"What's cheapest?" - This is the No. 1 question every homeowner asks. The answer isn't obvious, because you can't simply compare sale prices (€/litre or c€/kWh). You must factor in the efficiency of each machine.
Let's "translate" each fuel into cost per thermal kWh - that is, how much you pay for each unit of actual heat that reaches your living room.
In Greece, the five most common fuels (or energy sources) for building heating each have a different purchase price and different efficiency.
The most traditional heating method in Greece. Price ranges €1.10–1.40/litre, but depends directly on international oil prices and seasonality. A modern condensing boiler achieves 92-95% efficiency, while an old atmospheric one only 80-85%.
Pipeline network - no storage space needed. Price ranges €0.05–0.08/kWh (depending on supplier and consumption). A gas condensing boiler reaches 95-98% efficiency - practically every cubic metre becomes heat with almost zero losses.
Biofuel from compressed sawdust. Price €0.30–0.40/kg, with energy content of about 4.8 kWh/kg. A pellet boiler achieves 85-92% efficiency. Requires storage space (silo) and regular cleaning - but price stays stable, independent of oil markets.
Convectors, panels, fan heaters. Efficiency 100% (each kWh of electricity becomes exactly 1 kWh of heat). But Greece's electricity price (€0.12–0.20/kWh) makes it the second most expensive heating source.
The key formula is simple: Cost per thermal kWh = Fuel price / (Energy content × Efficiency). This levels the playing field - every energy source measured by the same yardstick.
At €1.20/litre with energy content 10.25 kWh/litre, in a modern boiler (93%): 1.20 / (10.25 × 0.93) = ~€0.126/kWh . In an old boiler (82%), it rises to €0.143/kWh.
At €0.06/kWh gross with boiler efficiency 96%: 0.06 / 0.96 = ~€0.063/kWh . Natural gas remains the cheapest fossil fuel solution.
At €0.35/kg with energy content 4.8 kWh/kg, in 88% boiler: 0.35 / (4.8 × 0.88) = ~€0.083/kWh. Price stability year after year.
Here's where the magic happens. At electricity price €0.15/kWh with annual COP 3.8: 0.15 / 3.8 = ~€0.039/kWh . The heat pump is the cheapest heating source - 3-4× cheaper than oil!
Efficiency is the hidden multiplier. A cheap fuel with low efficiency can end up more expensive than a "costly" fuel in a high-efficiency machine.
Fossil fuels (oil, gas) burn in a boiler. For every 100 kWh of energy in the fuel, only 80-98 kWh become heat - the rest escapes through the flue. Condensing boilers recover some of this, reaching 98%.
The heat pump doesn't "burn" - it transfers heat from the air. For every 1 kWh of electricity, it delivers 3.0 – 5.0 kWh of heat. Efficiency 300-500%! That's why it's by far the cheapest heat source, despite more expensive electricity.
Convectors, electric radiators, panels. Each kWh of electricity gives exactly 1 kWh of heat . This sounds "perfect", but compared to the heat pump (which gives 3.5 kWh of heat with the same electricity), it proves 3.5× more expensive.
Many compare "€/litre of oil vs c€/kWh of electricity" and reach wrong conclusions. The only correct comparison is: € per thermal kWh. Only by factoring in efficiency will you see the real picture.
The mathematical truth is indisputable: the heat pump produces the cheapest thermal kWh in every scenario. Even if electricity prices rise 20%, it remains cheaper than oil.
1st Heat Pump (~€0.04/kWh), 2nd Natural Gas (~€0.06), 3rd Pellet (~€0.08), 4th Oil (~€0.13), 5th Electric resistance (~€0.15). The heat pump costs 3× less than oil!
100 m² home, annual need 10,000 kWh . Oil: €1,300/year. Gas: €630/year. Heat pump: ~€400/year. Savings of €900/year if you replace oil with a heat pump!
Don't forget: for oil add annual boiler service (€100-200) and possible repairs. Heat pumps need only filter cleaning - minimal maintenance with maximum performance.
If you pay over €1,000/year for oil, replacing with a heat pump pays back in 5-7 years without subsidy. With the "Exoikonomo" programme, in just 2-3 years.
💡 Don't compare fuel prices - compare cost per thermal kWh. Efficiency makes all the difference!
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