First, considering the technology used for measuring gas and diesel at filling stations, where the pumps have digital readouts which can be read in the building and at the pump, can be programmed, and measure accurately to the milliliter, why are we still using rusty old balance scales and paper slips to sell propane?
Second, why is propane still sold by the pound when Canada has been using the metric system for almost 50 years? I just had a 20 lb tank filled last night, and printed right on the receipt was the price per pound.
There seems to be a disconnect with measurement devices and units between fuel types at the same filling station in the present day. Why?
Alberta here. I haven’t seen such a thing in ages. I can buy pre-filled tanks from the local gas station, and they will take a trade-in of my empty tank, which lowers the price of the pre-filled tank.
I’m not sure about other provinces though. Where did you see this?
Weight is more accurate than measuring by volume. Volume is affected by the temperature while weight is not. Propane is still sold, where I live, by weight exactly as you describe.
I wish gasoline and diesel were sold by weight also. I have gotten diesel in the past that was hot enough that you needed gloves to pump it. They explained that it was to keep the diesel from gelling. In the summertime?
If I’m not mistaken, propane is metered when it’s used to fill vehicle tanks, such as the propane taxis common around here. I imagine one of the reasons for using weight scales for portable tanks is that most places have a fixed price for any given size of tank, so it keeps everything simple – if you’re bringing in an empty 20-pound tank you sort of expect to get 20 pounds of propane at the posted price.
I don’t like the tank-exchange systems. I like to keep my own tanks of known quality, which also have liquid-level sensing gauges on them.
What I’ve seen is you bring in a tank that weighs some unknown weight. With some other unknown weight of residual propane in it. Not much, but some.
So they weigh the tank + propane you brought. The total is now known even if the breakdown isn’t. Then they fill it and weigh it again. You pay $X/lb for however many pounds and ounces of difference between the before and after weights.
I’ve also brought in tanks that were half or 3/4ths full because I wanted to top them off before a big event or a trip. The tare is larger and the fill is smaller. But I’m only paying for what I bought, not what I brought.
The alternative is tank exchange: pay a flat price for a full tank and leave your old one, residual propane and all, at the store. Which of course encourages people to use them down to the last drop. Inconvenient though it may be when the fire goes out.
It probably also has a lot do do with delivery system. Here in Oz I see both high accuracy volumetric delivery for vehicles, and very basic weight when filling cylinders. For vehicles the source is usually a large tank, and the end to end delivery is done in a very controlled manner - with no leakage and no doubt an end to end path of liquid propane. Filling a portable cylinder is just a matter of attaching it to a bigger cylinder, opening the exit valve and letting pressure push liquid out of the bigger cylinder until the small cylinder is full. Very cheap, messy. lossy, and inexact. Being lossy you would want to only be paying for what made it into your cylinder, not also what was wasted in the process. (Usually now one does just pay for a refill rather than the mass of what went in - but the principle remains.)
The nice thing about cylinder exchange here is that you can exchange an empty out of test cylinder for a full one. It is illegal to refill an out of test cylinder, but the cost of changeover includes the costs of maintaining the fleet of cylinders, and they adsorb the cost of retesting (and the occasional failure to meet test. The margin between having you own cylinder refilled versus just exchanging the cylinder is $5 - and given you don’t have to hang about waiting to have your own cylinder refilled - and can also find 24 hour places that will do an exchange - it is a pretty good deal.)
It’s the opposite everywhere I’ve seen it here in Ontario. It’s a fixed cost for any given volume of portable tank, of which the vast majority are the 20-pounders. I suspect that the weigh scale is, at least in part, a safeguard against dangerous overfilling.
Selling by weight is simple. It doesn’t require any special equipment on the part of the seller (scales are cheap and useful for many things). Also, it’s easy for customers to verify that they got what they paid for.
Is it possible that it’s just the one store that sells by the pound (i.e. not the metric system), or is it like that all over Canada?
LSLGuy & Francis Vaughan pretty much got it between them.
When you bring a 20lb tank in for a fill they don’t know how full or empty that tank is. What they do know is the tare weight of the tank. By weighing the tank before they fill it they know how much propane is in it (Propane weighs 4.2 lb / gallon). By weighing the tank afterwards, they know how many pounds of propane they put it & therefore how many gallons they put it.
The tanks that I fill on a regular basis are much larger, anywhere from 10-25 gallons & can weigh over 100 lbs when full. We don’t unstrap them & we don’t remove them, just fill them right in the basket. Of course, they have spit valves. When you open the bleeder valve & it starts spitting, you know the tank is full. Close the spitter & turn off the hose, then purge & uncouple. These are all filled via a gas-pump style meter that is counting the gallons used. We then pay the # of gallons x price/gallon.
Here in the USA the 20 pound tanks only hold 17 pounds. Due to the overfill prevention valves required several years back. That’s for residential BBQ type tanks anyway. Industrial tanks I don’t belive have the valves.
We purchase it in bulk by the litre and dispense by the pound. Mind you, we’re primarily a building supply store and most of our fasteners are sold by the pound and the dimensional lumber is by the nominal inch (our rough cedar is full dimensional).
I believe most of this is industrial inertia, and is field wide. The prefilled propane cylinders we sell for torches and portable barbeques are marked as 16.4oz / 465g or 14.1oz / 400g tanks.
Grocery stores are still pricing meat & veg by the pound as well (the /kg measurements are always posted on the tags and in the ads, but the large print is always the pound price) except deli slices by the /100g.
I’ll throw this out there. The methods are different because the business is choosing the cheapest method to dispense fuel.
Gas and Diesel are both liquids, and a volumetric system for dispensing these liquids is faster and cheaper than a weight based system, as you would need large, highly precise scales and require people to park their cars directly on the scale before pumping, and require them to not add or remove anything from the car during the pumping process.
Propane is held in a pressurized state, and delivered to small portable containers. Small portable containers are trivially easy to weigh with very inexpensive equipment. Changing to a volumetric system will not improve accuracy or speed of delivery, but will introduce an expensive delivery system that is more prone to failure than a small scale.
Hmm. Thanks for the info. Color me surprised. Two adjacent similar countries / states / provinces doing things exactly opposite; who’da thunk it?
As **Spiderman **describes above about larger tanks, in US practice a portable 20# tank is refilled at a retailer by opening the tank’s overflow valve with a small screwdriver, then turning on the flow of liquid gas coming into the tank through the main valve. When the overflow starts overflowing, it’s full. Close both valves and pay for the weight delta.
Because the stuff is liquid at conventional temps under only moderate pressure it can be metered as a liquid too.
I have to say I’d be pissed if I brought in a half-full tank to be refilled before a trip only to find them charging me full price for just half a tank of propane.
I’m in Alberta as well and I have the option of either refilling the tanks or taking them to an exchange (Canadian Tire, usually). As noted, when I refill the tanks the attendant checks the expiry, places it on the scale, “zeroes it” and then proceeds to fill. By law they aren’t allowed to fill beyond 80% capacity IIRC. To the OP, when the question is why more often than not the answer is money. It’s the same reason why they temperature correct the volume to 15C as it enables them to buy less expensive equipment, for one thing.
