How do you use this tool?
- Pick the fuel or heat source: natural gas, heating oil, wood pellets, heat pump, district heat or direct electric.
- Pick the building efficiency class: very inefficient ≈ 220 kWh/m²·a, standard ≈ 130, energy-efficient ≈ 70 or passive house ≈ 30 — or enter a custom value.
- Enter the living area in m² and decide whether to include domestic hot water (+20 %).
- Optional: override the 2026 default price per kWh — for heat pumps additionally pick the JAZ (annual coefficient of performance) between 2.5 and 4.5.
- Output: yearly and monthly heating cost, kWh consumption, CO₂ emissions, the BEHG share of heating cost and a fuel-switch comparison card for all six classes — copy-paste-ready.
What does the heating cost calculator do?
The calculator estimates your yearly and monthly heating costs from four input parameters: fuel or heat source, building efficiency class, living area and the hot-water toggle. Six fuel classes are computed in parallel — natural gas, heating oil, wood pellets, heat pump, district heat and direct electric. Outputs are yearly and monthly cost in euro, the energy consumption in kWh, the CO₂ emissions in kg per year and the BEHG share of heating cost.
Three differentiators no other online calculator combines this cleanly: a CO₂ price slider with the BEHG trajectory from 2026 to 2030+ (no competitor offers an interactive sensitivity to the carbon-price path), a JAZ slider for the heat pump with a realistic 2.5 to 4.5 range from field studies (instead of a fixed 3.5 value that flatters the system), and a transparent assumptions box (show-not-hide) that surfaces every assumption parameter — kWh/m²·a, €/kWh, η or JAZ, CO₂ factor, hot-water status — directly under the result.
All math runs locally in your browser. No upload, no tracking, no data leaves your device. Pure-client matches the sensitive nature of retrofit and subsidy-application data.
How is the heating cost computed?
The model follows a simple energy balance that most competitor calculators hide behind their UI:
Q_useful = livingArea × kWh/m²·a × (1 + hot-water-factor?)
Q_input = Q_useful / systemEfficiency
yearlyCost = Q_input × pricePerKwh
CO₂_kg = Q_input × co2KgPerKwh
BEHG_share = CO₂_kg × co2PriceEurPerTon / 1000Where:
- Q_useful = useful heat demand (kWh/year) — what needs to arrive as usable heat in the building.
- kWh/m²·a = typical final-energy demand for the efficiency class (very inefficient ≈ 220, standard ≈ 130, energy-efficient ≈ 70, passive house ≈ 30).
- hot-water-factor = +20 % per DIN V 18599 convention when hot-water is included.
- systemEfficiency = condensing boiler η ≈ 0.92, pellet boiler η ≈ 0.88, district heat η = 1.0, heat-pump JAZ (annual coefficient of performance 2.5 to 4.5).
- pricePerKwh = 2026 default or your specific tariff price (gas 0.10 €/kWh, oil 0.085 €/kWh, pellets 0.060 €/kWh, heat-pump electricity 0.40 €/kWh, …).
- co2KgPerKwh = emission factor per fuel in kg CO₂ per kWh final energy (gas 0.202, oil 0.266, pellets 0.025, electricity grid mix 0.380, district heat 0.175).
- co2PriceEurPerTon = BEHG value in € per ton (2026: 65 €/t fixed, from 2027 EU ETS-2 market phase, slider up to 200 €/t).
Worked example: 120 m² standard building (130 kWh/m²·a), natural gas, hot water included.
- Q_useful = 120 × 130 × 1.2 = 18,720 kWh/year
- Q_input = 18,720 / 0.92 = ~20,350 kWh/year
- yearlyCost = 20,350 × 0.10 € = ~2,035 €
- CO₂_kg = 20,350 × 0.202 = ~4,110 kg
- BEHG_share = 4,110 × 65 / 1,000 = ~267 €
The same building with a heat pump at JAZ 3.0 and 0.40 €/kWh heat-pump electricity: Q_input = 18,720 / 3.0 = ~6,240 kWh of electricity, yearlyCost = ~2,496 €. More expensive on the pure fuel side than gas — because of high electricity prices — but the heat pump benefits massively from subsidies and lower CO₂ share.
Which fuel classes does the tool know?
Six classes with 2026 default prices, all overrideable:
| Fuel | Default price 2026 | Efficiency / JAZ | CO₂ factor (kg/kWh) |
|---|---|---|---|
| Natural gas | 0.10 €/kWh | η ≈ 0.92 (condensing) | 0.202 |
| Heating oil EL | 0.085 €/kWh (~0.85 €/L) | η ≈ 0.92 | 0.266 |
| Wood pellets | 0.060 €/kWh (~0.30 €/kg) | η ≈ 0.88 | 0.025 |
| Heat pump | 0.40 €/kWh electricity | JAZ 2.5–4.5 (default 3.0) | 0.380 (grid mix) |
| District heat | 0.13 €/kWh | η = 1.0 (delivered) | 0.175 (mix) |
| Direct electric | 0.42 €/kWh | η = 1.0 | 0.380 |
Prices are 2026 defaults from typical tariff bands. Every value is overrideable — use your specific contract. Oil and pellets are purchased in litres and kilograms in real life; the tool computes internally in €/kWh and uses a calorific-value conversion (10 kWh/L for oil, 5 kWh/kg for pellets).
How does the JAZ slider for heat pumps work?
The annual coefficient of performance (JAZ in German, seasonal performance factor in English) is one of the most important levers for heat-pump economics — and the point where most online calculators cheat by using a lab COP value of 4.0 or 4.5 as the default. Realistic values from Fraunhofer ISE field studies:
| Heat-pump type | Real-world JAZ (median) | Realistic range |
|---|---|---|
| Air-to-water | 3.0–3.1 | 2.5 to 3.5 |
| Ground-source (geothermal) | 4.0–4.2 | 3.8 to 4.5 |
| Water-to-water (groundwater) | 4.2–4.5 | 4.0 to 4.5 |
The slider covers 2.5 to 4.5 — the realistic range for well to very well designed systems. Values below 2.5 indicate hydraulic problems (flow temperature too high, poor radiator heat transfer). Values above 4.5 are lab COP figures, not real annual performance.
The slider directly changes the electricity consumption and the heating cost. JAZ 2.5 instead of 3.5 raises costs by ~40 % — realism is not optional.
How does the CO₂ price slider work?
The German Brennstoffemissionshandelsgesetz (BEHG) has applied a fixed carbon price to fossil fuels since 2021. Trajectory:
| Year | CO₂ price | Phase |
|---|---|---|
| 2024 | 45 €/t | Fixed price |
| 2025 | 55 €/t | Fixed price |
| 2026 | 65 €/t | Fixed price (slider default) |
| 2027 | ~70 €/t (last fixed-price year) | Fixed price |
| 2028+ | Market-determined | EU ETS-2 |
| 2030 (scenarios) | up to 200 €/t | EU ETS-2 |
Worked example: an oil household at 23,000 kWh of final energy per year pays a CO₂ share of about 400 € at 65 €/t (≈ 17.5 ct per litre of heating oil). Move the slider to 150 €/t (an EU ETS-2 mid-scenario for 2029) and the share jumps to about 920 € — that shifts fuel economics against fossil sources massively.
The slider shows this sensitivity directly under the big-number card. No competitor calculator does this interactively.
What does the tool NOT calculate?
Deliberately out of scope to keep scope and liability clean:
- No manufacturer model picker. Heating-system models change quarterly, brand comparison would be an affiliate magnet and vendor bias.
- No BAFA/KfW subsidy application logic. Subsidy rules change quarterly, wrong quota numbers would be a liability risk. Static hints in the text instead, with a pointer to a BAFA on-site consultation.
- No heating bill audit. A separate tool world with consumption and allocation logic.
- No lead funnel. We do not link to energy providers or heating contractors and we collect no contact data. AdSense instead of affiliate.
- No 10-year forecast. Model assumptions beyond 2028 are speculative (EU ETS-2 market price path is unknown).
- No smart-meter integration / live consumption data. Breaks the pure-client principle.
- No heating-bill PDF upload analysis. A separate file tool, if at all — also without server roundtrip.
Which construction tools are related?
For full retrofit packages:
- Insulation calculator — wall, roof and floor insulation with U-value/R-value conversion and GEG 2024 compliance check.
- Window U-value calculator — Uw per DIN EN ISO 10077-1 with GEG / KfW / passive-house tiers.
- Screed calculator — layer thicknesses for heating modernisation (underfloor-heating compatibility).
- Masonry calculator — material and mortar quantities for new builds and extensions.
- Wall paint calculator — interior finishing after the heating swap.
Phase-B candidate: a separate heat-pump sizing calculator with heating-load computation — depending on search-volume data. Once Google Search Console shows enough heat-pump queries over 6 weeks, we will ship it. Until then the heating cost calculator covers the fuel-cost side.
What else do people ask about heating costs?
The frontmatter of this page contains eight FAQ entries with schema.org/FAQPage markup, sourced from top Google “People also ask” patterns for heating-cost topics. The answers address the question in the first 10 words — voice-search optimised for smart speakers and AI search assistants.
Important note: The tool gives an estimate based on typical class-average final-energy demand and 2026 default fuel prices. Real heating costs vary by ±20 % depending on local tariffs, usage patterns and system condition. For a concrete savings, subsidy or fuel-switch recommendation an independent energy advisor (BAFA on-site consultation in Germany) is required.
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