I needed to make the same decision last winter.
I have a couple of IPs that I have set up as share accommodation. One of them is an seven bedroom house with 1 bedroom granny flat and inground, solar heated pool. Our contract with the tenants is that we pay all utilities, including the first $1200/qtr electricity. If they use more than that, then we split the difference equally between them.
We have only had this particular property for about 1 1/2 years (one winter), but needed to install heating last year as the property only came with ducted evaporative cooling (very effective in Adelaide) and a modern gas fireplace to the main living area (not very effective in heating the whole house). Given the size of the house, I considered many alternatives: reverse cycle A/C, ducted gas, gas room heaters, electric room heaters, electric heat banks, gas heat banks, geothermal, gas powered central heating, pretty much everything.
I am not in the industry, so please take what I so below with due consideration.
After speaking to many "experts" (albeit many of whom had a vested interest), the consensus seemed to be:
- Regardless of the method of delivery, electric room heating is an inefficient method of heating. The only ways to minimise this are to use thermostats, or to use heat banks, which can (when certain conditions are met) be connected to off-peak power, thus reducing the cost.
- Gas is more efficient, but has a significantly higher up-front installation cost
After much deliberation, we chose the NOBO heaters because:
- They are cheap to install (just need a power point)
- They can be installed with an optional "student" controller, which automatically turns the heater off after approx. 2 hours. This prevents tenants simply leaving the heaters on. This option also provides a more limited temperature range (24C max from memory), so tenants can't set the thermostats to ridiculous temperatures.
- They are thermostatically controlled. This, combined with a max 24C set point, means they should cycle to reduce power consumption
Ducted gas came a close second, but this is a two storey house, and supply and install of this was going to be WAY too expensive.
Our experience so far is that power bills are about $200 - $300/qtr more than in summer. To put this in perspective:
- There are 8 tenants in the house who don't have to pay for the majority of their power.
- We have installed a 2000W NOBO heater in each of the 8 bedrooms
- Our summer bill for the house is usually around $1000/qtr. This pays for the pool (pump is running 6 - 8 hrs per day), evaporative cooling, 2 modern split R/C A/C wall units, 8 laptops, 4 - 5 big LCD/Plasma TV's owned by the tenants, 4 fridges, etc. etc.
- Our maximum winter bill for the house has been $1300/qtr. This pays for the pool (pump is running 3 - 4 hrs per day), 8 x 2000W NOBO heaters, 2 modern split R/C A/C wall units, 8 laptops, 4 - 5 big LCD/Plasma TV's owned by the tenants, 4 fridges, etc. etc.
So, the difference is evap cooling in summer vs. NOBO heaters in winter. Given the cost of running evap cooling is negligible (say $100/qtr - a guesstimate on my part), this would equate to around $300 - $400/qtr for 8 x 2000W NOBO heaters. Or around $50/qtr for each 2000W NOBO heater
Considering these factors, this doesn't seem too bad to me.
Oh, and I forgot to mention that the total living area of the house (living, family, kitchen, bedrooms, etc.) is around 350m2 andthe bedrooms are around 20m2 each.