The estimator converts a gauge reading into remaining days based on your own historic consumption and the time of year, and tells you when to reorder to keep a working reserve.
Why a percentage is not useful
A gauge tells you the tank is a third full. That is not an actionable number, because it does not tell you whether that is three weeks or three months.
What you actually need to know is:
- How many weeks of heating that represents, at this time of year.
- When to order so that the delivery arrives before you reach a quarter tank.
- Whether the current lead time for deliveries fits inside that window.
The estimator does that conversion from your own consumption history, which is far more reliable than any rule of thumb based on property size.
What it uses
- Your tank capacity.
- Current level, from the gauge or a dipstick.
- Your historic consumption, derived from previous delivery quantities and dates. This is the key input and it is specific to your house.
- Time of year, because winter consumption is a multiple of summer consumption.
- Whether hot water is on the same system, which gives a year-round baseline.
- Typical delivery lead time for your area and season.
Property size, bedroom count and floor area are poor predictors of oil consumption, because insulation, occupancy, thermostat settings and boiler efficiency all vary enormously. Your last two or three deliveries, with dates, tell you more than any generic model.
The reserve rule
The estimator’s default target is to reorder so that the delivery arrives while there is still around a quarter of a tank left. That is not caution – it is maintenance.
The bottom of an oil tank holds a layer of settled water, sediment and degraded fuel. In normal use the outlet draws from above it. Running the level right down draws that layer into the supply line, which blocks filters, can reach the nozzle, and occasionally damages the pump. A run-dry in December becomes a filter change in January and a pump in February.
Keeping a reserve also means you are never the person ordering during a cold snap, when lead times extend from days to weeks and everybody wants a delivery at once. See buying heating oil sensibly and running out of oil.
Gauges, and why they mislead
| Gauge type | Reliability | Notes |
|---|---|---|
| Sight tube | Poor to fair | Discolours, perishes, and a failed one empties the tank onto the ground |
| Float gauge (clock face) | Fair | Mechanical, and sticks. Reads wrong without obviously failing |
| Dipstick | Good | Accurate, and only works on tanks that allow it |
| Electronic ultrasonic | Good | Reads remotely, often with a low-level alarm. The most useful for avoiding a run-dry |
| Electronic with app reporting | Good | Adds remote visibility, useful for second homes and rural properties |
If you have ever run low, an electronic gauge with a low-level alarm is inexpensive relative to a blocked pump and it removes the problem entirely. It also alerts you to a sudden unexplained drop, which is the usual signature of theft.
What it does not do
It does not tell you what oil costs or predict prices. We have no licensed source for heating oil price data and we will not publish figures we cannot stand behind – see what things cost.
It estimates from your consumption history, so it is only as good as that history. A house that has just had insulation done, changed occupancy, or had a boiler replaced will consume differently and the estimate needs a season to recalibrate.
And it does not replace looking at the tank. A gauge reading is a data point; the tank’s condition is something else entirely, and it is worth ten minutes in the spring – see eight signs an oil tank is near the end of its life.
The architecture for it is defined and it is not yet live. In the meantime, the practical rule is straightforward: work out your weekly winter consumption from your delivery records, treat a quarter tank as empty, and order before you reach it.
No reliable gauge on your tank? An electronic one with a low-level alarm costs a fraction of a blocked pump.
Questions we get asked about this
How much oil does a house use?
It varies enormously with insulation, occupancy, thermostat settings and boiler efficiency. Your own delivery history is a far better guide than any figure based on property size.
When should I reorder?
At a quarter tank, and earlier in winter. The reserve keeps the sludge layer at the bottom of the tank undisturbed and gives you margin when delivery lead times extend.
Why does running the tank low cause problems?
It draws the settled layer of water and sediment from the tank floor into your supply line. It blocks filters, can reach the nozzle and occasionally damages the pump – and the consequences appear over the following weeks.
Are electronic tank gauges worth it?
If you have ever run low, yes. They are inexpensive, they warn you before it matters, and many will alert you to a sudden drop – which is the usual signature of theft.
Does the tool tell me the oil price?
No. We have no licensed source for price data and will not publish figures we cannot stand behind. It tells you how long what you have will last.
Is the tool available now?
Not yet. The rule in the meantime is simple: work out your weekly winter consumption from your delivery records and treat a quarter tank as empty.
Need this doing?
Call and describe the problem — you will speak to an engineer, not a call centre. Written quotes, no estimates over the phone.