🌡️ Thermostat Savings Calculator
Estimate the savings from adjusting your thermostat setting, using a commonly cited rule of thumb of about 1% savings per degree adjusted per day (varies by home and climate).
How the estimate works
Three inputs: your current bill, how many degrees you are changing the thermostat by, and the saving you expect per degree. They multiply:
saving = bill x degrees x (percent per degree / 100)The percent-per-degree box defaults to 1 and accepts anything up to 5, because the honest answer to what one degree is worth depends on your house, and hard-coding a single figure would hide that.
Choosing the percentage honestly
The widely quoted rule of thumb is 1 to 3% of heating cost per degree Fahrenheit, over an eight-hour setback. Where you sit in that range depends on things the calculator cannot see:
- Insulation. A well-insulated house loses heat slowly, so a lower thermostat saves less than the rule suggests. A draughty one saves more.
- Climate. The saving comes from the gap between inside and outside. The same one-degree change is worth far more in a cold winter than a mild one.
- How long the setback lasts. A degree lower for eight hours while you sleep is not a degree lower all day.
- What is on the bill. Standing charges, water heating, lighting and appliances do not respond to the thermostat at all.
Where the real savings are
Setback beats set-point. Lowering the temperature while the house is empty or everyone is asleep saves more than shaving a degree off around the clock, and nobody has to feel it. A programmable or smart thermostat mostly earns its keep by making that automatic rather than by being clever.
Two persistent myths are worth retiring:
- Letting the house cool does not cost more to reheat. A cooler house loses heat more slowly, and the energy saved during the setback exceeds the recovery cost. The exception is a heat pump, which is less efficient when asked to recover a large gap quickly.
- Turning the thermostat far up does not heat faster. Most systems have one output. Setting 30 instead of 21 only makes it run past the point you wanted.
Frequently asked questions
How much does turning the thermostat down 1 degree save?
Commonly quoted at 1 to 3% of heating cost per degree over an eight-hour setback. Use the low end for a well-insulated house in a mild climate and the high end for a draughty one in a cold winter.
Should I use my whole bill as the input?
Only if the bill is heating alone. If it also covers water heating, lighting and appliances, enter the heating share, or the saving will be overstated.
Is it cheaper to leave the heating on low all day?
No, for most systems. A house that is allowed to cool loses less heat while you are out than one held at temperature, and reheating costs less than the loss avoided. Heat pumps are the exception and prefer steadier temperatures.
Does turning it up higher heat the room faster?
No. Most heating systems have a single output level, so a higher setting changes only when it stops, not how quickly it warms the room.
Will a smart thermostat save more than this?
It saves the same energy per degree; what it changes is consistency. Its value is in applying setbacks reliably rather than in any efficiency the thermostat itself provides.