HEATING FAQ
Questions worth answering.
Clear answers to common questions about heating load,
fuel consumption, energy units and calculator accuracy.
How much heating power do I need per square metre?
There is no universal heating-power requirement per square metre.
A well-insulated building in a mild climate may need substantially
less heating power than a draughty building in a cold region.
This calculator uses illustrative base factors of 35, 55,
80 and 110 W/m² for its insulation categories, then applies
climate, height and temperature adjustments. These factors
are not substitutes for a detailed building heat-loss assessment.
How do I calculate how much firewood I need for winter?
Estimate the useful heating energy needed over your chosen period,
then divide by the energy per kilogram of wood multiplied by
your stove or boiler efficiency. For example, at 4.0 kWh/kg
and 75% efficiency, each kilogram provides an estimated
3.0 kWh of useful heat. To supply 990 kWh, you would
calculate 990 ÷ 3 = 330 kg. Real consumption varies
with moisture, combustion conditions and building demand.
How much natural gas does it take to heat a house?
Natural gas consumption depends on building heat demand,
fuel energy content and heating-system efficiency.
Using this calculator's defaults of 10.5 kWh/m³ and
92% efficiency, an illustrative 990 kWh useful heat
demand would require about 102.5 m³ of natural gas.
Your supplier's calorific value, local volume reference
conditions and boiler performance may change that estimate.
What is the difference between kW, kWh and BTU?
kW measures power, or the rate of energy transfer.
kWh measures energy delivered or consumed over time.
BTU (British thermal unit) is another energy unit,
while BTU per hour measures power.
Approximately 1 kWh equals 3,412 BTU,
and 1 kW equals 3,412 BTU per hour.
What does heating system efficiency mean?
System efficiency compares useful heat output with
fuel energy input. In a simplified example, a
boiler at 80% efficiency delivers 8 kWh of useful
heat from 10 kWh of fuel energy. Be aware that
appliance ratings can use different test conditions
and gross or net heating-value conventions.
Why can a heat pump have a COP greater than 1?
A heat pump moves heat rather than generating all
its heat directly from electricity. A COP of 3
means approximately 3 kWh of useful heat is delivered
for every 1 kWh of electricity consumed under the
relevant conditions. COP varies with temperatures and
operation. Seasonal COP or seasonal performance factor
is more suitable for longer-term consumption estimates.
Does a bigger house always need more heating?
With everything else equal, a larger heated area
generally increases heating demand. But size alone
is insufficient. Insulation, glazing, air leakage,
building geometry and climate can cause a smaller
building to need more heating power than a larger,
better-performing one.
Can I use this calculator to estimate monthly consumption?
Yes. Enter the number of heating days, daily operating
hours and an average load percentage to model a
monthly or other selected heating period. The tool
estimates total useful heat, fuel quantity and average
daily consumption. It does not forecast the actual
weather for that period.
Is wood heating more efficient than gas or electric heating?
Efficiency depends on the specific appliance and
operating conditions, not merely the fuel type.
A modern wood-pellet boiler can differ considerably
from an open fireplace. Direct electric resistance
heating converts approximately all purchased electricity
into heat at the point of use, while heat pumps can
supply more than one unit of heat per unit of
electricity. Efficiency alone does not determine
running costs or environmental impact.
Can this calculator tell me which heating fuel is cheapest?
Not directly. The calculator compares energy and
fuel quantities, not live local prices. To compare
costs, multiply each estimated fuel quantity by
the matching local price per kg, litre, m³ or kWh.
Consider standing charges, maintenance and system
installation costs separately where relevant.
How accurate is the heating fuel calculator?
The arithmetic follows the displayed equations,
but the accuracy of the real-world estimate depends
on the assumptions supplied. A floor-area model
cannot measure your actual building heat loss,
future weather, fuel condition or appliance performance.
Use it for early planning and scenario comparisons.
For equipment sizing, request a detailed room-by-room
heat-loss calculation from a qualified professional.