The right off-grid solar system depends on three separate requirements: the energy your cottage uses each day, the power appliances need at the same time, and the battery reserve you want when solar production is low. Start with those requirements before choosing a kit by its headline wattage.
A weekend property running a refrigerator and lights needs a different design from a year-round cottage with electric heating, a well pump and workshop equipment. Floor area alone cannot select the system.
1. Write down daily energy use
For each appliance, record watts and hours of operation. Multiply watts by hours to estimate watt-hours (Wh). Add the results and divide by 1,000 for kilowatt-hours (kWh). For cycling equipment such as a refrigerator, use a measured daily reading or a suitable energy-use estimate instead of treating its nameplate wattage as continuous consumption.
This illustrative load list is a calculation example, not a measurement of a typical Canadian cottage:
| Load | Assumption | Daily energy |
|---|---|---|
| Refrigerator | Assumed daily energy | 900 Wh |
| Eight LED lights | 8 × 8W × 4 hours | 256 Wh |
| Router | 12W × 8 hours | 96 Wh |
| Laptop | 60W × 3 hours | 180 Wh |
| Water pump | 500W × 0.25 hours | 125 Wh |
| Total | Before system losses | 1,557 Wh, or 1.557 kWh |
Add every load you actually intend to use. A kettle, microwave, water heater or electric space heater can change the design substantially. Keep essential loads separate from optional loads so you can decide what stays powered during poor weather.
2. Check simultaneous power and startup demand
Daily energy does not tell you the inverter size. A 1,500W appliance used for ten minutes consumes 250Wh, yet it still needs approximately 1,500W while running. Motors and compressors can also need a short startup surge.
List the appliances likely to operate together. Confirm continuous output, surge capability and whether your loads require 120V only or 120/240V split-phase. Then check that the selected battery can supply the required DC power. An inverter’s rating does not guarantee that every battery option can sustain that AC output on its own.
3. Choose battery reserve separately
Decide how many days of essential consumption you want to cover without useful solar input. For the illustrative 1.557kWh load list, two days require 3.114kWh delivered to those loads before allowing for inverter losses, battery discharge limits and other system consumption.
Use the selected battery’s usable-energy specification and the inverter’s operating characteristics. Nominal storage is not the same as energy delivered to AC appliances. Reserve for aging, temperature and future loads also needs a deliberate decision.
4. Design for the months you use the property
Check local, seasonal solar resource rather than using one Canada-wide sunlight assumption. Natural Resources Canada provides monthly solar-resource information, but its monthly values are indicative and do not fully capture snow, shading or every real-world loss. Annual grid-connected production estimates do not establish off-grid winter reliability.
Tell your designer whether you close the cottage for winter, visit occasionally, or live there year-round. Include shading, panel orientation, battery location and any compatible generator. A larger battery helps with reserve, but it also needs enough charging energy to recover after cloudy weather.
5. Compare kit specifications on the same basis
| Kit | Inverter rating | Solar array | Nominal battery choices |
|---|---|---|---|
| Growatt 3.5kW solar and battery kit | 3.5kW, 120V | 2.7kW | Growatt 5.12kWh or GSL 5kWh class |
| Growatt 6kW solar and battery kit | 6kW, 120/240V split-phase | 4.5kW | Growatt 10.24kWh or GSL 14.34kWh |
These are equipment comparisons, not recommendations for the example load list. Confirm battery discharge limits, the exact components included and optional racking before ordering.
Prepare a useful sizing request
Send your postal code, appliance list, daily energy estimate, simultaneous loads, any 240V equipment, seasons of occupancy, desired reserve and existing equipment. Include whether you need supply only or help finding an installation solution.
Use the cottage system finder to compare your daily energy, running loads, voltage and battery reserve with current kit options. Review the results and send the prepared sizing enquiry, or browse cottage solar kits.
Common questions
Can I choose a system by cottage square footage?
Use floor area as background only. Appliances, occupancy and energy habits determine the electrical requirements.
Does a 6kW kit contain 6kW of solar panels?
Not necessarily. In the kit above, 6kW describes inverter output and the array is 4.5kW. Always compare inverter kW, panel kW and battery kWh separately.
1 Comment
Yes want to know more, we are in Napierville, Quebec, canada, thank you