Many times we are asked about snow on solar panels and how SunPump performs in parts of Canada and cold climates. We are happy to report that in most cases SunPump will produce heat even with a fresh snow covering. There are however limitations and conditions to that answer.
One of the common factors with homes in Edmonton, Kelowna, and Salmon Arm has been the equipment was “Right-Sized” using a good Heat Loss calculation method. Related to that, the larger buildings also have an auxiliary system is usually off, but is available during a cold-snap like we saw in BC for the entire month of December. It suggests that if SunPump can function without over-extending the heating burden by excessively long operating times, it fares well. In a few cases without any back up heat source, we have seen SunPump stressed and the performance degraded by an ice build up when over-used and without recovery. Sometimes all that was needed is the integrated 6 kW element to be wired, and the Mode setting switched from Eco (heat pump only), to Hybid (heat pump priority with 6 kW booster if needed).
Our observation is high snow climates should consider mounting the panels on a steep slope or even mounted under the roof overhang are the recommended adaptations. The majority of SunPump installs go along with the roof pitch and we support that routinely, as you will see in the pictures below. In one case the DIY owner placed the panels flat on a flat roof and it had ice accumulation during the cold-snap, partly because the back up was tripped and not contributing at all.
Let’s look at a few example homes that performed well during the 2016-17 cold snaps. The owner of the home shown at right was happy their SunPump was working well during the -10 to -20 C weeks in December 2016. The panels are those lumps covered by snow on the shed roof as an example of a low angle pitch. It is OK but shows the steeper roof helps shed snow. If the question is does the SunPump work covered in snow, the answer is yes it does. Could it be better at a steeper angle, we believe it would, but can adjust our expectations that this is a retrofit install that works in this condition.
SunPump has an unfair defrost advantage that does not require electric coil, compressor, or other outdoor heating that Air Source Heat Pumps need. The Sun is the natural defrost that can penetrate a moderate amount of snow and heat the black panel on a sub-zero afternoon.
Will solar black-body energy always work? No, of course not, but it often does and saves energy by not heating the outdoors. Part of that reason is the SunPump compressor and appliance is indoors so the majority of watts consumed to run the DC Inverter variable speed compressor becomes indoor heat gain – not heat loss like the Air Source Heat Pump split-type. When conditions are too much for SunPump there is also a choice of Manual or Automatic defrost modes with settings. When needed, a reversing valve can redirect heat from the storage tank to the panels to gently melt the snow. We like to see defrost minimized but understand that Right-Sizing is about the best compromise of meeting the largest number of annual heating hours while limiting over capacity inefficiencies. Sizing a system for the worst peak consumption hours of the year is more expensive than filling the peak demand with a backup system. Right-sizing is finding the best fit between economy and capacity.