Terms of use

What this site is

A free reference with worksheets that model household battery economics from published rate, tax and hardware data. Using it means accepting these terms. If you do not, the remedy is not to use it.

What the output is not

Not a quote, not an offer, and not a promise of savings. The figures are projections from inputs you supply and constants we publish with their sources; they cannot account for your electrical service, your roof, your local permitting, your tax position or the weather. Your actual result will differ, sometimes materially.

Nothing here is financial, tax, legal or engineering advice. In particular, the pages discussing tax credits describe published rules as we retrieved them and are not a substitute for a professional looking at your own return. Decisions about spending money should be taken with somebody qualified and licensed for your circumstances.

Accuracy and currency

Every constant carries a source and a retrieval date, and the methodology page lists them all. Tariffs are refiled, tax provisions lapse and datasheets are revised, so a figure correct on its retrieval date may not be correct when you read it. Check anything load-bearing against its source before acting on it. We correct defects when they are reported but do not warrant that the site is error-free or continuously current.

No relationship with the vendors named

Manufacturer and utility names appear because their published specifications and tariffs are the data this site works from. No endorsement in either direction is implied, no commercial relationship exists with any of them, and none has reviewed or approved anything here. Trade marks belong to their owners.

Using what you find here

Read it, print it, run the numbers, take a screenshot to an installer. That is what it is for. Do not republish the text or the data tables as your own work, and do not scrape the site to build a competing product. Linking to it is welcome and needs no permission.

Availability

The site is offered as it is, without any warranty of availability, fitness or uninterrupted operation. It may change or disappear without notice. To the fullest extent the law allows, the publisher is not liable for any loss arising from use of the site or reliance on anything in it, including any decision to buy or not buy equipment.

Governing law

These terms are governed by the laws of the State of California, without regard to conflict-of-law rules. Nothing here limits any right you have that cannot be limited by law where you live.

Changes

These terms may be updated; the review date at the top moves when they are. Continuing to use the site after a change means accepting the revised terms. Questions go to the contact page.