240-V Heaters vs. 110-V Heaters

Since you say that you have both 120 and 240 voltage available, I'd recommend using the higher voltage heaters just for the sake of load balancing. Since most power grids regulate their voltages so that the difference between the two split phase voltages remains a constant 240VAC, the cycling of your heaters will not significantly affect your other circuits. But a 120VAC heater load addition on one split phase line will sag that side to say 105VAC. The other split phase line will be boosted to 135VAC, 105+135=240. This is an exaggeration to make a point. But if all of your heaters sit on one split phase then this may not be an exaggeration.

Let's keep it simple...(sorry it takes up more than 2 lines of text to reply ) This reply is intended to summarize it all.

1. Select your heater capacity based on heat output first (in kW or Btu/h). You need to calculate how much heat you need in the particular space you are trying to heat. This has NOTHING to do with the voltage - it has to do with:

a)the desired temperature of the room, and the outdoor temperatures on the "design day", the coldest outside temperature you would expect (Refer to Building Codes, ASHRAE, Weather data, a local contractor or supplier),

b) the quality of construction of the room (ie how well insulated the room is, and how much air leakage there is into/out of the room)

c) and how large the room is (area of exterior walls, area of floors above unheated spaces, areas of windows, doors and skylights)

2. Check available voltages at your site (115 v, 120 V, 208 V, 240 V, etc...)

3. Don't forget - you are installing the heater for comfort, therefore the heat output is the primary consideration!

4. Typically you should select a hard wired heater with highest practical voltage at your location. Depending on the actual current drawn by the heater, this may allow for smaller wire and breaker sizes, which may be less expensive and easier to install. If you have several heaters installed, try to balance the loads as much as possible to minimize system imbalances (see previous responses).

5. For residential buildings (and other smaller buildings) you will likely pay the same amount to heat the space at any voltage.

6. In larger buildings where you may have "demand charges" the same applies - you pay for the energy (heat) you use (kWh), and the associated demand (kW). No power factors penalties apply since electric heaters are resistance devices (primarily) (power factor = 1 and kW~kVa in this case). If power factor charges apply, your PF penalty cost may actually be lower because of the heaters helping correct for other low PF devices, but your energy and demand charges would still increase.

7. Note that heater "temperatures" are a function of the design of the heater element and of the cabinet/enclosure. For residential, especially with seniors or children, and where curtains or other combustibles may be present, consider "low Watt density" which gives you less heat per unit area or length of heater, and lower air and heater surface temperatures (these are also slightly bigger, longer units). Maintain clearances recomended by the manufacturer in all cases!

8. Splurge and spend some money on a good quality low voltage programmable thermostat compatible with your heaters, and program it to 'set - back" (lower) the thermostat setting when you don't need as much heat (night time, while you are at work, etc..) THIS WILL SAVE ENERGY, SAVE MONEY, REDUCE greenhouse gases and pollution (where electricity is provided by coal/gas/oil/hydro plants). Your investment in a good thermostat will pay for itself in very little time (depending on how cold it is where you live)

9. Avoid "plug-in" or "portable" heaters if at all possible! Too many risks due to tripping, overheating cords and circuits, risk of tipping over the heaters etc...

Good Luck