Editorial policy and corrections

Apply a month too late or plan with a grant rate that no longer applies and the money is gone for good. So this page says where every figure comes from and what happens when one is wrong.

Responsibility

Content and calculators are the responsibility of Radif Partners. Contact: kontakt@heizrechnen.de.

Primary sources only

Federal Gazette and the promotional bank (KfW): the federal efficient buildings funding guideline, information sheets, product pages with worked examples;
Federal Law Gazette and gesetze-im-internet.de: Building Modernisation Act, Fuel Emissions Trading Act, CO₂ Cost Allocation Act, Heat Planning Act, Income Tax Act;
German Bundestag: where bills stand;
Federal Statistical Office, Federal Network Agency, European Commission, German Weather Service, Fraunhofer ISE: energy prices, degree days and measured performance factors.

Manufacturers, installers, comparison portals and press reports are not sources, even when they rank first in search results.

Announcements and bills

What an authority announces without a fixed date or rule, and what the Bundestag has passed but not yet promulgated, is labelled and dated as such. The calculator visibly flags any result that depends on such a rule as uncertain.

Checks before every release

The bank’s worked examples, every step of the bonuses and caps, the CO₂ factors and the CO₂ split tier table run as automated tests. A value that differs stops the release.

Rhythm

Full review at least every 12 months, plus on each date the guideline changes, after new price data and after every change in the law.

Handling errors

Check against the primary source.
Fix the parameter file or the calculator and add a test.
New date on every page; a correction of substance is noted on the page.

Independence

No money from manufacturers, installers, energy suppliers or brokers. No product recommendations, no quote form.

See also how we calculate. Version: 2026-10-19.