About BackupSizer

BackupSizer exists because every backup-power sizing tool on the internet is a sales funnel. Generac's sizer sells Generac. Retailer calculators sell their SKUs. This site sells nothing of its own — it computes what your house needs and shows the three honest ways to meet it, with the math on the table.

It is built and maintained by The BackupSizer Team. BackupSizer is built and maintained by a software engineer who got tired of every generator sizing tool selling a brand. The load math here follows the NEC 220.83 optional method, and every constant in the calculator is published with its source on the methodology page.

I don't install generators and I don't claim to. What I do is read spec sheets, verify numbers against primary sources, and put the sizing method in public where you can check it — every formula and every source is on the methodology page. When the honest answer is "a battery can't do this" or "you don't need the big unit," the tool says so, because a sizing site you can't trust is worthless.

How the site makes money

Some product and quote links are affiliate links. If you buy a battery system or request installer quotes through them, the vendor pays a commission. It costs you nothing and it never touches the math — recommendations come from the load calculation, and plenty of results pages recommend paths that pay us nothing (there is no Generac affiliate program, and we recommend standby generators constantly). Details on the disclosure page.

Spot an error? A fresher spec sheet? Tell me — corrections ship fast and get noted.