System builder
Work out what a system has to do, then choose the battery, inverter and panels that do it. It is a planning draft, not a quote: it says plainly what it does not know. It is not an electrical design or a code check: confirm string layouts, wire sizes and protection against the manufacturer installation manuals with a qualified, licensed installer before you buy or build.
Needs
List what the system has to run and for how long. Everything after this screen is chosen to satisfy the three targets at the bottom, and you can change them by hand at any point.
What will it run?
Start from an example and edit it, or add appliances one at a time. Nothing is filled in for you until you press something.
- Just the essentials
- Fridge, freezer, lights, internet, chargers and a furnace blower.
- An off-grid cabin
- The essentials plus a water pump, a heat pump and a small kitchen.
- A whole house
- A full kitchen, laundry, water heating and air conditioning.
Add what it has to run
The watts and hours above are typical planning figures, not measurements and not catalog facts. Replace them with what the label on your own equipment says.
Or use a measured figure
Import usage CSV
Your file stays in this tab. It is not uploaded or saved. Only planning targets you apply enter the shareable build link.
Emporia and CSV format
Unzip the export, then choose one comma-separated CSV with a header row. Emporia 1SEC, 1MIN and 15MIN files use kW; 1H and 1DAY files use kWh. Timestamps must mark interval starts. Missing, duplicate, mixed-offset and negative readings are rejected.
How long must it last without sun?
Will you fit solar panels?
Sun hours are the equivalent hours of full-rated sunshine a day, which is not the same as hours of daylight. We hold no solar resource data for your address and are not going to invent a figure for it: look yours up in NLR’s PVWatts and type it in. For scale, cloudy northern winter is about 2.5, much of the United States, year round is about 4, desert southwest is about 5.5. Sizing for the worst month halves the figure, which is the usual approximation for a mid-latitude December and no substitute for the real monthly number.
Your targets
Nothing yet. Add an appliance above, or set the three targets by hand.
Show the arithmetic
- Energy through a day
- Each appliance: watts × how many × hours on × share of that time it draws = 0 kWh
- Nameplate storage to buy
- 0 kWh × 1 day × 1.2 margin ÷ 80% usable = 0 kWh
- Continuous output
- 0 kW connected × 1.25 = 0 kW
- Surge to survive
- 0 kW connected × 1.2; nothing listed has a motor start = 0 kW
- Solar array
- 0 kWh ÷ 4 sun hours ÷ 80% delivered × 1.2 = 0 kW
These margins are planning conventions, not guarantees, and not facts about any product here. A real installation is sized by someone who has seen the site.
Set the targets by hand instead
Or start from a finished draft
Each of these ranks the battery across the whole catalog and then picks an inverter and panels to fit it. Only the battery is ranked. A button is off when the catalog holds nothing it could rank that way. Each needs your targets above first.