What a full conversion actually needs
The baseline for a typical conversion
A 2,000 sq ft home with a 4-person household in a moderate climate converting heating, water heating, and appliances all at once needs about 6.8 kW. The same home in a cold climate needs closer to 8.4 kW, a real jump driven almost entirely by climate's effect on space heating.
Space heating is the largest single piece by far
In a 2,000 sq ft moderate-climate home, heat pump space heating alone accounts for roughly 70% of the total conversion load, with water heating, dryer, and cooking making up the rest. That lines up with the broader pattern in household energy data, where heating and cooling represent the single largest category of home energy use, well ahead of water heating, drying, or cooking individually. The Energy Information Administration's 2020 Residential Energy Consumption Survey breaks down that split by end use. Getting the heating estimate right matters more than any other single input in this calculation.
Why plan the whole conversion at once
Many conversions happen as a single planned project, often tied to one rebate application or one contractor visit, so sizing solar for the whole eventual load at once avoids undersizing a system that gets asked to cover more than planned later. Expanding a system after the fact means a second round of labor, permitting, and interconnection paperwork. Doing the work together in one project usually saves money through shared labor and a single permit, compared to doing each piece separately. The Department of Energy's home upgrades guide covers the sequence and the incentives that apply when electrifying a whole home.
How this differs from converting one appliance at a time
This tool sizes the full combined load of heating, water heating, and appliances together. The heat pump addition tool and water heater addition tool size just one piece each, useful if you're only converting a single appliance right now rather than planning the whole switch. A full conversion also changes your whole energy bill, not just the solar side, and the annual bill reduction estimator works out what the switch saves across heating, water, and appliances together.
What to do with this number next
Take your estimated system size to the federal ITC calculator to check what programs apply to a full conversion, since many utilities and states offer combined incentives for whole-home electrification projects.