The right size.
For your home.

Generator, cooling, hot water or solar.
Find your starting size, with the working shown.

Free to use. No signup. A planning range, with assumptions you can adjust.

A bright home with a garden and outdoor cooling unit

What are you sizing?

Start with the job your equipment needs to do.

Backup power equipment in a residential setting

Backup power

Keep the loads that matter running.

Solar power equipment in a residential setting

Solar power

Turn your electricity use into a panel count.

House exterior and HVAC equipment

A starting point.
With the working shown.

You should be able to see where the number came from.

  1. Your home

    Area, insulation and the equipment you actually use.

  2. Your location

    County climate zones and a representative solar weather snapshot.

  3. Your assumptions

    Every calculation shows its inputs, range and limits.

See how the models work

Buy the right size once.

Make your next conversation with a contractor more useful.

Find my starting size