Off-Grid Builds: a tiny house on solar
A 24V sample system for a tiny house with a full-size fridge, internet, lights and small appliances.
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For about 3,000 Wh a day, our sample uses six 12V 100Ah LiFePO4 batteries wired as a 24V bank (7,680 Wh), 1,000W of solar and a Victron 100/50 MPPT. At this size, 24V halves the current compared with 12V.
- About 3,000 Wh/day of example loads.
- 24V keeps cable sizes reasonable.
- Plan for winter sun or a backup generator.
The load list
Example loads; replace them with yours in the Power Planner.
| Device | Watts × hours | Wh/day |
|---|---|---|
| Full-size fridge (EnergyGuide 400 kWh/yr example) | ≈46 W average × 24 h | 1,096 |
| Internet | 15 W × 24 h | 360 |
| LED lights | 60 W × 5 h | 300 |
| Laptop, TV, phones | 150 W × 4 h | 600 |
| Water pump, small appliances (example) | varies | 644 |
| Total | 3,000 |
Sizing math
Battery: 3,000 Wh/day × 1.5 day(s) of autonomy ÷ 0.92 inverter ÷ 0.80 usable ≈ 6,114 Wh (0.92 from the NREL PVWatts manual, 0.80 from Victron LiFePO4 data). 6 × 12V 100Ah LiFePO4 batteries (1,280 Wh each: 12.8V × 100Ah) give 7,680 Wh as a 24V (2 in series × 3 in parallel) bank. See how to size a battery bank.
Confirm the battery maker allows series wiring and the series/parallel count you plan.
Solar: 3,000 Wh ÷ (4 peak sun hours × 0.77, the PVWatts V1 derate) ≈ 974 W of panels. We use 1000W. Check your site's sun hours in NREL PVWatts and size for your worst month. See solar panel sizing.
Controller: Victron rates the 100/50 for 1,400W nominal PV on a 24V battery, so 1,000W fits. Wire panels so the cold-weather open-circuit voltage stays below the controller's 100V limit.
Inverter: you'll need a 24V inverter (the Renogy P2 units in our picks are 12V models). Size it for the largest simultaneous AC load plus the fridge's start-up surge. See system voltage.
Parts list
The main parts. Size fuses, breakers and cable from each maker's manual and a wire-gauge table.
LiTime 12V 100Ah LiFePO4 battery (Group 24)
Six of these as a 2S3P 24V bank.
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Renogy 200W solar panel
Five 200W panels for a 1,000W array.
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Victron SmartSolar MPPT 100/50
Rated for 1,400W of PV on 24V.
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Victron SmartShunt 500A battery monitor
Tracks a 24V bank's state of charge.
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Klein Tools MM400 multimeter
Check series voltages before connecting.
Check price on Amazon (opens in a new tab)Wiring outline
Array → PV disconnect → MPPT → 24V fused bus → batteries (series pairs, then paralleled with equal cable lengths). 24V inverter on its own fuse and battery switch. A 24V-to-12V converter feeds any 12V loads.
This is a planning outline, not a wiring diagram. Follow each manufacturer's manual, fuse every positive conductor close to the battery, and have a qualified installer check the work. Local codes apply to buildings and vehicles.
FAQ
Why not 12V?
At 3,000 Wh/day with surge loads, 12V currents get high and need very thick cable.
Where do I go next?
Try the power planner to put numbers to your own situation, or see the product picks on the deals page.
Terms used here
- Watt (W)
- Rate of power use or production.
- Watt-hour (Wh)
- Energy: one watt for one hour.
- Kilowatt-hour (kWh)
- 1,000 watt-hours.
- State of charge (SoC)
- How full a battery is, as a percentage.
- LiFePO4 (LFP)
- Lithium iron phosphate battery chemistry.
- Inverter
- Converts DC battery power to AC household power.
- MPPT
- Maximum power point tracking controller.
- Peak sun hours
- Hours of equivalent 1,000 W/m² sunlight per day.
- Derate
- Factor for real-world losses in solar output.
- Open-circuit voltage (Voc)
- Panel voltage with no load; rises in cold.
Sources
This guide is informational and based on published specifications and general references, not hands-on testing. Check the manufacturer's current specs before you buy.