What will this household spend in total on home energy, including any installation costs, from 2027 through 2036?

Outcome Summary Installing the heat pump next year costs an estimated €53,330 at the median over the 2027–2036 window, structurally outperforming the €61,500 median cost of running the gas boiler to failure. Crucially, the proactive installation eliminates roughly €17,000 of right-tail financial risk. Initial baseline parameters—a 142 sqm house requiring ~18,500–19,000 kWh/a of useful heat, a heavily depreciated 2004 boiler, and the July 2026 GEG/BEG regulatory realities—are fully established context. The core divergence between these alternatives rests entirely on replacing variable future regulatory liabilities with fixed, near-term, and highly subsidized capital.

The Heat Pump Mechanism (Branch A) Executing the heat pump installation in 2027 secures the current BEG heating grant before further scheduled degradation 2 sources. Translating the €34,200 quote into a net capital outlay of roughly €21,000–€23,000 (locking in a ~42–46% grant on a €27,250–€28,000 eligible cost cap) kfw.de sharply front-loads the decade's expenditure. Operating costs then immediately transition to ~6,000–6,300 kWh/yr of dedicated heat-pump electricity at 20–26 ct/kWh 2 sources. Because ~40% of the total decade spend is contractually fixed on day one and thoroughly decoupled from fossil carbon markets, this branch yields a much tighter overall distribution (€43,330 to €67,000), driven only by marginal variations in seasonal performance factors (SPF ~2.6–4.0) ise.fraunhofer.de and baseline electricity path drift.

The Gas Boiler Mechanism (Branch B) Retaining the 2004 boiler keeps near-term cash but buys escalating, compounded operational risks. Maintaining the fossil status quo guarantees pure exposure to the EU ETS2 carbon market (widely projected at €120–€150/t by 2030) 2 sources, the new supplier-level Grüngasquote starting in 2028 2 sources, and structurally multiplying gas network charges as the regional customer base defects to electric heating 2 sources. A baseline decade of sustained gas and standard household electricity outlays inherently floors the minimum spend around €45,170, leaving no realistic path to high savings even in perfectly benign macroeconomic scenarios.

The Forced-Replacement Leap The definitive liability in the waiting branch is the 85–90% probability of boiler failure mid-decade. Because the 2026 Gebäudemodernisierungsgesetz removed the strict 65% renewables rule, a like-for-like emergency gas swap is legal but mandates compliance with the escalating "Bio-Treppe" (10% green fuel in 2029, 30% by 2035) 2 sources. Alternatively, a forced mid-decade heat pump transition would occur under severely depleted subsidies—the critical speed bonus vanishes entirely after August 2028 and the eligible cap aggressively shrinks kfw.de. This compounding penalty of emergency capex, rising carbon levies, and network fees drives the massive €84,330 upper tail, highlighting why deferring action creates asymmetrical downside.