Automatic Deliveries and Degree Days


Are you on automatic delivery for your fuel? Have you ever wondered how we know when we should fill your tank? Of course, we could come once a month every month and top off your tank, but what if you’ve only used a few gallons because it’s been warm? Or maybe there was a really cold snap and you had your heat cranked way up. And while you might set your thermostat to 65 your neighbours have theirs set to 73 – you won’t burn as much as they do. But if you both had a delivery every month, regular as clockwork, we’d be forever bringing you small deliveries, which wouldn’t be cost effective, and your neighbour would repeatedly be on the verge of running out, which would be annoying… at best.

So, how do we do it? Well, there are two factors that come into play: The first is the weather – if it’s warm you burn less, if it’s cold you burn more. The forecast is important – if the meteorologists are telling us we’re heading into a cold snap and you’re due for a delivery we may come a few days early, just to be safe. But we also need to keep track of the passing weather so we can estimate how much fuel you’ve burned and when you might need a delivery. To do that we use ‘Degree Days.’

There are two types of Degree Days – Heating Degree Days (HDD) and Cooling Degree Days (CDD). For the purpose of our fuel deliveries we pay attention to the HDD. But how do we calculate the HDD? Let’s say that one day this winter the average temperature was 35°F. We take a base rate of 65°F, subtract 35 from it and we get 30. So, for that particular day we had 30 HDDs.

Now, we look at your property. Your account records tell us how much fuel you burn – after two or three winter deliveries we can give your property its own unique usage rate, designated by a K-factor. The K-factor = the number of HDDs that will cause your property to burn 1 gallon of fuel. Thus, your actual usage will be the HDDs divided by the K-factor. The lower your K-factor the more fuel you will burn. For example, if your K-factor is 5, then over 30 HDDs you will burn 6 gallons, but if your K-factor is 10, then over 30 HDDs you will burn only 3 gallons.

Finally we need to know the size of your tank. Let’s say your tank holds 500 gallons of fuel and your K-factor is 10; 500 x 10 = 5000. You will use a full tank of fuel in 5000 HDDs.

In the past our delivery manager spent most of his winter days recording HDDs, calculating the accumulated total every day, and then figuring out who needed a delivery. Today, we have computers to help. On a daily basis our delivery manager checks the computer and sets up a delivery schedule for any property that needs fuel – based on a) the property’s K-factor, b) how big the tank is, c) when the tank was last filled, and d) the accumulated HDDs since that last filling.

So why does the system fail from time to time? Because the formulae cannot take human impact into account. There are countless reasons why we might burn more or less fuel than normal: perhaps there’s a new baby in the house so the heat has been kept 3 or 4 degrees higher than last winter. Perhaps a basement window was left open and so the system has burned more fuel to keep the house to the thermostat temperature. Perhaps you went away for a month and turned the thermostat down to 50°. Perhaps the fuel also heats the water and your then favourite relatives came for the Holidays and took multiple showers and baths every day! Whatever the reason, if you know that you’ve used more than normal, it’s always a good idea to let us know – you don’t want to run out, and we don’t want you to run out. After all, a run out means a special delivery and that always ends up costing somebody something.

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