Do solar panels work in winter in Ottawa?

NRCan's photovoltaic potential database gives Ottawa these figures for panels facing south at latitude tilt, about 45° here, in kWh per kW of panels (read 2026-10-10). They already allow for system losses through a performance ratio of 0.75. NRCan calls its monthly values indicative: they leave out the effects of temperature and snowfall, which the sections below put back.

The same way they work in July. A solar panel turns light into electricity, and nothing about winter stops that. What changes is how much light reaches it. ECCC places the Ottawa airport station at 45°19′ N, so the noon sun stands about 21° above the horizon at the December solstice and about 68° in June (our arithmetic from that latitude and Earth's 23.4° tilt). A low sun spreads the same light over more surface, and the days are short.

Tilt decides how much of that light a panel catches. NRCan's figures for a flat array in Ottawa are 27 kWh per kW in December and 137 in July: winter falls to a fifth. At latitude tilt the same two months are 62 and 125, so winter holds at about half. NRCan's PV Ready Guidelines point low-slope and flat roofs to angled mounting kits, and they note that arrays at 15° or less shed snow poorly and do not perform as well in winter months.

A little. A panel's rated power is measured at a cell temperature of 25 °C, and a colder cell makes more power from the same light. Sandia National Laboratories' PV modelling guide sets out the PVWatts model's version of this: output scales with a temperature coefficient against that 25 °C reference. The pvlib modelling library gives typical coefficients of -0.2% to -0.5% per °C, so a cell running 20 °C below its rating makes roughly 4% to 10% more from the same light. The datasheet for a given panel states its own figure.

Ottawa supplies the cold. ECCC's normals put the airport's average daily high at -5.5 °C in January and -1.9 °C in December. A panel in sunshine runs warmer than the air around it, so the gain is real but modest, and it does nothing about the short days. Because NRCan's monthly figures leave temperature out, cold weather nudges real winter output above the table, and snow pulls it below.

Ottawa airport averages 231.9 cm of snowfall a year, 157.3 cm of it from December to February, with at least 1 cm on the ground on about 118 days and at least 10 cm on about 84 (ECCC, 1991 to 2020 normals). Snow that lands on a panel slides or melts off, and how quickly depends mostly on the tilt and on whether the snow has somewhere to go.

The longest Ontario record we found comes from the Sustainable Technologies Evaluation Program (STEP) of the Toronto and Region Conservation Authority. Its test lab near Toronto logged south-facing panels on poles at seven tilts, on a 30° roof section and on a ballasted flat deck from 2011 to 2017 (Janssen et al., Alternative Energy and Distributed Generation Journal, vol. 2 no. 2). Its estimated snow losses, as a share of each year's output and averaged over the seven years (our arithmetic on the study's Table 2):

The authors found that losses rose and fell with the year's total of daily snow depths, and that the steeper the panel, the smaller the loss. Ottawa airport averages 25 cm on the ground in January and 30 cm in February, so read the STEP figures as the pattern for an Ottawa array, not a forecast for your roof. The authors trace the extra loss on the roof section and the flat deck to snow collecting at the panels' bottom edge, on a flat ledge in the deck's case, so a steep panel with a clear low edge sits at the small end.

Federal research says the same about predicting snow losses. CanmetENERGY, NRCan's lab, compared the two snow loss models the solar industry uses against camera images and output from an array in Quebec, and concluded that the models still need work at other latitudes before anyone can predict snow losses accurately (Baldus-Jeursen et al., IEEE Journal of Photovoltaics, July 2023).

Usually not. The STEP figures put the cost of leaving snow alone at a few percent of a year's output, lost in the months that make the least power anyway.

Staying off the roof matters more. Writing about workplaces, Ontario's Ministry of Labour warns that anyone on a roof needs fall protection, that people below can be hurt by snow dumped from it, and that a cubic foot of snow weighs from 7 pounds when new and dry to 30 pounds when old and compacted (about 110 to 480 kg per cubic metre, our conversion).

Snow sliding off panels on its own needs the same respect. NRCan's PV Ready Guidelines call large sections of accumulated snow sliding off an array a hazard and describe snow clips and fences that slow and break up the release. The City of Ottawa asks that steps be taken to reduce uncontrolled sliding of snow and ice from panels close to roof edges. Keep doors, walkways and parked cars out from under the low edge of a roof array.

A ground mount changes the job: the panels stand within reach from the ground, and the racking can be set steep enough to shed snow by itself. If ice or a storm damages an array, we service and repair systems that other contractors installed as well as our own. Call (613) 869-8254.

NRCan's Ottawa table compares fixed angles facing south. A steeper array gives up some summer output, gains winter output and sheds snow sooner.

On a roof the pitch mostly sets the angle, and NRCan's guidelines recommend pitches of 4/12 to 18/12, 15° to 56°, for solar. On ground-mount solar panels the angle is a design choice: fixed, re-angled with the seasons, or on a tracker. In the STEP study, panels on poles shed snow better than roof modules at the same 30°, which is the winter case for a ground mount where the yard allows one.

For most homes the roof is still where to start. NRCan's guidelines call roof-mounted equipment the most cost-effective way to install solar in most residential applications, and our page on home solar panels in Ottawa covers roof age, direction and permits.

Net metering is why a weak December matters little on the bill. Your local distribution company (LDC) credits each exported kWh at the rates you pay and carries the dollar balance from bill to bill. Under section 8(8) of O. Reg. 541/05, the balance is written down to $0 only after credits have been carried forward in every billing period of the previous 12 months (e-Laws, read 2026-10-10).

Ottawa's seasons run that cycle for you. NRCan puts 722 of a year's 1,200 kWh per kW in March to August and 479 in September to February, so an array sized to a year of your use builds credit through spring and summer and spends it through the dark months. A winter bill that uses up the balance restarts the 12-month count, and nothing is written off. A balance still standing at the end of a winter is the sign of an array sized past your use.

The price plan shifts with the season too. On Time-of-Use, weekday hours from 11 a.m. to 5 p.m. are on-peak at 20.3¢ per kWh from May 1 to October 31 and mid-peak at 15.7¢ from November 1 to April 30, so a kWh exported at noon in January earns less credit than one in July. Ultra-Low Overnight keeps the same hours all year. On Tiered, the residential first tier grows from 600 kWh a month in summer to 1,000 in winter. These are the Ontario Energy Board's prices set for 2025-11-01, and the OEB sets new ones every November 1. The full rules, and the rebate a net-metered system gives up, are in our guide to net metering in Ontario.

Winter is a small part of that answer. NRCan rates Ottawa at 1,200 kWh per kW a year at latitude tilt, ahead of Toronto (1,163), Halifax (1,073) and Vancouver (1,007), and behind the Prairie cities we checked: Regina 1,360, Calgary 1,291, Winnipeg 1,272 and Edmonton 1,244. November to January supplies about a sixth of Ottawa's year, so the year's total, the price you pay and how your exports are credited decide whether it pays.

For Ontario in 2026, the published prices, the Home Renovation Savings rebate and the payback comparison are under Are solar panels worth it in Ontario? in our solar panel cost guide.