Solar for tiny homes: how to power 200 square feet off the grid

A tiny house is the awkward middle child of off-grid solar. It is too small to justify a ground-mounted array on most lots, and too big to run off the 100 W RV kit that worked on weekend trips. The roof realistically fits about 600 W of panels, which is enough for lights, devices, and a small fridge, but well short of what most tiny-home Instagram posts imply. This guide covers the three sizing tiers that actually map to tiny-house loads (300 / 600 / 1,200 W), the 12 V vs 24 V vs 48 V decision tree, the winter derate that shows up in Montana but not in Texas, and the cold-weather LiFePO4 charging rule that quietly bricks batteries. For broader context, see the off-grid solar kit guide and our breakdown of solar for off-grid living. For shed-scale builds first, solar power for a shed is the easier place to learn.

What a tiny house actually draws

Most tiny-house solar guides start with the panel. They should start with the load. A long-term tiny-house owner running off-grid in North Carolina logs around 3 kWh/day for his household versus roughly 30 kWh/day for a typical American home. Alfred University’s engineering-program tiny house, with no electric heat, models out to about 5.8 kWh/day annually — close to a real-world cap once you include a small fridge, lights, devices, and a water pump. Add electric heating and the number climbs by a factor of 5 or more.

Three realistic system tiers

Those daily-load numbers sort almost every tiny house into 3 tiers. They map cleanly to roof real estate, battery cost, and what you can run without rationing. Pick the tier from the load list above and the rest of the build follows.

12 V vs 24 V vs 48 V — the wire decides

The right system voltage is a function of how much current the wiring has to carry. Power equals volts times amps — at the same wattage, doubling the voltage halves the current and lets you halve the copper. For a 200 ft run between a ground-mounted array and a tiny house, that is the difference between #6 AWG and #10 AWG cable.

Lithium vs lead-acid in a cold climate

That voltage choice meets its first hard constraint at the battery. LiFePO4 is now the default for tiny-house solar — lighter, longer-lasting, and useable to 80% depth of discharge versus 50% for lead-acid — but it has one rule that lead-acid does not: you cannot charge it below freezing. Below 0 deg C (32 deg F), charging causes lithium plating: metallic lithium deposits on the anode, permanently reducing capacity and creating an internal short-circuit risk. A good BMS prevents charging when the cell is too cold, but the practical consequence is a tiny house in Montana that sees no battery charging on cold sunny mornings unless the battery box is heated.

The winter derate most articles skip

An LiFePO4 bank that is too cold to charge is one half of the winter problem. The other half is the panels. NREL’s PVWatts calculator, the standard tool the solar industry uses to model production, takes typical meteorological year (TMY) data from the National Solar Radiation Database and produces a month-by-month output estimate. Run the same array in Bozeman, Montana and Austin, Texas and the December numbers tell the story: winter peak sun hours in northern Montana drop to roughly 2.0 hours/day; central Texas stays above 4 hours. Designing off annual-average production gives you a system that works in October and fails in January.

Stationary vs trailer-mounted: the trade-off

That winter math gets more painful when the tiny house is on a trailer. Mobile tiny houses carry weight and aerodynamic penalties on every panel: a 300 W panel weighs 35 – 40 lb, and 4 of them on a metal roof shift the center of gravity. Stationary tiny houses have no such penalty — they can use heavier panels, deeper tilts, and a ground-mounted overflow array without compromise.

Costs and the honest payback math

A tiny-house solar system rarely pays back against a grid connection on its own. The case is stronger when you are paying for a utility hookup — sometimes USD 10,000 – 40,000 for a rural lot — that solar lets you skip entirely. A documented North Carolina build cost about USD 14,000 before federal tax credit, then an additional USD 5,000 for an expansion. After the 30% residential clean-energy credit, the net cost was closer to USD 13,000.

The takeaway

Tiny-house solar works inside narrower physical limits than most articles admit: about 600 W on the roof, 1,200 – 2,000 W if you can ground-mount, and a hard battery-charging floor at 0 deg C. Pick the tier from the loads you actually run, design the array off your worst-month sun hours, jump to 24 V the moment you cross 1,000 W of panel, and keep the battery bank above freezing. Do those four things and a tiny house off-grid in Montana is just as feasible as one in Austin — it just needs more panel and a heated battery box. For wiring this safely with permits, our shed guide covers the NEC side, and the off-grid living article scales the same playbook up to a small house.