An off-grid solar system for a winter cottage has two jobs: make enough power on short, cloudy December days, and keep its lithium batteries above freezing so they can charge. This guide walks through sizing a system for winter use, from estimating your daily energy to choosing panels, battery and inverter, and explains the ways to keep LiFePO4 batteries warm in a cottage that isn't heated all the time.
Why winter changes the sizing
A cottage that only runs from May to October can get by with a fairly small array. Winter is harder for three reasons:
- Less sun: days are shorter and the sun is lower, so the same panels make much less energy in December than in June.
- Snow: panels covered in snow produce little until it slides off or is cleared.
- Cold batteries: LiFePO4 batteries should not be charged below 0°C unless they have built-in heating. A battery sitting in an unheated cottage at −15°C can't take a charge, even on a sunny day.
So a winter system is sized around your worst month, not your average one, and the battery location is planned before you buy anything.
Step 1: Estimate your daily energy use
List what will run in winter and how many hours a day. Your appliance labels or manuals give the watts; multiply by hours to get watt-hours (Wh). Heating is the big decision: electric baseboard heat is not practical on a typical off-grid cottage system, so most winter cottages heat with wood, propane or oil and use solar for the fan, pump, lights and appliances.
Here is an example for a cottage used on winter weekends, heated with a propane furnace. Your numbers will differ, so replace each line with your own:
| Load | Example use per day |
|---|---|
| Refrigerator | About 1.5 kWh |
| Propane furnace blower fan | About 1.5 kWh |
| Well or pressure pump | About 0.5 kWh |
| LED lighting | About 0.5 kWh |
| Internet, phones, laptop, TV | About 0.5 kWh |
| Kitchen and small tools (kettle, microwave, coffee maker) | About 0.5 kWh |
| Total | About 5 kWh per day |
Add the inverter's own standby use from its manual, since an off-grid inverter that stays on all week uses some energy even with nothing running.
Step 2: Size the battery for cloudy days
In winter there can be several grey days in a row, so plan battery storage for at least two days of use without sun. At 5 kWh a day, that is about 10 kWh of usable storage.
One GSL 14.34 kWh wall-mount battery stores 14.34 kWh nominal, with 13.6 kWh available at the 95% depth of discharge listed on our kit pages. That covers the example with some margin for conversion losses. If you will run a well pump, a bigger fridge or power tools, or stay full-time, plan for two batteries.
Power matters too. Each GSL battery is rated 100A recommended and 150A maximum at 51.2V, so one battery supplies roughly 5 kW continuously. Large loads that start together (a well pump and microwave, for example) may need a second battery even if the energy total looks small.
Step 3: Size the solar array for December
Natural Resources Canada publishes photovoltaic potential maps for Canada (page last modified January 16, 2025), with monthly values for more than 3,500 municipalities and several panel tilts. Look up your cottage's municipality and note the December value in kWh per kW of panels.
Then the maths is simple:
Panels needed (kW) = daily use (kWh) ÷ December output per kW per day (kWh) × 1.2
The 1.2 adds a margin for wiring, inverter and battery losses. As an example, if the map showed 45 kWh/kW for December at your site, that is about 1.5 kWh per kW per day. For 5 kWh a day: 5 ÷ 1.5 × 1.2 = 4 kW of panels. Sites with more winter sun need less; shaded lots and sites with less winter sun need more.
Snow is the other factor. NRCan's maps also compare panels tilted at your latitude, at latitude +15° and vertical. Steeper angles collect more of the low winter sun and generally help snow slide off. If you mount panels on the ground, leave enough clearance below them for snow to pile up without covering the bottom row.
Step 4: Choose an inverter and kit
Match the inverter to your largest loads and your wiring: 120V for a small cabin, or 120/240V split-phase if you have a well pump or other 240V equipment. These Growatt off-grid kits are sold through our off-grid solar systems for homes and cottages collection:
| Kit | Inverter output | Panels | Battery | Price (as of October 2026) |
|---|---|---|---|---|
| Growatt 3.5kW off-grid kit | 3,500W, 120V | 6 × 450W (2.7 kW) | Growatt ALP 5.12 kWh or GSL 5 kWh | C$5,599.99 (GSL) / C$6,599.99 (ALP) |
| Growatt 6kW off-grid kit | 6,000W, 120/240V split-phase | 10 × 450W (4.5 kW) | 1 × GSL 14.34 kWh | C$7,699.99 |
| Growatt 12kW off-grid kit | 12,000W, 120/240V split-phase | 20 × 450W (9 kW) | 1 or 2 × GSL 14.34 kWh | C$10,799.99 / C$14,899.99 |
For the 5 kWh-a-day example, the 6kW kit lines up well: 4.5 kW of panels and 14.34 kWh of storage. The 3.5kW kit suits a smaller, 120V cabin used mostly in spring, summer and fall, and the 12kW kit suits a larger cottage or full-time winter use. Racking, freight and installation are extra. Prices change, so check each product page for the current price.
All three inverters can take a compatible generator as a second power source, according to their product pages. For a winter cottage, a generator is a sensible backup for long cloudy stretches.
Keeping batteries warm
The GSL 14.34 kWh battery charges between 0°C and 45°C in its standard version. It is an IP20 indoor battery, built for dry indoor locations. You have three main options:
| Option | Works best when | Things to plan for |
|---|---|---|
| Install in a heated space | The cottage is heated all winter, or a utility room is kept above freezing | Heat source must stay on while you're away |
| Self-heating GSL battery | The cottage is left unheated between visits | C$4,279.99 vs C$4,139.99 for the standard model (as of October 2026); may be built to order, so call for lead time |
| Dedicated enclosure or room | You want the battery out of the living space | Must follow the battery and inverter manuals and your electrical code for ventilation, clearances and protection |
The self-heating version warms its cells before charging when they are below 0°C, so solar can recharge it in an unheated building. The inverters in these kits should also be installed in a dry, ventilated, protected location, so check each manual's operating temperature range before putting equipment in an unheated space.
Winter checklist
- Use the included Wi-Fi monitoring module, if the cottage has internet, to check battery charge while you're away.
- Turn off loads you don't need between visits so the battery isn't drained during a cloudy week.
- Clear snow from panels only when it is safe to do so from the ground; never climb onto a snowy roof.
- Have a licensed electrician do the installation, with any permit and inspection your province requires (in Ontario, through the Electrical Safety Authority).
Frequently asked questions
Can solar panels handle Canadian snow and cold?
The Canadian Solar 450W panels in these kits are rated for snow loads up to 8,100 Pa and an operating range of −40°C to +85°C, under the manufacturer's mounting conditions. Those ratings apply to the panels, not the inverter or battery.
Can I leave the system on while the cottage is empty?
Yes, if it is sized for the loads you leave on, such as a fridge, pump or heat-trace cable. Size the battery and panels for those loads, use a self-heating battery or a heated space, and keep a generator option for long cloudy spells.
Do I need a self-heating battery if I heat with wood?
If the battery's room drops below 0°C between visits, yes. A wood stove only keeps the battery warm while it's burning.
Can I add more batteries later?
Yes. GSL 14.34 kWh batteries connect in parallel, and the 12kW kit is sold with one or two. Additional batteries need correctly sized connections, protection and communication settings, as set out in the equipment manuals.
Not sure what size you need? Send us your winter loads or call 1-800-858-4318. Our team in Waterloo, Ontario will help you size an off-grid kit for your cottage.