System sizing

System size for a detached garage

Enter your garage size and how you use it. Get a solar system sized for a detached garage, whether it needs lighting only or a full workshop with EV charging.

Your numbers

1 Project details Optional
Shown on your exported report. Leave blank to skip.
2 Your garage
A bigger garage typically means more lighting circuits and tool loads.
This single choice matters more than any other input here.
3 Planning ahead

How it works

Sizing for how you actually use the space

Step 1

Start with garage size

A bigger garage typically means more lighting circuits and room for tool use, though usage matters far more than size alone. Size mainly scales the estimate up or down within whatever usage tier you pick. If your garage is attached to the house instead, the fixed-size home tools are the better starting point.

Step 2

Pick the usage tier that matches your plans

Lighting-only, light workshop, and heavy workshop cover very different real-world loads, and this single choice matters more than any other input here. Check EV charging too if you're planning it, since it's often the single biggest addition.

Step 3

Decide between grid-tied and standalone off-grid

A detached garage far from the house is often cheaper to power as its own small standalone system than to trench underground cable to it. See the off-grid panel count calculator for sizing guidance specific to a fully standalone setup.

What a detached garage actually needs

Usage tier matters more than any other input

A medium garage used for light workshop tasks needs about 1.2 kW, around 3 panels. A large garage run as a heavy workshop with EV charging needs closer to 4.0 kW, around 10 panels, a real jump driven almost entirely by how the space gets used, not its size. For a precise number on planned EV charging elsewhere on the property, see the future EV oversizing calculator.

Lighting-only garages need surprisingly little

A garage used only for lighting and an automatic door needs roughly 550 kWh a year, small enough that one or two panels and a small battery can cover it in many cases, especially with efficient LED fixtures. There's no need to oversize a garage that's mostly used for storage.

Grid-tied versus a standalone off-grid system

Trenching underground cable to a detached garage can cost thousands of dollars depending on distance, so a small standalone off-grid system is often cheaper and faster for a garage that was never wired to the house. A garage close to the house with existing wiring is usually simpler to tie into the main system instead. The Department of Energy's homeowner's guide to solar covers the questions to ask before adding solar to an outbuilding.

Why EV charging changes the math so much

Adding EV charging to an otherwise identical garage adds roughly 2,500 kWh a year, usually the single biggest addition to a garage's solar needs, larger than the gap between a light and heavy workshop. That figure is in line with national averages: the Energy Information Administration's household electricity data puts the average US residential customer at 10,791 kWh a year, so a single EV can add roughly a quarter of a typical home's annual use. Planning for it now is typically cheaper than adding capacity later.

What to do with this number next

Once you know your target system size, check the federal ITC calculator for programs that might apply, and use the roof space estimator to confirm the garage roof itself has enough usable area.

Questions

Frequently asked

A medium garage used for light workshop tasks needs about 1.2 kW, around 3 panels. A large garage run as a heavy workshop with EV charging needs closer to 4.0 kW, around 10 panels.

Yes. A garage used only for lighting and an automatic door needs roughly 550 kWh a year, small enough that one or two panels and a small battery can cover it in many cases, especially with efficient LED fixtures.

It depends mostly on distance and existing wiring. Trenching underground cable to a detached garage can run $2,000 to $8,000 or more, so a small standalone off-grid system is often cheaper and faster for a garage that was never wired to the house.

About 2,500 kWh a year for occasional Level 2 charging, which is usually the single biggest addition to a garage's solar needs, larger than the difference between a light and heavy workshop.

Related tools

Keep sizing your system

Solar panel calculator System size by monthly kWh usage System size by electric bill amount System size by square footage, quick estimator Quick 5-minute system size estimator Oversizing for a future EV System size by annual kWh usage All system sizing tools