Tiny Home Solar Needs Calculator

Why Solar Fits Tiny Living

Tiny homes emphasize simplicity, efficiency, and independence. With a smaller footprint than a conventional house, your energy needs are usually lower, which makes solar power an excellent match. A well sized off‑grid system can keep lights, a small fridge, fans, and electronics running without a generator or a full utility connection.

This tiny home solar needs calculator helps you estimate how many solar panels and how much battery storage are appropriate for your setup. By entering your daily energy use, the wattage of your panels, the average sun hours at your location, and an overall system efficiency factor, you get a quick sizing baseline before you talk to an installer or buy equipment.

How the Tiny Home Solar Calculation Works

The calculator uses a simplified version of standard off‑grid solar sizing practice. It focuses on daily energy balance rather than detailed engineering design.

Key Inputs

• Daily Energy Use (E) – your total electricity consumption per day, in kilowatt‑hours (kWh). Many tiny homes fall roughly in the 2–6 kWh/day range, but full‑electric setups with electric heat or cooking can be higher.
• Panel Wattage (P) – the rated power of one solar panel in watts (W), such as 200 W or 400 W.
• Sun Hours per Day (H) – also called peak sun hours. This is an average number of hours per day when sunlight intensity is equivalent to full sun.
• System Efficiency (η) – a percentage that accounts for losses in the system (inverter, wiring, battery charge/discharge, dirt on panels, etc.). Many tiny home systems fall between 70–85 %.
• Autonomy Days (D) – how many days you want your battery bank to power the home without solar input, for example during cloudy weather.

Formulas Used

First, the calculator finds how much energy one panel can contribute in a typical day. Because panel wattage is in watts and energy is in kilowatt‑hours, we divide by 1000 to convert watts to kilowatts.

Daily panel energy (kWh/day) = (P / 1000) × H × (η / 100)

Then, the number of panels needed to cover your daily usage is:

Panel count (N) = E ÷ [ (P / 1000) × H × (η / 100) ]

The calculator always rounds this up to the next whole number, because you cannot install a fraction of a panel.

Battery capacity is sized from your daily use and your desired autonomy days:

Battery capacity (kWh) = E × D

In MathML form, the panel count formula can be expressed as:

This simple model gives you a practical starting point for comparing different system sizes and configurations.

Interpreting Your Results

After you enter your values and click the calculate button, the tool shows two main outputs:

• Recommended number of solar panels – the minimum whole number of panels needed to meet your average daily use, given your assumptions.
• Estimated battery storage (kWh) – the amount of stored energy needed to ride through your chosen number of autonomy days.

Use these results as planning guidance rather than an exact build list. A few practical points when you read the output:

• If the panel count seems impossible to fit on your roof, you may need higher wattage panels, better site conditions (more sun hours), or to reduce your energy use.
• If the battery capacity looks very large, consider whether you truly need that many autonomy days or whether you can tolerate occasional generator use or conservation during storms.
• Always check both energy (kWh) and power (kW). This calculator works in kWh; you will still need to ensure your inverter and wiring are large enough for your peak loads.

Worked Example: Full‑Time Tiny Home

Imagine a full‑time tiny home on a trailer, occupied by one person working remotely. The home has an efficient 12 V fridge, LED lighting, a laptop, a small induction cooktop used lightly, and a mini‑split heat pump for shoulder seasons. After estimating or measuring every appliance, you arrive at about 4 kWh/day of electricity use.

Step 1: Choose Panel Wattage and Sun Hours

You decide on 400 W solar panels to make better use of the limited roof area. Your location averages around 5 peak sun hours per day over the year. You assume system efficiency of 75 % to cover typical losses.

Daily energy from a single panel is:

Panel energy = (400 / 1000) × 5 × (75 / 100)
             = 0.4 × 5 × 0.75
             = 1.5 kWh/day per panel (approx.)

Step 2: Compute Panel Count

N = E ÷ panel_energy
  = 4 ÷ 1.5
  ≈ 2.67 panels

Because you cannot install a fraction of a panel, the calculator rounds up to 3 panels. In practice, you may choose to go to 4 panels to add a margin for cloudy weather or future loads.

Step 3: Size the Battery Bank

You want at least 2 days of autonomy so that you can ride through short cloudy periods without a generator.

Battery capacity = E × D
                 = 4 kWh/day × 2 days
                 = 8 kWh

An 8 kWh battery bank could be provided by, for example, a lithium battery system rated for 48 V and around 170 Ah usable capacity (actual configurations vary by chemistry and brand). If you choose lead‑acid batteries, you would typically install a larger nameplate capacity to account for lower usable depth of discharge.

Typical Tiny Home Scenarios (Comparison Table)

The table below illustrates how different lifestyles and energy habits can change system size. These scenarios use the same basic formulas as the calculator. They assume 400 W panels, 5 sun hours, and 75 % efficiency, unless noted.

Use this table as a reality check. If your calculator output is far outside these ranges, double‑check your inputs for typos or unrealistic assumptions.

Gathering Accurate Inputs

Your results will only be as accurate as the numbers you enter. For daily energy use in particular, a careful estimate goes a long way.

Estimating Daily Energy Use

• List every appliance and device you plan to use: fridge, water pump, lights, fans, laptops, router, TV, tools, etc.
• Note each item’s watt rating (from the label or manual) and estimate how many hours per day it runs.
• Multiply watts × hours for each item to get watt‑hours per day, then divide by 1000 to convert to kWh.
• Add everything together to get your total daily kWh.

As a rough guide:

• Very simple weekend use (few lights, phone charging, small fridge) may be near 1–2 kWh/day.
• Comfortable full‑time living often runs 3–6 kWh/day.
• Electric cooking, resistance heating, or large entertainment systems can easily push you beyond 6–8 kWh/day.

Understanding Sun Hours and Efficiency

Sun hours are not the same as daylight hours. A location might have 12 hours of daylight but only 4–6 peak sun hours after accounting for lower angles and clouds. Solar resource maps and local solar installers can help you find typical peak sun hours for your area.

System efficiency rolls several real‑world losses into one number:

• Inverter efficiency (often 90–96 % for modern units)
• Wiring and connection losses
• Battery charge/discharge losses
• Dirt or snow on panels and non‑ideal mounting angles

For a portable or DIY system, 70–80 % is a reasonable planning range. A carefully designed fixed installation might justify a slightly higher efficiency assumption.

Battery Chemistry and Practical Choices

The calculator outputs battery capacity in kWh and does not assume a specific battery type. In practice, your choice of chemistry affects cost, weight, and usable capacity.

• Lithium iron phosphate (LiFePO₄) – Higher upfront cost but lighter and more compact. Commonly allows deeper discharge (for example, 80 % usable), which means you need less nameplate capacity for the same usable kWh.
• Lead‑acid (flooded, AGM, or gel) – Lower sticker price but heavier and bulkier. To preserve lifespan, you usually limit depth of discharge (for example, 50 % usable), so installed capacity must be larger than the usable number from the calculator.

Whatever you choose, match your battery system’s nominal voltage and capacity to inverter and charge controller specifications recommended by a qualified solar professional.

Calculator Assumptions and Limitations

This tool is designed as a planning aid for tiny home owners, not a full engineering design. It makes several simplifying assumptions:

• Average conditions only – Results are based on an average daily sun hours value and do not capture week‑to‑week weather swings.
• No detailed seasonal modeling – Winter and summer performance can differ significantly. The calculator does not vary sun hours or loads by season.
• Combined efficiency factor – All system losses are bundled into a single efficiency percentage, instead of modeling each component separately.
• Energy‑based sizing – The calculation focuses on daily energy (kWh). It does not check whether your inverter and wiring can safely handle peak power (kW) from multiple devices running at once.
• No shading or snow modeling – Tree shading, nearby buildings, snow cover, and dirt accumulation are not explicitly included.
• Standard panel orientation – It assumes panels are installed at a reasonably suitable tilt and azimuth. Roof‑mounted panels on a tiny home may face compromises based on roof shape.
• Planning‑level accuracy – Outputs are intended as starting estimates to support conversations with installers or further design work, not as stamped construction documents.

Next Steps After Using the Calculator

Once you have a sense of your panel count and battery size, consider:

• Comparing different panel wattages to see how roof space constraints affect your design.
• Experimenting with lower or higher autonomy days to balance reliability, cost, and storage space.
• Refining your energy audit as your appliance list becomes more concrete.
• Discussing your assumptions with a qualified solar designer or electrician before purchasing equipment.

This structured approach helps ensure your tiny home solar system is sized realistically for your lifestyle, budget, and location, while acknowledging the inherent uncertainties of weather and real‑world usage.