House Battery and Energy Management

[italianuser]

Wow great job! You're asking yourself many questions and finding the answers, very good

Maybe I missed a description, but is your battery right next to the water pipes or am I wrong? As for risk management, did you consider the case "Pipe breaks and water goes everywhere?"

 

[rebelrider.mike]

Thanks!

Yeah, I've got the water pipes drawn in so as to stay aware of their location, and also for thinking about possible leaks or breaks. Its extremely unlikely that such a thing would occur. But not impossible.

One bit of luck: EG4 just released a new outdoor-rated wall-mountable battery that would eliminate my need for the 3 batteries and battery rack I had planned on getting. Its like they designed it with me in mind specifically. It is huge-ish and will have to sit on the floor, but would still be anchored to the wall. Its water-resistant, and should easily withstand water pipe leakage and a bit of standing water on the floor.

My basement floor is actually sloped, with the battery and clothes washer area being the high spot. So any water on the floor would go towards the floor drain, or if that were clogged, towards the door to the back yard. This one time, our sewer pipe backed up into the basement (that was gross) but the puddle never made it as far as the clothes washer. Another time, the clothes washer had an internal pipe come loose, but the water went out the door.

Anyway, I think the plumbing will be ok. But if I had to, I could move it. I really need the outdoor spigot in that location though. So we'll see what happens.

 

[prepared1]

Just a friendly suggestion that I've found to be a good practice with old houses: I always mount the electrical service either on Unistrut mounted to the wall, or attach a couple of sturdy 2x4's to the floor joists and let them hang down far enough that you can mount a sheet of plywood on them for your panels. I usually paint the wood panel just to make it look cleaner. I've also lagged pressure treated wood directly to the walls, but don't like that as much.

Over the years, moisture gets in them directly from the wall, or tiny leaks. What-ever, they end up rusty. Some sort of stand-off can also make for a nice chase way to run conduit, or to help hide feed wires. Keep in mind that in most cases, the service has to be within 6' of the entrance point, or you need a disconnect. That varies with jurisdictions.

It is a hassle, but in the end is well worth it.

Good luck with your project!

 

[OffGridInTheCity]

Just a friendly suggestion that I've found to be a good practice with old houses: I always mount the electrical service either on Unistrut mounted to the wall, or attach a couple of sturdy 2x4's to the floor joists and let them hang down far enough that you can mount a sheet of plywood on them for your panels. I usually paint the wood panel just to make it look cleaner. I've also lagged pressure treated wood directly to the walls, but don't like that as much.

Over the years, moisture gets in them directly from the wall, or tiny leaks. What-ever, they end up rusty. Some sort of stand-off can also make for a nice chase way to run conduit, or to help hide feed wires. Keep in mind that in most cases, the service has to be within 6' of the entrance point, or you need a disconnect. That varies with jurisdictions.

It is a hassle, but in the end is well worth it.

Good luck with your project!

It's an interesting topic. My powerwall is underneath a bathroom.... and when the toilet clogged/backuped-up I started plunging.... too hard and caused water to leak at the toilet/floor seal. So much water it dripped thru onto the battery bank!! Got lucky in that I noticed the issue and stopped plunging and dried things up - but the episode highlighted (for me) that water can be an unexpected issue!

I have corrugated metal over the battery bank to slow fire from going up thru the floor but also acts as an umbrella as I found out. So water protection?

 

[prepared1]

OGITC: The first thing I tend to do with buildings is to deal with issues like those. One of our buildings has the water meter 6 feet from the 200 amp panel, but then they put an outdoor spigot 1 foot to the left and above that same panel. Not a great idea here in Iowa where it gets cold and things freeze hard. So I'm moving the spigot, and mounting a new panel on Uni-Strut. I really dislike a panel bolted directly to concrete, because they rust. We paint all our concrete walls with a couple coats of KILZ, and that does help.

Over the years, I've had very good luck calling the power company and asking them to come pull my meter for a few hours, so I can move a water line or drain in the vicinity to someplace safer. I have never been refused, and not once have they ever told me to get a permit. An inspector told me 40 years ago that if you moved a water line and it leaks, you will fix it pronto. They are much more worried about people who don't know what they are doing, and people who don't fix things.

Hey, by the way, I recall that I read something in the 2020 NEC, or possibly in supporting doucments that referenced not having a combustion device in the same room as an ESS, or UPS. Something like that. When I asked the AHJ about it, he politely said he really didn't know, but suggested not even having a gas line in the same room. I'm still pondering that one. Sorry, that is a bit off topic of the OP.

 

[prepared1]

Thanks!

Yeah, I've got the water pipes drawn in so as to stay aware of their location, and also for thinking about possible leaks or breaks. Its extremely unlikely that such a thing would occur. But not impossible.

One bit of luck: EG4 just released a new outdoor-rated wall-mountable battery that would eliminate my need for the 3 batteries and battery rack I had planned on getting. Its like they designed it with me in mind specifically. It is huge-ish and will have to sit on the floor, but would still be anchored to the wall. Its water-resistant, and should easily withstand water pipe leakage and a bit of standing water on the floor.

My basement floor is actually sloped, with the battery and clothes washer area being the high spot. So any water on the floor would go towards the floor drain, or if that were clogged, towards the door to the back yard. This one time, our sewer pipe backed up into the basement (that was gross) but the puddle never made it as far as the clothes washer. Another time, the clothes washer had an internal pipe come loose, but the water went out the door.

Anyway, I think the plumbing will be ok. But if I had to, I could move it. I really need the outdoor spigot in that location though. So we'll see what happens.

Everybody is all excited about the new batteries, but those things have been made in China and Japan for many years. They just didn't sell them much in the US. In my travels around the world for my job, I came to the conclusion that we are generally far behind Europe and Asia when it comes to technology. In 2004 I spent a day in Germany marveling at how you could walk into a giant store, and walk out with solar panels, solar hot water systems, all sort of centralized control systems, really superior wiring systems, etc. That also goes for mini-splits in Japan, etc. Now they are making a big deal out of making videos on them here in the US, so influencers can get paid. Too funny.

But I really laughed when I watched a video of a trade show where Schneider was touting their "new" solar ready Square D panel.....a split buss panel. I have a 200 amp Square D panel from 1963 that is the same thing, and it turns out they had them in the 50's. But hey, it is marketing.

Signature Solar is making the effort to offer some good products here, so good for them! And I do like the look of that 300# battery, but there is one big issue that would keep me from buying it. A single point of failure, and you are out of luck. I'd much rather have 2-6 of them, smaller, lighter, take them out if they fail.

 

[rebelrider.mike]

Availability in other countries does me no good though. It has to pass the local inspection, and be available for me to purchase. I've seen lots of great products that I can't use because of those reasons.

Maybe someone will do a teardown video of the new battery. I bet we could figure out how to fix a broken one if we really want to.

I haven't had any issues with my main panel rusting on the cinder block wall. I think it's been there since 1996. And I recall manuals for several inverters I've looked at recommending installation on concrete or other non combustible surface.

I think you're right about the NEC wanting separation between batteries and combustion sources. I believe that is mainly for lead acid since they can outgass hydrogen.

 

[rebelrider.mike]

I've been watching a lot of You Tube videos from folks like Mayfield Renewables, Mike Holt NEC, and Electrician U, to help me understand WTH the NEC book is actually trying to say.

Today's struggle is 705.12. Tentatively, I think they are saying that I can have 2 power sources on my main panel if the breakers don't add up to more than 120% of the bus bar rating. I have a 225A rated main panel, with a 200A main breaker. So that would allow me to add up to 70A from another power source (like a solar inverter) as long as I place that breaker as far away from the 200A breaker as possible.

The specific location of the second breaker means I have to relocate the transfer switch, and use an extra foot or so of conductors. Not ideal, but I can make it happen.

I've also been looking into the idea that some inverters, like the EG4 18k, can send power to both a load panel and the main panel. I hadn't considered this before; assuming that with a full battery, any energy not needed for the load panel would just be unused potential. Now I'm thinking I could send that excess power to the main panel (since the inverter will have that capability in order to comply with code anyway) and that otherwise wasted power could actually be used. Selling power back to the grid isn't a priority for me, but I'm not against it either, so long as the PUD doesn't make me jump through too many hoops.

Anyway, I re-calculated my energy savings based on the assumption that I could use all the energy from my solar array, and not just what my optional loads circuits would use. It actually made a nice dent in my ROI. I went from 31 years to 26 years.

Now this is all based on monthly averages. I'm assuming there will be times during the day that I would produce more power than I need, even for the whole house. Even if I were able to sell that energy back to the PUD, I'd get pennies for what I'd pay dollars for, right? So money-wise, it's still pretty much wasted potential energy. But at least someone out there could potentially use it.

Here's a graph based on whole house energy consumption, and updated numbers from my current solar array design:

I'm hoping this will change pretty radically once I trade the electric furnace for a heat pump, and other efficiency improvements are made.

 

[rebelrider.mike]

I made some progress yesterday:

The ATS is now fastened to the wall, and the conduit is installed. I've also rearranged the circuit breakers in the main panel so the 50A 2-pole breaker that feeds the sub panel (and eventually the inverter) is as far away from the main breaker as possible. It's hard to tell in the picture, but I've also got the 20A breaker for the new clothes washer circuit on the sub panel. I re-drilled the holes for the clothes washer receptacle box, and it is now secured with proper concrete screws.

Next is to run some wiring, and get one conduit fitting I need so I can finish the clothes washer circuit. My son and I cleaned out the shed yesterday, and we found the soffit vent covers I've been looking for. One step closer to ventilating the attic.

 

[Korishan]

Those Emporia units are nice, but sure wish there was a better way to handle that rats nest they create with all those sensor wires Mine doesn't look much better than what yours currently does, including hanging outside the panel Of course, where the panel is located I don't have to worry about kids, animals, etc getting into it.

I actually reflashed mine to be ESPHome so I can keep the data local and I can fine tune the results easier.

 

[OffGridInTheCity]

Careful - before you know it you'll have a beautiful, clean install!

 

[rebelrider.mike]

Yeah, I don't know if it will work, but I hope a side product of this is that the wiring will end up looking nicer. The Vue's permanent home will be in the sub panel, so I'm going to try to do some cable management in there. And so many circuits are leaving the main panel, I hope to clean things up in there too. We'll see how it actually turns out though.

 

[rebelrider.mike]

I've been working on getting power to the sub panel, and I hit a snag. The ATS I'm running the power through, has connections on its contactors for the neutral wire, so it can be switched. This is fine if you have a permanently wired generator that has a neutral to ground bond. In my case though, I'll have a portable generator that may or may not be plugged in. Another thought is that the generator won't have its own grounding electrode. So even if it were plugged in and bonded, would it matter?

Now, people can't seem to agree on how grounding stuff should work. The NEC is so poorly worded that people can't even agree on what the NEC says to do about grounding. So what's an idiot like me supposed to do? That's right: draw pictures.

I made some examples of how I might wire the ATS. First is with a bonded generator. I think this would be fine if the generator were permanently installed, hard-wired, and either had its own ground rod, or were connected to the one for the house. I'll have a portable generator which could very well be unplugged, and won't be connected to a ground rod. So switching off the neutral from the main panel will cause everything down-line to have a floating neutral during a power outage. That's the second example.

In the third example, I thought of putting in a jumper between the grid and generator neutrals. But that still won't work if both contactors are open. If the grid is out, and the generator is not plugged in, both contactors will be open. Plus, its possible to lock both contactors out manually. I don't know why I would, but the possibility is there, creating the same problem.

So I decided to skip the neutral contactors and wire the neutrals all in common like a regular junction box. (Fourth example.) Solved all problems... I thought. It turns out (I think) the coils that operate the contactors run on 120V, and need power to the neutral inputs in order to function. So each contactor is going to need a neutral input, even if there is no neutral output. I believe I can solve this by running some jumpers from the neutral junction to the inputs on the contactors. I've ordered a fancy tap connector to do the job.

Here is the diagram that comes on the back of the ATS cover:

Connecting the output wires is a little challenging. In order to see, I've had to remove the contactor assembly from the box. The two contactor's set of three outputs are tied together with insulated bus bars. (Is it bus or buss?) Anyway, either contactor output set could be used, but I'm using the grid contactor output so the bus bars will be unused most of the time. And when they are used, they'll only be conducting a maximum of 30A from the generator. I've only got 1 bus bar installed in this picture:

I temporarily removed the others so it would be easier to see.

 

[rebelrider.mike]

The sub panel has power!

The tap connectors I ordered for the 6AWG neutral wire was delivered today, but I didn't receive it. I wonder if my package ended up at Burger King again. So the neutral wiring is temporary until I can get the right parts. Now I can run my clothes washer from a proper GFCI receptacle instead of one of the light circuits. I've even got the Vue sensor back on the clothes washer circuit.

Even though its not a priority, I've started looking into what it would take to get a sell-back agreement with my utility. It's actually pretty strait forward. I submit diagrams, manuals for the inverter and other stuff, pass and inspection from L&I, that sort of thing. I was surprised though that I'll need a solar permit from the county. I have no idea what kinds of rules they'll want me to follow, so I'll have to stop by and ask sometime.

My utility does a kWh credit system. So if I send a kWh into the grid, I get a credit for 1 free kWh back later. Any accumulated credits expire each year in April. But I figure any that I make will be long used up by then. Seems like a pretty good deal to me.

I got my clamp meter out to see how much power the contactor in the ATS uses to stay contacting. 0.14A, or 16.8W. That's a bit of efficiency that I'm trading for the happiness of having an automatic contactor. While I had the clamp meter out, on a whim I measured one of the GEC wires going out to the ground rod. I got 0.45A. I know that there is always some current leakage to ground in a normal system, but I don't know how much is considered acceptable. I've also got a second ground rod and metal water pipe. The wires to them don't show any current at all. Weird.

I looked at the wiring diagram for the generator I'm thinking of getting. Here is a closeup of the receptacles from their manual:

I added color to make it easier to read. Seems the L14-30R receptacle that I would be using has no over current protection and no ground fault protection. I'm pretty sure I need both to comply with NEC. I've decided to add a 2-space load center between the generator and the rest of the house, with a GFCI breaker. It won't protect the generator (ground fault wise) but should protect what goes into the house and comply with code.

I've also been thinking about how I want to use the generator once the inverter is installed. I'll be able to use it to power the sub panel independent of the inverter if I had the need. But I'm also thinking about getting an EG4 Chargeverter so I could charge the battery from the generator instead of running the sub panel. But I don't want the generator trying to run the sub panel and the Chargeverter at the same time. Since the generator can only output 30A maximum, it's a lot easier to find parts rated for that current. I found a 30A DPDT on-off-on switch that will let me choose where to send generator power without having to plug or unplug anything. Here's a picture that shows what I'm thinking of:

I also updated the ATS to include the neutral jumper wires. The Chargeverter would pull up to 26A from the generator to deliver up to 100A to the battery. This seems to be a really good way to charge the battery during a power outage, with or without solar panels. Also, the unused generator port in the inverter could be switched over to something with "smart loads". I don't know what that is yet, but it will be nice to have the option if I ever get one.

 

[rebelrider.mike]

Found my multi-tap connectors. Turns out they were under my box in the mail room. Not sure how they got there, but at least I found them. I got one installed in the ATS today, and now the neutral cable to the sub panel is finished.

I found many feet of 12AWG white THHN wire in my dad's stash, so I used that to connect the contactors to the neutral so they can have power. The contactors use so little power that 16AWG would have worked, but the 12AWG was free, and easier to get good solid connections with. Next up is to get the parts for the generator circuit and start hooking them up.

I finally got to L&I yesterday and bought a permit. It turns out that by claiming (as a homeowner) not to need a licensed electrician, I'm also claiming to know all the things about the electrical work I'm doing. So they're not too interested in answering technical questions. They do have a number I can call between 8am and 8:30am, and I can ask 1 question per day. If it's not too stupid.

I also went to the county building department to ask about their solar installation requirements. The only requirement I have an issue with is that they require an engineer to design whatever mounting system the panels will be on. No exceptions. So now I have to find an engineer willing to design my pergola, and see how expensive they are.

One bit of good news: I reread the NEC (again) and it seems that I don't need to have GFCI protection on the 240V receptacle on the generator. GFCI is only required on receptacles that feed devices that are handled directly by people. A cable going into the house doesn't need it. I still want a 30A breaker between the generator and the ATS, but now I can install a regular one. That'll save me $80. I guess I can put that towards the engineer's fees.

 

[rebelrider.mike]

I've been giving the county solar permit issue a lot of thought. Rather than trying to find and hire an engineer to design my solar panel mounting system. I may as well hire a solar contractor. I was hoping to avoid that, but it seems everything I want to do is illegal. Story of my life.

Anyway, I've been thinking of the pros and cons of getting a contractor vs. DIY.

Pros:

• They'll take care of all the permits.
• They know all the codes and requirements.
• I'll be eligible for various incentives that I wouldn't qualify for if I do the work myself.
• They'll know how to get me those incentives.
• They may have better ideas as to where and how to install panels.
• I can call on them later to repair any major incidental damage.

Cons:

• I fear that even with incentives, their installation will cost far more than my DIY plan would.
• I fear they will start telling me a bunch of stuff I can't do because of some company policy.
• I wonder how much of the installation they'll let me do. Probably none.
• They're going to want to do things their way; not my way. I hate that.
• I may end up with a system that I can't maintain or repair myself.
• Every contractor I've ever hired has been almost impossible to get to show up to work. I fear more of the same.
• I won't be able to spread the cost out over time, like I'm doing now. Getting a loan is gonna hurt.

Perhaps my fears are unfounded, and I'll just get over the parts I just don't like. For now, I will continue with phase 1: sub panel and generator installation, and also do phase 2: install the house battery and inverter. Those don't need an engineer or contractor. And I'll have more time to see if a better solution presents itself.

Some good news: I've been poking around in the NEC, and I found article 250.122: Size of Equipment Grounding Conductors. I was surprised to see that it is not like I thought it was. I've always thought that the ground wire is supposed to be the same size as the current carrying conductors. But this turns out to only be true for 15 and 20 Amp circuits.

I have thought for a while that surely we don't need a 2/0 AWG ground wire for a 200A battery. But also surely, there must be a minimum size for a ground wire that only grounds the metal battery box? Turns out there is: A battery on a 200A fuse or breaker only needs a 6 AWG ground wire. This makes sense to me as my 200A main panel only has a 6 AWG copper wire going to the ground electrode. Although, technically, the wire to my ground electrode is a grounding electrode conductor, not an equipment grounding conductor. There are different rules for those.

Maybe everyone else already knows this? It's news to me. And I've seen the question asked before, and I've only ever read responses like "I don't know" and "ask your AHJ". I'm happy to know there is a specific table in the NEC I can reference.

 

[OffGridInTheCity]

For my initial system I did 2 things....
1) For the PV array, used IronRidge system which included engineering docs designed for most permit jurisdictions and were acceptable by my city. Maybe IronRidge or some other top-tier PV array mounting company has something similar you can use to do DIY like I did.
2) For the electrical I found an electrician that was acceptable to the city but also let me do 70% of the actual work / explained things to me. This was invaluable when I expanded later on.

An expert 'con' example. 4 yrs ago, when I replaced my 23yr-old gas furnace + traditional AC with a whole-house heat pump they installed it all right but neglected to tell me the permit was my problem. 4 months after the install I got a call from them that I needed to do the permit. For the $ I paid I was livid - but at that point there was nothing I could do but do the permit process myself.

In conclusion....
1) If you go with 'experts' make sure that who does the permits is IN WRITING as part of the contract.
2) You may be able to do more than less DIY with a little expert help - part contractor and part DIY. It doesn't have to be 100% one way or the other.
3) Patience is good. When I pulled the Solar permit I went downtown and gave the application... and they made me sit for 4 hours waiting on them - ignoring me the whole time when I would go up every hour and try to ask about progress in approval. When I asked should I come back tomorrow they ignored me - daring me to leave (it felt like). They did approve it but I think I was being pushed around a little.

Following along to see how it goes and wish you the best

 

[rebelrider.mike]

Thanks, that is interesting. Where I live, he who does the work is legally required to get the permit. When I get my furnace upgraded to a heat pump, we'll need an electrical permit from L&I (I will get that) and a mechanical permit from the county (the HVAC company will need to get that). I'll need both inspections to get a substantial rebate from my utility. So the HVAC people will not be getting paid their final payment until the mechanical passes inspection.

I suppose I better work that stuff out in advance with whoever I hire to help me with the panels.

I see a big difference between experts and professionals. A pro is someone who gets paid for their work. Doesn't mean they're good at it. I've seen some very professional in my time. And experts aren't always paid. I've seen DIY stuff that blows the pros out of the water. I hope I can find a professional that's also an expert.

Meanwhile, I've started shopping around for some kind of protective cover for the inverter. I've been wanting a sort of awning or porch cover for the basement doors for years, so I think I'll take care of both at the same time. I found one made of polycarbonate that is 156" wide, and 38" deep. A single unit could cover both. I made some drawings (surprise!) to see how it might look:

I'll have to modify it a little to fit around the power mast, but I think that can be easily done. As an added bonus, I'll have some weather protection for the door and frame. The current ones have a lot of rot and moisture damage from weather exposure. I plan to replace them next summer. So this awning will hopefully give the new doors and frame a longer life than the current set.

 

[rebelrider.mike]

I managed to get a free propane tank! Larger than the regular ones you see on BBQs but still portable. I had it recertified, and filled. It holds 100 lbs of propane, and will live next to the generator probably. If I'm reading the stuff on it correctly, it weighs 171 lbs when full. I am just barely able to handle it on my own.

In its previous life, it sat in direct sunlight for many years. The paint has sort of turned to dust. I think I'll repaint it next summer.

Turns out I made a big mistake calculating the cost of running the generator from propane. I get lbs and gallons of propane mixed up. Turns out propane is actually slightly cheaper than gasoline per Wh. I went back and updated some of the math I did way back when I was estimating minimal power usage during a long term power outage. 100 lbs of propane should last almost a month based on current solar estimates and battery capacity. So that's pretty cool. I'd need 16 gallons of gasoline to do the same thing. That would be a lot of gasoline to store. I don't think I'd want to store more than 5 gallons at a time.

I haven't got much else done this last month. I think I have all the parts I need to install the generator inlet to the ATS. I just haven't done it yet. I did start tracking my furnace's energy usage this last April, and I've made a couple tables to see what it's doing. I'm curious as to exactly what percentage of my total energy bill the furnace represents. So far, it's 43%. But that's only between April through October, so I bet by the end of March that number will double.

I've been researching heat pumps again, and hoping to find a way I could use my existing furnace energy usage to estimate the energy usage if I had a heat pump instead. Unfortunately, it's not a direct ratio, as the heat pump's efficiency changes with the outside temperature while the furnace's does not. I was hoping to find some kind of temperature coefficient like on solar panels, but so far no luck. There are calculators on line, but most are pretty bad. Either they don't include variables that I think are really important, or they're mostly just trying to sell stuff. I did find one that seems pretty legit: https://heatpumpshooray.com/. They claim I'd save 75% per year. If that's true, then it would certainly be worth taking out a loan to get it done.

Since I don't have real numbers to work with yet, I made some up based on past trends. Assuming we use roughly 400 kWh/m of electricity on non heating and cooling things each month, I can see over the last 12 months how many kwh we used by subtracting the known total by the estimated 400. So whatever's left is heating and cooling. I added the cooling because I'm hoping to use the heat pump instead of the window A/Cs that we've got around the house.

Those results were interesting. Of the $2,820 I spent in the last year directly on electricity, $2,380 of that was spent heating or cooling. About 84%. If that's anywhere near correct, then the heat pump would pay for itself in about 8 years. Less if I'm able to continue making the house more efficient. I'm also looking for any installation incentives that might be available. So far, I've seen a rebate from my PUD, and there might be an IRS form that might get me something. I've heard rumors of an inflation reduction act, but I don't think it's available in my state. Maybe in the future.

As far as solar installation, I've tracked down 3 engineering companies and 2 solar installers that are licensed for the sort of work I need to make the county building department happy. Two engineers in particular seem well suited to assess my old deck and come up with a plan to upgrade it with a solar cover. I'm hopeful that we'll be able to work something out.

 

[Korishan]

100 lbs of propane should last almost a month based on current solar estimates and battery capacity. So that's pretty cool. I'd need 16 gallons of gasoline to do the same thing

Not only that, gas will degrade over time, even with stabilizer in it.

Side note: Even tho Technology Connections did a video recently on 3 year old gas with stabilizer in it and it ran his snow blower just fine, what he did not account for was efficiency of that fuel. Sure stabilized old gas may still be ignitable and start the engine just fine, however, does it still use the same amount of fuel to air ratio as fresh gas?? I'm guessing no

Keeping propane on site is a lot safer too. From a storage perspective, and also a burning perspective, as the only byproduct of propane is mostly just water vapor (there's some CO/CO2 and tiny bit of NOx but that's because of some of the oil that gets past the cylinder rings)

Propane prices are relatively stable. Our local refilling station hasn't changed prices in 5+ years. $20 for 20lbs, and they fill it completely right up to the bypass valve

Second Side Note: when ever possible, never ever ever get your fuel from Home Depot, Walmart, or any other store where they have "quick swap tanks" available unless you are specifically needing to the change the "tank". The reason is that these locations only sell 15lbs of propane in the tank, not the 20lbs, and it costs more at these locations. Go to an ACE, or some other refilling station.