Terms of use

What this site is

Home Energy Math is an independent publisher of financial models for residential solar, battery storage and heat pumps in the United States. We do not sell, install, finance, lease or service any equipment, and we are not a broker, marketplace or contractor. Using this site creates no business relationship between us beyond your use of the pages.

Estimates, not advice

Every figure here is a modelled estimate produced from published data and the stated assumptions. It is general information, not tax, legal, engineering or financial advice, and it is not a quote, an offer or a guarantee of any outcome.

The model can be wrong, and the ways it can be wrong are listed on the methodology page rather than buried. Real results depend on your roof orientation and shading, your specific utility tariff, your tax position, equipment choices, installer pricing and future policy — several of which we cannot see and none of which we control. Confirm anything that matters with a licensed professional and with your own utility before you sign a contract.

Data sources and accuracy

Sunlight figures come from NREL PVWatts v8; electricity rates from EIA; state programmes from the administering agencies. We check what we publish and we mark data we have not finished verifying, but public datasets carry errors and programmes change without notice. We make no warranty that any figure is current, complete or accurate, and we accept no liability for decisions taken in reliance on one. If you spot an error, tell us — see the about page.

Third-party links

Links to other companies, some of them paid affiliate links, are described on our disclosure page. We do not control those sites and are not responsible for their content, their pricing, their privacy practices or how they treat you as a customer. A link is not an endorsement of any particular company.

Acceptable use

Use the site for your own purposes, personal or commercial. Do not attempt to disrupt it, scrape it at a volume that degrades it for others, or present our figures as your own work without attribution. Our text and the model itself remain ours.

Limitation of liability

The site is provided as is, without warranties of any kind. To the fullest extent the law allows, we are not liable for any loss arising from your use of it or reliance on its figures, including financial loss on an energy purchase. Some jurisdictions do not allow certain exclusions, in which case they apply only to the extent permitted.

Changes

We may update these terms; the date above tracks that. Continued use after a change means you accept the revised version.