System sizing

System size by household size

Enter how many people live in your home. Get an instant estimate before you've even pulled up a utility bill.

Your numbers

1 Project details Optional
Shown on your exported report. Leave blank to skip.
2 Who lives there
Age 18 and up, living there full-time.
Kids typically use less energy per person than adults.
3 Where and how you live
A home that's occupied all day runs HVAC and devices more.
Heating and cooling load varies more by region than almost anything else.
4 Appliances that add real load

How it works

A precise estimate from who lives there

Step 1

Count adults and children separately

Adults and children use meaningfully different amounts of energy on average, so this tool asks for each separately instead of one flat headcount. It works even before you've pulled up a utility bill.

Step 2

Add climate, occupancy, and real appliances

Where you live and whether the home is occupied during the day change usage independently of headcount, and specific appliances like a pool or electric water heater add real, countable load. See the fixed-size home tools instead if square footage matters more to you than headcount.

Step 3

Confirm with a real bill once you have one

This is still a household-profile estimate, not a reading off your own meter. Once you have a bill, the monthly usage tool or annual usage tool work from your real numbers instead.

Understanding this household-based estimate

What a typical household needs

A 2-adult, 2-child household with a mixed daily schedule in a moderate climate needs roughly 6.4 kW, around 16 panels. Add a hot climate and a pool and that same household jumps to about 9.6 kW, a real difference driven entirely by climate and one appliance, not headcount.

Why adults and children are counted separately

This estimate adds roughly 140 kWh a month per adult and 70 kWh per child on top of a 250 kWh household base, since children typically account for less device and appliance usage than a full-time adult resident. A flat per-person number would overstate usage for families with young kids, though EIA's own per-capita consumption data confirms household size is a real driver of total usage even without breaking out the adult-versus-child split this tool applies.

Climate and occupancy move independently of headcount

A hot climate adds roughly 25% to the baseline and a cold climate about 20%, while a mild climate subtracts around 15%, entirely separate from how many people live there. A household that's home most days also runs HVAC and devices longer than one that's away on weekdays, which is why this tool asks both as their own inputs.

Specific appliances add real, countable load

An electric water heater adds roughly 300 kWh a month, a pool or hot tub about 200, an electric dryer about 75, and a daily home office about 40. These are concrete additions this tool can count directly, instead of folding them into a vague per-person average that either misses them entirely or overstates usage for households without them. The Energy Information Administration's 2020 Residential Energy Consumption Survey publishes the underlying household energy use data by appliance and end use.

What this estimate won't capture

Home size still matters independently of who lives there. A large home with 2 residents can use more electricity than a small home with 4, which is why the fixed-size home tools exist as a different starting point when square footage is the more relevant factor for you.

What to do with this number next

Household size is what drives the usage behind this number, so take your estimated system size to the payback period calculator to see what it might save you over time, or to the federal ITC calculator to check what programs apply to a system of this size.

Questions

Frequently asked

A 2-adult, 2-child household with a mixed daily schedule in a moderate climate needs roughly 6.4 kW, around 16 standard 400-watt panels. A hot climate with a pool pushes that same household to about 9.6 kW.

This estimate adds roughly 140 kWh a month per adult and 70 kWh per child on top of a 250 kWh household base, since children typically account for less device and appliance usage than a full-time adult resident. A flat per-person number would overstate usage for families with young kids.

Often yes. A hot climate adds roughly 25% to the baseline and a cold climate about 20%, while being home most days versus away on weekdays changes how long HVAC and devices actually run, both independent of how many people live there.

An electric water heater adds roughly 300 kWh a month, a pool or hot tub about 200, an electric dryer about 75, and a daily home office about 40. This tool counts each one you check directly rather than folding them into a generic average.

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