Most solar conversations start at the wrong end. They begin with panels and batteries and end with a bill from an installer that the homeowner has no framework to evaluate. The right place to start is the question the panels are trying to answer: how much energy does the home actually use, and why. In a tropical climate, the honest answer to that question almost always points to insulation before it points to wattage.
This article is about sizing solar for a Panama home in a logical order. It uses the FRESH® brochure's own published energy data as worked examples and walks through what those numbers mean per day, where the AC load comes from, and how a sealed envelope changes the size of the system you need. It also explains, honestly, where the back-of-envelope arithmetic ends and where you need a solar engineer to take over.
Why insulation comes first
In a tropical climate, the largest energy load in most homes is air conditioning. Cooking, lighting, refrigeration, and electronics matter, but they sit on top of an HVAC bill that can easily be three to four times the size of all of them combined. The cheapest kilowatt-hour is the one you do not need to generate. The most efficient solar system is the one sized for a home that does not have to fight its own envelope.
FRESH walls and roof use Friopanel HP-PUR F insulated panels with a measured U-value of 0.11 W/m squared K and a thermal resistance (RT) of 21.36 m squared K per W. The brochure documents that this is roughly 20 to 40 times the thermal resistance of standard 15 cm hollow-block construction common in Panama. The practical consequence: HVAC energy use can drop by up to 70% compared to a concrete-walled home of the same size in the same climate. That is not a marketing number. It is the spec sheet, and it is the single most important number in any solar sizing conversation.
Our companion article on tropical insulation and AC bills covers the physics. For the purposes of solar sizing, what matters is that the system you specify for a Friopanel home is far smaller than the one you would specify for a hollow-block home of the same plan.
What the FRESH brochure data actually says
The brochure publishes a comparative HVAC energy table for two Panama climates. Both rows are for a 120 m squared home running the same comfort target, with the difference being the envelope.
Boca Chica (Pacific coast, near Chiriqui, hot and humid): a hollow-block home consumes roughly 21,600 kWh per year of HVAC energy. The same home built with Friopanel walls and roof consumes between 8,640 and 10,800 kWh per year. The annual saving sits in the range of $1,620 to $1,944 at typical local electricity rates.
Boquete (Chiriqui highlands, cooler and more temperate): a hollow-block home consumes around 9,600 kWh per year of HVAC. The same home with Friopanel uses roughly 3,840 to 4,800 kWh per year. Annual savings sit around $720 to $864.
Divide each of those numbers by 365 and you have a rough daily HVAC load to anchor your sizing thinking.
Daily HVAC load - approximate
At 120 m squared on the Pacific coast (Boca Chica), Friopanel HVAC works out to roughly 24 to 30 kWh per day. The hollow-block equivalent would be closer to 59 kWh per day. At 120 m squared in Boquete, Friopanel HVAC is roughly 10 to 13 kWh per day, versus around 26 kWh per day for hollow block.
These are HVAC kWh only. They do not include lights, fridges, ovens, electronics, pool pumps, water heaters, or anything else. Add those on top.
Building a household load estimate
For a total household load, HVAC from above is one input and the rest is conventional. Most tropical homes for a couple run somewhere in the range of 12 to 25 kWh per day for everything other than HVAC: refrigeration, lights, kitchen appliances, washer and dryer if electric, electronics, well pump and water heater if electric.
Combine that with the HVAC daily figures and the starting envelopes look like this:
- Pacific Friopanel home, 120 m squared: roughly 36 to 55 kWh per day total.
- Boquete-type highland Friopanel home, 120 m squared: roughly 22 to 38 kWh per day total.
- Pacific hollow-block equivalent, same plan: roughly 71 to 84 kWh per day total.
The gap is so large that the solar system size, and cost, follows it directly. Many off-grid systems become viable only once the envelope is doing its job.
How that maps to the FRESH standard models
The three FRESH standard models do not all sit at 120 m squared, so the brochure's table is a reference point rather than a direct match. Scale the numbers proportionally to footprint and adjust expectations.
The Cabana is roughly 30 m squared enclosed, with a total of around 43 m squared including the terrace. Its conditioned footprint is a quarter of the brochure's 120 m squared example. The Friopanel daily HVAC load for a Cabana on the Pacific coast is therefore in the order of 6 to 8 kWh per day; in Boquete-type climate, around 2.5 to 3.5 kWh per day. Add a typical solo or couple non-HVAC load of perhaps 10 to 14 kWh per day and the total daily envelope is roughly 16 to 22 kWh per day on the coast, 13 to 18 in the highlands.
The Casa (Bungalow Coco) sits closer to the brochure's example footprint when you include all conditioned space. Its energy profile tracks the 120 m squared example reasonably closely.
The Villa Sky, the largest standard model with extended terrace, scales modestly above the Casa. The Coco Beach villas in Puerto Armuelles, also built by Gatun Lake Construction, are at roughly 210 m squared each and were delivered solar-ready with water-treatment infrastructure. They are the worked example of a larger FRESH home pre-wired for a solar system.
From daily load to system size: the framework
This is where back-of-envelope arithmetic ends and engineering begins. The framework below is for orientation, not for specification.
Sizing the PV array
The rough rule of thumb is that one kilowatt of PV produces somewhere in the range of 4 to 5 kWh per day in Panama's solar resource, averaged across the year. Wet-season days produce less, dry-season days produce more. For a 25 kWh per day load, you are roughly looking at an array in the order of 5 to 7 kW of PV to cover the daily energy with margin for cloudy days. For a 50 kWh per day load, somewhere in the order of 10 to 14 kW. These are starting points only; the real number depends on orientation, shading, panel angle, and panel efficiency.
Sizing the battery
If the goal is to ride through nights and the occasional rainy day, the battery typically needs to cover one to two days of household load with safety margin. The real sizing depends on what you want to keep running at night (a fridge and lights only versus the full AC), discharge depth limits, and chemistry. Lithium systems are now the norm for new installs in Panama.
Grid-tie versus full off-grid
A grid-tied system uses the grid as the battery, exporting surplus during the day and drawing at night. It is generally the lowest-cost path if the lot has reliable utility power. A full off-grid system needs more PV and more battery, and is appropriate for remote sites without utility connection. Many FRESH lots, especially in Bocas del Toro or remote stretches of the Caribbean coast, sit in the off-grid category. Our off-grid home guide goes deeper on that path.
How FRESH solves this
The FRESH spec does the work that solar sizing depends on, before any solar conversation begins. The Friopanel envelope cuts HVAC energy by up to 70% relative to hollow block, which is the single biggest determinant of system size. The FRESH system page details the engineering.
Solar panels and off-grid water treatment are available as optional upgrades quoted per request. They are not part of the standard scope, because system size and cost depend entirely on lot, climate, and household load. What FRESH commits to is the envelope that lets a smaller system carry the home, and a build process that integrates the solar conduit, inverter location, and battery housing into the design before the home is assembled rather than adding them afterwards.
The Coco Beach villas in Puerto Armuelles are the documented example: solar-ready bungalows of roughly 210 m squared each, with the electrical and water-treatment infrastructure designed for off-grid or hybrid operation from the start. Gatun Lake Construction delivered those homes with the framework in place even where the specific PV and battery sizing was set per owner.
The honest disclaimer: actual PV and battery sizing is an engineering exercise. The numbers in this article are anchors for the conversation, not a quote. A solar engineer will model your specific lot's solar resource, your specific appliance list, your AC usage habits, and your grid-tie versus off-grid preference. Bring the FRESH envelope data into that conversation and the engineer can size accurately. Skip it, and the engineer will default to assumptions made for uninsulated buildings.
Frequently asked questions
Are solar panels included in the standard FRESH price?
No. Solar panels and off-grid water treatment are optional upgrades quoted per request, because system size and cost depend on the lot, the climate, the household load profile, and the choice between grid-tied and off-grid. The standard FRESH price covers the envelope, the foundation, and the utility infrastructure that lets solar integrate cleanly.
Why does insulation matter so much for solar sizing?
Air conditioning is the largest single load in most tropical homes. The Friopanel envelope cuts HVAC energy by up to 70% relative to hollow-block construction. A solar system sized for a Friopanel home is dramatically smaller, and cheaper, than one sized for the same plan in hollow block.
What is the difference between grid-tied and off-grid?
Grid-tied systems use the utility grid as the battery: surplus solar exports during the day, the grid covers the home at night. They are simpler and cheaper. Off-grid systems need a larger PV array and a battery bank to ride through nights and cloudy days. They are appropriate for remote lots without utility access. Hybrid systems combine both.
Can I add solar later, after the home is built?
Yes, but it is much easier and cheaper to integrate the conduit, inverter location, and any battery housing into the original design. Buyers who plan to go solar later still benefit from specifying a solar-ready configuration during the FRESH design stage.
Build with certainty
The right place to start a solar conversation is the envelope, not the panel count. The FRESH Friopanel system is the published data your solar engineer needs to size a smaller, smarter system. Walk through our standard models or get a fixed quote with the solar-ready option flagged at build your quote.