A friend contacted me for advice on electric heat in her home. She is considering installing a Convectair Allegro. I thought this might perhaps be of value to others.
Electric Heat
There are 2 key measures to consider. Efficiency & Efficacy
Efficiency (unit in %) = (power_output – losses) / power_output
For example, a gas furnace suffers (combustion loss) + (blower-loss) + (stack-loss)
In theory, all electric radiant heating is 100% efficient, as there are 0 losses. However, in practice, electric radiant heat is mounted low down on an outside wall beneath windows. Some energy (small%) is radiated to the back of the unit, which is convected through the wall to the outside. In addition the heated air convects directly upwards where it becomes trapped between drawn curtains & the cold windows.
Minimizing losses begins with understanding the causes. However, the important point is that even the cheapest electric radiant heater (baseboard) converts 100% of the energy directly into heat, with 0 loss. 100% is as good as it gets, regardless of what any salesman says.
While the Convectair sales-pitch claim is for superior efficiency, it is just a sales-pitch. Two things differentiate the Convectair heater from electric radiant baseboard.
1) Concentrates up to 2000W into a relatively small wall-space, whereas electric baseboard heaters roughly produce 250W per foot of linear length. The sales-pitch for the Allegro-Duo claims “provides gentle, palpable heat”. True I guess, but all heat is.
2) Has a fairly sophisticated automatic control thermostat. This can save you some money, but it does not change it’s efficiency. 100% efficient is still maximum… exactly the same as any electric radiant heater. How much money the smart thermostat can save depends on the person. If you tend to forget & leave heat turned up when you are not at home, then plenty $savings. The automatic night set-back feature can save some money, but for others, it can result in heat being on when not required.
Efficacy is the capacity or power to produce a desired effect
A radiant wall baseboard heater’s produced heat convects wherever the warmed air takes it, generally up, effectively heating the outside walls & keeping the window inside panes clear from condensation. However, people tend to occupy the space contained between walls, and so a heater that effectively distributes it’s generated heat outwards, to where the people are, can be considered more effective. In addition, wall-mounted unit-heaters concentrate a high heating capacity in a small space. So wall-mount unit-heaters tend to be very effective in places like foyers & bathrooms, where available wall-space is minimal. Downside is the noise. You don’t want a wall-mount unit-heater with a fan beside your reading chair.
Heated floor is also very effective from a human perspective. If your feet are warm, then you are warm. Heat beneath ceramic flooring in bathrooms & kitchens feels wonderful, and definitely adds value to your home. However, the thermal mass of a heated floor is high, and does not lend itself to warming up quickly, so to be of much value, it may get constaltly left on.
The Convectair heaters look like a very good product, but they sure are expensive.
You have an older house with thin exterior walls. If you install one, you can minimize the heat-loss through wall convenction by adding some extra insulation between the heater & the wall. Adding a layer of rockwool, with drywall overtop & some nice wood trim would look great & minimize heat-loss though an outside wall. Otherwise install on an interior wall.
Comparable products, Check out : OCE, OHY, OVE & OVS
Electric heat is presently good value in BC. Present electricity rates, converted to $/GJ, are considerably less than oil or propane. And both oil and propane heating suffers from less than 100% efficiency. However, your house electrical service may or may not have the capacity for adding electric load.
