More frequent and extended heatwaves across continents imply more reliance on A/C. Hopefully we will see more RnD, more products, cheaper solutions.

For home cooling, A/C is the primary solution and default solution for Singapore residents, with a running cost ≈ $0.25/hour/household, i.e. slightly below 1kWh / hour / household. However, other costs are easily neglected —

1. (similar to car ownership) dependency
2. (similar to car ownership) maintenance costs like noise, leak, poor cooling…
3. carbon footprint

Therefore, I see ROTI of research/experiment with natural cooling solutions.

— solution: fan
— solution: wet t-shirt. Heat center is the upper back
During Sleep?

— solution: frequent showers, or wet towels by bedside. I developed this solution in #2-1173

==== Estimating A/C cost$/hour .. Imprecision is the reality, the backdrop. We will focus on kWh. Then we estimate SGD cost per hour.

https://www.channelnewsasia.com/commentary/air-con-unit-electricity-energy-carbon-emissions-climate-change-1339326 says “A standard 2 kilowatt AC unit .. can comfortably cool a room of up to 20 sqm.” My model (MSY-GE10VA) is 10,000 BTU, average 2.5 [1.1-2.5-3.5] kW per unit. Vendor call center gave me a best-effort estimate, with sweeing assumptions to simplify many many factors

• condenser (outdoor unit) is the real energy hog. For a system 4 set to 23~25 degrees, the condenser would consume 2.4 kW at 100% capacity. This is probably signified by double-green light on some of the four indoor units.
• If every indoor unit shows one green light only, then condenser is running around 60% load, consuming 0.9 kW only.
• If only one unit is running, and showing one green light, then condenser is perhaps running 25% load.
• Initial cool-down drives the condenser harder than maintaining at target temperature. Condenser can even reach 0% load for 10 minutes if all rooms dip below target temperature.
• high fan speed also drives the condenser to higher load

Verified fact: my home uses 230 kWh/month or close to 8 kWh/day. (#2-1176 was 300 kWh/month, presumably due to boy’s additional A/C usage.)

Assuming average 5/day .. aggregate across my 3 rooms .. we use about 4kWh+/day, or more than half the household power consumption.

(In comparison, my fridge uses 27 kWh/month equivalent to a 37.1W lamp, according to manufacturer.)

NEA claims “Air-conditioners consume the bulk of a household’s electricity bill. A fan uses less than 1/10th the electricity of an air-conditioner”

Q: when an A/C unit is only keeping a room (at 24 degrees for eg), does it use less electricity than actively cooling it down?
A: I think so, but without evidence. If no air leak, then the room would tend to stay cool, or lose cold air slower.

— Many websites underestimate the variation in manufacturers’ power ratings (0.3 to 3 kW!) and usage hours (1 to 10!) per day.

One Sgp site claims “On average, an air conditioner’s usage costs $0.25 to $0.35 per hour (per unit). This depends on the size of your space and what type of air conditioner you are using.” I think this assumes 1.0 kW for a single unit.

one site claims “In Singapore, the average household spends $30-$45 per month on electricity for an air conditioner.” but this is overestimate for my family.
* When we were on SingPower, we were probably paying $70~90/M for all electrical appliances.
* Now we are on PacificLight, we are spending $55~70/M for all electrical appliances.