Two Cabins, One Solar System?

What to Know When Powering Buildings 450 Feet Apart Off-Grid

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  • Introduction
  • The Challenge: Running AC Power Over Long Distances
  • Wire Size Guide at 450 ft
  • One Central System for Both Cabins?
  • Two Separate Solar Systems?
  • Don’t Forget the Trench
  • Conclusion

Introduction

In last week’s article, I introduced a recent project involving a customer who owns a 20-acre property with two cabins about 450 feet apart. She reached out for help designing an off-grid solar system, initially to power one cabin, but with a long-term goal of supplying energy to both.

That raises a common question we get when working with larger, off-grid properties:

Should I install one large solar power system and run AC power between the cabins, or build two independent systems, one for each cabin?

If you’ve got multiple buildings on a large property, whether it’s cabins, workshops, or homes, this decision comes up often. And when those buildings are hundreds of feet apart, like in this case, it’s not always an obvious answer.

I want to explore the pros and cons of both options, look at the wire sizes needed for a 450-foot AC run, and help you decide what setup might make the most sense for your land.

The Challenge: Running AC Power Over Long Distances

When running AC power over long distances, voltage drop becomes a critical factor. As electricity travels through copper wire, a small amount of energy is lost as heat, which results in a drop in voltage. If too much voltage is lost, appliances at the far end may not operate properly, or worse, the system may become unsafe or unreliable. That’s why, in most residential or off-grid installations, we aim to keep the voltage drop within 3% of the source voltage. Staying within this limit helps ensure that devices run efficiently and that the system meets electrical code standards.

Example Scenario:

  • 450 ft one-way cable run (900 ft round-trip)
  • Single-phase AC or Split-phase AC
  • Copper wire
  • Target: ≤ 3% voltage drop
  • Voltage: 120V or 240V

Wire Size Guide at 450 ft

One Central System for Both Cabins?

Advantages:

  • One set of core components: inverter, battery bank, charge controller
  • Easier system monitoring and maintenance
  • Can centralize backup systems (like a generator)

Disadvantages:

  • Long AC wire run (450 ft) requires thick, expensive cable
  • Voltage drop risks, especially if the second cabin draws high current
  • Less redundancy: if the central system fails, both cabins lose power

Two Separate Solar Systems?

Advantages:

  • No long AC wire runs, systems stay close to loads
  • Each cabin operates independently
  • Easier to design system size to each cabin’s unique load

Disadvantages:

  • Duplicates cost for inverters, batteries, and controllers
  • More maintenance and monitoring effort
  • Potential inefficiency if one cabin’s system is rarely used but in this case they eventually will both be used on a daily basis.

Don’t Forget the Trench

If you decide to power both cabins from a single solar system, you'll need to run an AC power line 450 feet across your property, and this means digging a trench that meets electrical code.

Here’s what that typically involves:

Typical Trench Depths (Canada/US)

  • 24 inches (minimum) if the wire is in conduit (e.g., PVC or EMT)
  • 18 inches (minimum) for direct burial-rated cable with added protection (like a GFCI breaker)
  • Always check local code, some jurisdictions require deeper trenches, especially in areas with frost.

Proper Layering in the Trench

  1. Bottom layer: Smooth sand or clean fill (3–6 inches) to prevent sharp rocks from damaging the cable or conduit.
  2. Cable or conduit is laid in the trench.
  3. Top layer of sand (another 6 inches) covers the cable/conduit.
  4. A warning/danger tape (usually red or yellow) is placed 12 inches above the cable, this helps future diggers avoid accidental strikes.
  5. Backfill with soil on top.

Conclusion

In this particular project, the customer walked the property to assess the best route for running the cable. Following the existing road would have meant a longer trench, adding even more distance to the already 450-foot span. But going straight across the land, while shorter on paper, meant cutting through rocky, uneven terrain.

With the cost of large-gauge copper wire already high, the added labor and machinery needed to trench through tough ground would have significantly increased the installation cost.

The result?
She made the smart call to focus on two separate off-grid solar systems, one for each cabin. This avoided the trenching challenge altogether and gave her more flexibility in how each cabin could be powered, scaled, and maintained independently.

Although it turned out to be an easy decision in the end, it was still a great idea to explore the possibility of running one system for both cabins. Taking the time to walk the land, evaluate trenching routes, and crunch the numbers helped us understand all the variables involved, from wire sizing to terrain conditions to long-term cost.

At IOTG Solar, we believe it's our job to explore every realistic option, even if it doesn’t pan out. Without doing this due diligence, we might have missed a better system design entirely, and that wouldn’t be good enough for our customers or for us.

We help our clients design reliable, smart off-grid systems customized to how they really live. Whether it’s a centralized solution or two standalone systems, the key is planning for efficiency, durability, and future expansion.

If you're considering a setup like this and want help modeling your load and wire sizing, feel free to reach out. We’re always happy to help you get it right the first time.

IOTG SOLAR LTD 5 Critical Mistakes To Avoid Before Buying Solar.pdf

For individuals seeking consultation, education, or assistance in system designs related to grid-tie or off-grid solar applications, IOTG Solar stands ready to help. Our team is available to address questions, provide valuable insights, and offer support at every stage of the solar energy journey. Feel free to reach out to IOTG Solar anytime for expert assistance and comprehensive solutions tailored to your specific needs.

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