About OffGrid Sizer

OffGrid Sizer publishes free, no-signup calculators for people planning backup power, solar, battery banks and low-voltage DC wiring: homeowners preparing for outages, RV and van owners, cabin builders and campers.

How the tools are made

Every calculator uses a published formula, and every default value is a stated, editable assumption. The math runs in your browser. Each page shows its formula and a worked example, and the full assumptions are on the methodology page. The calculators are written and maintained with the help of AI and automated tests. Every formula is checked against reference values before a page is published.

How the site is funded

Some pages link to products or quote services through affiliate links. If you buy through one, we may earn a commission at no extra cost to you. Affiliate relationships never change a calculator's math or recommendations. See the affiliate disclosure. The site may also show display advertising.

Not professional advice

Results are planning estimates. Electrical work on home wiring, transfer switches and permanent battery systems should be done or inspected by a licensed electrician under local code.