Solar power for outbuildings: sheds, barns, garages, workshops
Last reviewed · two routes, sized honestly
An outbuilding is the cheapest solar project most properties ever take on — the loads are small, the roof is uncomplicated, and the alternative (a long trench or a drooping extension cord) is easy to beat. The whole decision comes down to one question: how far is the building from the house?
Route one: extend from the house
If the shed or garage sits within a practical trench run, the cleanest answer is usually a subpanel circuit from the house — and if the house has (or gets) an array, the outbuilding simply becomes more load behind the same meter, banking daytime surplus exactly like any other consumption. Trenching cost climbs with distance and terrain: a short open run is a few hundred dollars; rock, pavement, or a hundred-metre pull turn it into a few thousand. Past that line, stop trenching.
The solar-specific version of this route: size the house array for both buildings at once. A workshop's 3-5 kWh a day is one extra panel or two on the main roof — at 3.00/W that is a few hundred dollars of hardware, which no standalone kit will beat. The payback calculator sizes the combined load from a combined bill.
Route two: a micro standalone kit
Beyond trench range — or for seasonal cabins, distant barns, and gates or wells — a small standalone system is the same off-grid architecture at hobby scale:
- Array: 0.4-1.5 kW depending on daily kilowatt-hours (lights-only sheds need the small end; running tools needs the top end). Sizing follows the same 0.8 performance ratio as every page on this site.
- Battery: a 2-5 kWh lithium (LFP) unit covers evenings and motor starting; the autonomy math is on the off-grid guide.
- Inverter: sized to surge, not averages. Compressors and saws draw 2-3× their nameplate for a moment; a 2-3 kW continuous inverter with headroom is the workshop-class answer.
- Mounting: ground mounts and shed roofs are both fine; a small ground array you can re-aim seasonally punches above its rating.
What outbuildings actually use
| Use | Daily energy | Implies |
|---|---|---|
| LED lights + chargers | 0.2-0.5 kWh | 100-200 W panel, small power station |
| Garden/fridge + lights | 1-2 kWh | 400-600 W + 2 kWh battery |
| Weekend workshop (saw, compressor) | 3-5 kWh | 1-1.5 kW + 5 kWh battery + 3 kW inverter |
| Well pump (daily duty) | 1-3 kWh | Surge-rated inverter is the constraint; 0.8-1.2 kW array |
Which route wins, in one paragraph each
Close to the house: trench. One system, one inverter, utilities-grade reliability, and the marginal panel cost of covering the extra load is trivially small. This is also the only route that keeps a grid fallback without a generator.
Far, seasonal, or no-grid-at-all: the standalone kit. It swaps trenching cost for batteries and an inverter, it is movable if needs change, and for a distant well or gate it is often the only sensible answer. Treat the generator question honestly: a workshop that must run in a cloudy February wants either a bigger bank or a small backup.
Questions people ask
How do I power an outbuilding with solar?
Two routes. If the building sits within a practical trench of the house, extending circuits from a house array (or simply from the meter) is usually cheapest — one system, one inverter, one maintenance round. If the trench is long or the building is seasonal, a small standalone kit — a 1-2 kW array, a 5 kWh-class battery, and a 2-3 kW inverter sized to the biggest tool's surge — avoids trenching entirely and is the same technology as the off-grid build at hobby scale.
How much solar do I need for a shed or workshop?
Lights and phone charging take almost nothing — 200 W of panel and a small power station cover them. Real workshops size from the tools: a tablesaw or compressor drawing 1,500 W for an hour a day is 1.5 kWh; add lights and a charger and a busy weekend workshop lands near 3-5 kWh a day, which at 3.00/W means roughly a 1-1.5 kW array plus enough battery to start motors. Size the inverter to the surge load, not the daily total — that is the classic outbuilding mistake.
Is it cheaper to trench power from the house?
Usually yes, up to a distance where the trench stops being cheap. Trenching and conduit for a subpanel circuit typically runs from a few hundred dollars on a short, open run to a few thousand once distance, driveways, rock, or conduit-under-pavement enter it. Cross that line and a standalone kit wins — and if the outbuilding would be the property's only solar, compare both quotes against simply enlarging the house array instead.
Do the same rules as rooftop solar apply?
The electrical part does: wiring a separate structure has its own code requirements for grounding, disconnects, and burial depth, and a standalone system still needs an inverter rated for the environment (unheated sheds get cold; barns get dust). Incentive-wise, systems on outbuildings used for the residence historically qualified like rooftop ones — but the federal Residential Clean Energy Credit ended for systems completed after December 31, 2025, so treat any incentive as state or utility only and check your state page.
Sizing at performance ratio 0.8 and 3.00/W, the constants behind the calculator and the methodology page; load figures are typical planning values — last reviewed by SolarDime editorial. Electrical work on separate structures should be confirmed with a licensed installer against local code.
Data sources and assumptions
- Electricity ratesU.S. EIA · 2026 state averages
- Solar resourceNREL · 2026 state averages
- Federal tax treatmentIRS · Credit ended for installations completed after 31 Dec 2025 (P.L. 119-21)
- Installed costInstalled cost per watt · 2026 estimate, user-editable
State assumptions last reviewed: . Rules can change; verify your utility and state program before signing a contract. Full methodology.