Free tool
Off-Grid Solar Calculator for Tiny Houses
Size a tiny house solar system from the ground up. List your appliances, choose your sun hours, backup days and battery type, and get your daily energy use, solar array size, number of panels, battery bank, inverter and a rough budget.
- Editable appliance list
- LiFePO4 or lead-acid batteries
- 12, 24 or 48 V systems
How to size tiny house solar
Off-grid solar sizing starts with one number: how many watt-hours you use per day. Everything else, from the number of panels to the size of the battery bank, follows from it. A frugal tiny house with LED lights, a 12 V fridge, laptops and a water pump might use 1 to 2 kWh a day. Add a mini-split, induction cooking or an electric water heater and that can jump to 5 to 15 kWh, which changes the system from a modest DIY project into a serious investment. This off-grid solar calculator from Tiny Homes Blueprint shows you where your energy goes, so you can decide what to power with the sun and what to run on propane or wood.
How the calculator works
- Daily energy: each appliance's watts × hours per day × quantity, added together.
- Solar array: daily energy ÷ peak sun hours ÷ 0.75, allowing about 25% for real-world losses from heat, wiring, charge controller and inverter efficiency, dust and panel angle. The result is rounded up to whole 400 W panels.
- Battery bank: daily energy × days of autonomy ÷ usable depth of discharge, shown in kWh and in amp-hours at your system voltage.
- Inverter: your peak load × 1.25, rounded up to a common inverter size. Peak load assumes all smaller loads can run together, plus your single largest heavy appliance.
| Assumption | Value used |
|---|---|
| System losses | ~25% (array sized at daily use ÷ sun hours ÷ 0.75) |
| Panel size | 400 W |
| LiFePO4 usable depth of discharge | 80% (rated 80–90%; we use the conservative end) |
| Lead-acid usable depth of discharge | 50% |
| Inverter headroom | Peak load × 1.25 |
| Charge controller | Array watts ÷ battery voltage × 1.25 |
| Equipment prices | Panels $0.50–0.90/W, LiFePO4 $250–450/kWh, lead-acid $150–300/kWh, inverter $0.35–0.75/W, plus $800–2,500 for controller, wiring and racking |
| Professional installation | About 1.6–2.2× equipment cost |
For a typical full-time tiny house, an installed off-grid system usually lands somewhere around $8,000 to $30,000, which is the range our tiny house cost calculator uses.
Typical daily use for off-grid tiny houses
| Household type | Daily use | What it usually runs |
|---|---|---|
| Weekend cabin | 0.5–1 kWh | Lights, phones, a fan and a water pump |
| Frugal full-time | 1–2.5 kWh | Adds a 12 V fridge, laptops, Wi-Fi and a TV |
| Comfortable full-time | 3–6 kWh | Adds a washer, microwave and some mini-split use |
| All-electric | 8–15+ kWh | Induction cooking, daily heating or cooling, electric hot water |
How to use your result
- Cut loads before adding panels. Every 1,000 Wh you remove from your daily use saves roughly 300–350 W of panels and 2.5 kWh or more of battery. Heavy heating loads are the first place to look.
- Size for your worst month. If you live there year-round, rerun the calculator with winter sun hours (often 2–3 in the northern US). Many off-grid homes add a small generator for long cloudy spells instead of oversizing the battery.
- Choose the voltage early. 12 V suits small systems under about 1,500 W of inverter. 24 V or 48 V keeps current and wire sizes manageable for anything larger.
- Plan the roof. A 400 W panel is roughly 3.7 x 5.6 ft. A tiny house roof may only fit 4 to 8 panels, so larger arrays often go on a ground mount. Check your design against our tiny house on wheels plans or small cabin plans.
Tips for an efficient off-grid tiny house
- Heat water and food with propane. A propane tankless water heater and cooktop remove the two biggest resistive loads from your solar budget.
- Insulate and air-seal well. A tight, well-insulated shell needs far less heating and cooling. 2x6 walls or SIPs help, though they add weight on a trailer; check with the trailer weight calculator.
- Buy efficient appliances. A DC compressor fridge, LED lighting and a laptop instead of a desktop can halve a typical daily load.
- Pick LiFePO4 if you can. Lithium iron phosphate batteries cost more up front but last several times as many cycles as lead-acid, need no maintenance and can be discharged deeper.
- Mind the water. A 12 V pump uses little power, but a deep well pump can be one of the biggest surge loads in the house.
Building on rural land? Read our guide to building a tiny house for how utilities fit into the build sequence, and see the A-frame and small farmhouse pages for off-grid-friendly designs.
Frequently Asked Questions
How many solar panels does a tiny house need?
Most off-grid tiny houses need about 4 to 10 400 W panels (1,600 to 4,000 W). A frugal home using about 1.5 kWh a day in a sunny region may get by with 2 or 3 panels, while one running a mini-split or induction cooktop may need 10 or more.
How much battery storage does an off-grid tiny house need?
Multiply your daily use by the number of cloudy days you want to ride through, then divide by the usable depth of discharge. For 2 kWh a day and 2 days of backup on LiFePO4, that is about 5 kWh of battery.
Can I run air conditioning on solar in a tiny house?
Yes, an efficient mini-split can run on solar, but cooling and heating are usually the largest loads in an off-grid house. Expect to need a bigger array, a larger battery and a 24 V or 48 V system.
Should I use a 12 V, 24 V or 48 V system?
12 V is simple and fine for small systems with inverters under about 1,500 W. For larger systems, 24 V or 48 V cut the current in half or by three-quarters, which means thinner cables, less heat and better efficiency.
How much does an off-grid solar system cost for a tiny house?
Equipment for a small system can start around $3,000 to $6,000 if you install it yourself. A professionally installed system sized for full-time living typically runs about $8,000 to $30,000 depending on loads and battery size.
Related tools and guides
Designing an off-grid tiny home?
Tiny Homes Blueprint plans can be adapted for solar, propane and composting systems. Ask us about your site.