to Roger. I can add the fridge draw to the normal base line background power draw on our coach to come up with a kWh number for those two items. It's the air conditioning and heating that has me stumped, and of course they are the biggest power suckers.

Any ideas?

Re: Solar Question for Gurus

Reply #1 – February 09, 2022, 12:50:59 pm

Chuck, you can find out what the A/C's in the coach draw by looking at your meter and not powering the A/C's in the house and reading one hour of power on the meter. Then turn on the A/C's in the coach and see the difference for one hour for A/C coach usage. Then do the same with the heaters. Not perfect but the best I can come up with.
I don't think you can put up enough solar in your climate area to get 100% of your usage. I know I can't here in the San Fernando Valley and my winters don't need heat but summers really suck the power.

Re: Solar Question for Gurus

Reply #2 – February 09, 2022, 12:54:28 pm

Quote from: craneman – February 09, 2022, 12:50:59 pm

I don't think you can put up enough solar in your climate area to get 100% of your usage.

I'm sure you are correct. It's just something to look at (lust after) initially, and then scale back from there to a realistically affordable level.

Re: Solar Question for Gurus

Reply #3 – February 09, 2022, 01:21:21 pm

To build on Craneman's idea and using the meter formula I posted here:

50A outlet in the generator compartment?

You can time the meter disc for 1 revolution to get the watt usage and not have to run for an hour. For the tests measure the house baseline, then add each coach load, measure and subtract to find the difference. For example if the difference is 2000 watts with coach A/C on, then over an hour this would be 2 kWh. Then estimate how many hours the coach A/C is running each day on average and multiply by 30 to get your total monthly kWh usage, then x 12 for annual kWh usage.

Re: Solar Question for Gurus

Reply #4 – February 09, 2022, 01:34:46 pm

Thanks for the help, Chuck and Peter, but I just answered my own question. And slapped myself in the head.

Sometimes I am such a dumb a$$ I wonder how I've managed to live so long.

We've lived in our house for 40+ years and nothing significant has changed that would affect our electric usage. We've owned our coach since late 2013. All I need to do is go back in my files and dig out the paper utility bills for a couple years prior to our purchase. Total the monthly usage for 12 months and come up with a average monthly kWh before plugging in the coach. SIMPLE!

Re: Solar Question for Gurus

Reply #5 – February 09, 2022, 02:13:35 pm

We changed all the lighting in the U300 and the house to LEDs. All TVs LEDs. Can't save too much on wash/dry but our LG front loaders save water and are more efficient. Later dishwashers do also. We went to the top rated but inexpensive Bosch dishwasher and it does a great job on fairly clean dirty dishes in 30 minutes, dirtier dishes in a couple of hours and makes very little noise plus no electric rod but air blower. How about solar powered LED outside lighting including security lights? Low water usage toilets, shower heads, etc. How about a small storage tank? Could have a planter around it so not ugly. How old is your fridge? Older models can use the "green" https://www.envirogadget.com/energy-saving/savaplug-energy-saving-device-for-fridges-and-freezers/ Energy star appliances save energy also. You probably have a swamp cooler in W.Texas with your low humidity. Other ideas online.

Our coach inverters will supply the house but the batteries are 13 years old so I don't like to cycle them too much. We also have the transformer to convert to 220V for the well but I don't like to run the PowerTech too much.

We are a lot like West Texas with a short spring and short fall with lots of winter and one day after another of summer days of over 100. This winter has been the warmest on record and will get close to 80 in the Sierra foothills. Didn't even use the heater yesterday or last night.

Pierce

Re: Solar Question for Gurus

Reply #6 – February 09, 2022, 02:16:52 pm

Sounds like you have a good handle on it Chuck. Here in Vegas we have a similar weather pattern it seems...2 weeks of spring and fall, the rest is summer or winter.

One thing I'll mention as it pertains to power draw is about the A/C's. When it's 115 here in Vegas, I would set the coach for 90* and both A/C's would be running quite a bit. I knew this was a big draw and wear and tear on those older roof mount units. I picked up a 14k BTU portable A/C unit and put it right in the middle of the living room, and ran the exhaust out the passenger side small side window. This unit only pulls ~900 watts to make 14k BTU of cooling, which is more efficient and saves the wear and tear on my roof units. I set it to 84 or so, and let it do the bulk of the work. If it fails, it's under Lowes warranty for a few years, and at $450 new, it's about 1/4 the price to replace one of those roof units. Just a thought for you if you endure the same kind of temps.

The other thing I will mention, since I have also been working on my solar and talking to the battery manufacturer (Lifeline) recently...there is not only a lifetime rating on batteries, but also a "cycles" rating on them. On those days you are unplugging from shore power and letting the solar maintain the batteries, each day is a cycle as you are draining the batteries over night and charging them again from the solar the next day. If you left it plugged in to shore power, the minimal power needed to maintain the batteries in the float mode keeps from cycling the batteries, which may prolong their life.

Re: Solar Question for Gurus

Reply #7 – February 09, 2022, 02:30:34 pm

Maybe an expert on batteries will clarify this. I thought a cycle was from charged to discharged and a charge to half charge would only be a half cycle. And so on for less discharged.

Re: Solar Question for Gurus

Reply #8 – February 09, 2022, 02:36:07 pm

Quote from: Chuck & Jeannie – February 09, 2022, 01:34:46 pm

Thanks for the help, Chuck and Peter, but I just answered my own question. And slapped myself in the head.

Sometimes I am such a dumb a$$ I wonder how I've managed to live so long.

We've lived in our house for 40+ years and nothing significant has changed that would affect our electric usage. We've owned our coach since late 2013. All I need to do is go back in my files and dig out the paper utility bills for a couple years prior to our purchase. Total the monthly usage for 12 months and come up with a average monthly kWh before plugging in the coach. SIMPLE!

I would have to go to the landfill to find my utility bills from 2013

Re: Solar Question for Gurus

Reply #9 – February 09, 2022, 02:58:38 pm

Chuck,

Keep in mind early and late in the day and cloudy days will give you a lot less output. There isn't such a thing as too much solar - only the size of your wallet.
Jim

2002 U320 42'

1000 watts on the coach and wish I had more

Re: Solar Question for Gurus

Reply #10 – February 09, 2022, 03:18:41 pm

Lol I didn't want to say anything but that's hat I was thinking. Average utilities divided by years. I just googled average house hold usage per day for the US and it's 30kw. Just looked at my bill for last year and I'm double that.

Re: Solar Question for Gurus

Reply #11 – February 09, 2022, 03:44:14 pm

Chuck, we have about 12,000 watts of solar panels on our roof in a grid-tied system. (we sell excess power back into the grid, no storage component) Over the past 4 years, we have sold more power than we purchased. About 2 months' worth of consumption every year. This last year we were home most of the summer and it was unusually hot. I Ran AC for about 90 days vs a normal 12 days. We paid about $40 for the extra AC time.

Ask about micro inverters on each panel. Output is 220v AC. The cost is balanced against wiring, big DC to AC wall mounted inverters. Since installers like to match inverter size to production capacity, you can be left in a situation where adding panels gets very expensive because you need another big inverter. With micro inverters, you just connect them. The only size limit might be switches or circuit breakers.

MN is a very friendly solar power state. Not sure how it is in TX.

What your coach uses might be offset by what your house does not when you are away. And as you get older you will use more electricity for every reason you can think of. We were shooting for 120% of our annual use. It is probably low for us, someday the coach will be gone, we will be home more, MN is getting warmer, we are getting older.

If you can sell excess into the grid then set it up for that. If you have frequent power outages consider battery storage. It gets expensive, especially so, if you need a day or more of backup. I have 6 8Ds in my garage on a charger/inverter. Excess solar charge them, they would power refrain, freezer, some lights for maybe a day. Far longer than our longest outage in 20 years.

Do as much solar as you can. Maximize watts per sq ft. You will maybe want to put a new roof on before panels.

Re: Solar Question for Gurus

Reply #12 – February 09, 2022, 05:57:57 pm

Sorry - had to take a break and watch the DVR recording of the Olympics from last night. Trying to stay caught up.

(Reply #5) Pierce, good ideas on saving electricity. There's definitely some places we could do better. We're spoiled cuz power is fairly cheap where we are...at least for now. We pay 8.3 cents per kWh bottom line price after delivery and all taxes and fees. Our fridge is very old and due to retire. Swamp cooler? No, afraid not - we have a heat pump for A/C and heat. Because of the DW's allergies we keep the house closed up and the heat pump runs almost every day one way or another.

(Reply #6) Keith, novel idea on the window unit to cool the coach when parked. Never thought of that! Our Atwood roof A/C units are only about a year old so should have a lot of life left in them. I'm not too much concerned about cycling our AGM8D coach batteries cuz they are 8 years old and probably approaching end-of-life, but still work OK. Need to ponder if I want more AGMs or go lithium... Getting old - gotta look at how much longer we might be physically capable of traveling in our coach.

(Reply #8) Chuck, some (unkind) people might consider us hoarders. I have paper records going back to the early 70's when we got married. Ever once in while, it comes in handy for looking up some obscure date or fact...like now.

(Reply #9) Jim says "There isn't such a thing as too much solar - only the size of your wallet." Yes, mine (the wallet) keeps getting smaller every year.

(Reply #10) Eddie, yes, that's about where my numbers fell for the house + the coach - about 69 kW per day. Haven't added it up (yet) for time before we got the coach.

(Reply #11) Roger - I've been reading about the Enphase IQ8 micros, and their AC-coupled batteries. Sounds interesting, but pricey.

What You Need to Know About Solar Batteries and Energy Storage | Enphase

I am getting quotes on a ground based system. We just put a $20k new roof on our house last year, and I don't want them punching a bunch of holes in it. We have 2 acres of south facing unused property behind our house, and you may recall we had a 1/2 acre cleared a few months ago for the RV parking pad. I had in mind leaving adequate space for the solar racks when we did that...

Parts of TX are solar friendly (like Austin) and parts aren't (like Midland). I won't get any financial assistance on the local or state level, but at least the Federal 26% tax credit is still in effect. Don't know yet about selling back to our electric provider (Reliant). Need to check on that. We DO already have the fancy digital electric meter that communicates with the utility.

My first solar salesman (SunPro Solar) is coming out tomorrow. If the moderators don't mind leaving this thread open, I'll come back tomorrow and let you guys know what he says. I know many of you have lots of experience with solar, and I learn from every comment.

Re: Solar Question for Gurus

Reply #13 – February 09, 2022, 06:05:24 pm

Roger, What is your cost per kwh for solar? Is that figuring in your installation cost?

I was going to ask if you had figured that out but as I was typing I knew that was going to be a dumb question for me to ask.

Re: Solar Question for Gurus

Reply #14 – February 09, 2022, 06:15:14 pm

Great thread. I've been thinking about solar panels. Didn't know about the micro inverters. From what I have read they are way more efficient.

Re: Solar Question for Gurus

Reply #15 – February 09, 2022, 07:34:15 pm

Quote from: Chuck & Jeannie – February 09, 2022, 05:57:57 pm

(Reply #6) Keith, novel idea on the window unit to cool the coach when parked. Never thought of that! Our Atwood roof A/C units are only about a year old so should have a lot of life left in them. I'm not too much concerned about cycling our AGM8D coach batteries cuz they are 8 years old and probably approaching end-of-life, but still work OK. Need to ponder if I want more AGMs or go lithium... Getting old - gotta look at how much longer we might be physically capable of traveling in our coach.

Just to clarify, not a window unit, but a portable that exhausts out the small window. My coach has a small sliding window next to the passenger seat that's about 8" x 8" or so. The exhaust hose for the unit is 6" diameter so I use the window adapter that came with it, cut down to fit, then taped in place. I put it in when I'm not using the coach and just wheel it out when we get ready to go. This is the unit I bought (in white): Amazon.com: LG 10,000 BTU (DOE) / 14,000 BTU (ASHRAE) Smart Portable Air...

Quote from: Chuck & Jeannie – February 09, 2022, 05:57:57 pm

(Reply #5) Pierce, good ideas on saving electricity. There's definitely some places we could do better. We're spoiled cuz power is fairly cheap where we are...at least for now. We pay 8.3 cents per kWh bottom line price after delivery and all taxes and fees.

That's super cheap. I bet it will take you many years to recoup the cost of the solar when your electric is that cheap. I pay $11.9/kWh here in Vegas.

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Re: Solar Question for Gurus

Reply #16 – February 09, 2022, 08:07:18 pm

Quote from: WS6_Keith – February 09, 2022, 07:34:15 pm

Just to clarify, not a window unit, but a portable that exhausts out the small window.

OK, got it. I just misread your post. Still a novel idea!

Re: Solar Question for Gurus

Reply #17 – February 09, 2022, 08:20:30 pm

Quote from: WS6_Keith – February 09, 2022, 07:34:15 pm

That's super cheap. I bet it will take you many years to recoup the cost of the solar when your electric is that cheap. I pay $11.9/kWh here in Vegas.

Yes, we had a solar salesman from another company come by our house last year, when we were paying the same price for electricity. He ran the numbers and said he could not come up with any way, based solely on the economics, to justify the cost of his solar quote.

We put the project on a back burner at that time cuz we were planning to replace our roof.

I'm not worrying too much about trying to make the numbers work financially. I look at it more as a way to enjoy the benefits of power produced right in our backyard, and to reduce (not eliminate) our dependence on the electric providers and the grid. We have 2 more years on our electric contract, then will have to negotiate a new one. Who knows what we will have to pay next time?

I also look at it as a fun science experiment. Pretty much the same reason we put solar on the roof of our coach. I like to learn about new technology first hand, by actually using it. It will be entertaining to have solar, and hopefully will add some value to our house. I figure this is a good time to buy solar, before the 26% Federal tax credit goes away. No word yet on if it will be renewed.

We are in the fortunate position to be able to afford this kind of project without suffering any financial distress. I figure we might as well spend it on technological toys while we're still kickin' cuz you never know when your time will be up.

Re: Solar Question for Gurus

Reply #18 – February 09, 2022, 08:35:09 pm

They are cutting the discounts on solar here and the excuse is that all the people that went to solar cut the profit of the power company so they raised the price of electricity. So in effect the ones without solar are subsidizing the solar users. The ones that have contracts planned on the discounts to pay back for the installation in 10 years, now they say it won't pay back in their lifetime. Have to see what happens now.

Re: Solar Question for Gurus

Reply #19 – February 09, 2022, 08:49:38 pm

Best is to get off the grid entirely. California's PG&E is the nation's biggest utility but easily the worst. Anytime it's windy or have snow, we lose our utilities for days in a row. Three weeks is a long time and while we got just our power back after three days, many neighbors waited weeks in freezing temp, no phones or internet. Solar panels are super inexpensive and if you do it yourself, it's not that expensive and will pay for itself in a short time.

Pierce

Re: Solar Question for Gurus

Reply #20 – February 09, 2022, 09:22:33 pm

I considered putting solar on my roof well over 10 years ago,
With a full battery system to store the power, As in full off grid,
They did give a good deal back then for buying back the excess power, Its not like that now, They only give peanuts now,
Now, If the batterys had lasted this long, I would be up for a new battery bank,
Costing it all out over the years,,
It would have been just a total waste of money,

Its still cheaper by a long way to just use the grid for my power,

Re: Solar Question for Gurus

Reply #21 – February 09, 2022, 10:27:35 pm

I finished adding up the numbers for two 2-year periods from just before we purchased our coach. Those two years are a good representative of our actual energy usage. Nothing in our house has changed since then that would materially affect the amount of power we use in the house. We did buy our Chevy Bolt in 2019, but we don't drive it enough to make any difference in our electric bill.

SO, our "pre-coach" annual power draw was 21555 kWh, which is 1796 per month, or 60 per day (average).

After buying the coach, we used (last year) 24877 kWh, which is 2073 per month, or 69 per day (average).

Having the coach sitting in our driveway adds 9 kWh per day to our annual consumption, or roughly a 15% increase in our annual electric cost.

9 kWh per day at our delivered rate of 8.3 cents per kWh = $0.75 per day. That's actually a lot less extra cost than I imagined!

I know we use a lot of power for the size of our house. I think the biggest reason is that we like to keep the temperature inside at about 70 degrees all year round. That really works our air conditioner in the summer.

On the plus side, we are 100% electric, so we don't have any other utility bill, like water or gas or sewer. We are on a water well as our only water supply, and a septic tank for waste disposal.

Re: Solar Question for Gurus

Reply #22 – February 10, 2022, 01:23:49 am

We are 31/2 years into our house solar system, we were connected in august and we get our bill once a year in august. The first 2 years we were about 100 kw positive but this last cycle we were 102 kw in the hole. Our usage hadn't changed still frugal with the thermostat, 65 at night and maybe 70 during the day with the AC at 70. It turns out that the cooling cycle for the on demand hot water was the culprit, that had been installed earlier however our gas bill went down by over 65% so swings and roundabouts.
Our calculations at the time of installation of solar was with the rebates and the price of electric at the time break even would be less than 14 years. As an aside I do natter a little about the initial damage done manufacturing them but oh well.

Re: Solar Question for Gurus

Reply #23 – February 10, 2022, 07:16:43 am

"I am getting quotes on a ground based system. We just put a $20k new roof on our house last year, and I don't want them punching a bunch of holes in it. We have 2 acres of south facing unused property behind our house, and you may recall we had a 1/2 acre cleared a few months ago for the RV parking pad. I had in mind leaving adequate space for the solar racks when we did that..."

Just thinking; What about using the solar panels as a "Roof Over" for the motorhome on its new pad. If you are going to build a ground based system, elevate it above the coach, can't be that much more cost...

Re: Solar Question for Gurus

Reply #24 – February 10, 2022, 08:48:41 am

Quote from: Gerry Vicha – February 10, 2022, 07:16:43 am

Just thinking; What about using the solar panels as a "Roof Over" for the motorhome on its new pad. If you are going to build a ground based system, elevate it above the coach, can't be that much more cost...

I like the way you think, Gerry. I have already considered that option, and it is still on the table. However, I have so far had a hard time getting anyone interested in building me just a plain-jane flat RV cover. Adding complexity to the design doesn't help the cause.

With our almost constant winds, any carport or RV cover around here needs to be strong. The higher off the ground, the more it is caught by the wind. Steel is really expensive right now. More steel = higher cost.

Most of the prefabricated solar ground mounts I've seen are pretty simple and relatively easy to install. One of the nice things about having the panels down at ground level is they are easier to keep clean. Battery powered leaf blower, or water hose and squeegee. We get a lot of blowing dust in West TX. My next door neighbor has 20 solar panels on his roof. He gets up there and tries to clean them off, but it's a big hassle. His wife is afraid he'll fall off and break his neck.

I will wait to hear what the salesman says today. When we discuss panel mounts, I will ask about building them into a RV cover.

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