For starters, yes, we have A/C and it works. I installed the first phase of my PV system last week and have been trying to go solar-only during this heat wave. Unfortunately, I only budgeted for 3 KW of solar in the first phase of this project, and the central A/C is about 3.5 KW. That means I can run the A/C fine during the day - drawing the difference from the batteries and charging them back up when the A/C cycles off - but at night, it's a straight 65 amp draw from the batteries. Due to the current heat wave, its also running more than it normally would, so the PV is struggling to keep the batteries up.
S.O. and I spent yesterday afternoon and evening downstairs in the basement where it was nice and cool and just turned off the A/C. It was about 11 PM when the movie we were watching finished so we decided to call it a night. Came upstairs, and it was 85 degrees. Yikes.
Rather than run the A/C to pump out almost 20 degrees of accumulated heat, we just opened all the windows hoping it would naturally cool down overnight and the A/C could cool it the rest of the way down in the morning.
We've also got a little 5,000 BTU (450 watt) window unit in the bedroom, so we brought the dogs in with us, closed the door, and turned that on. It's pretty easy on the house battery, and we slept comfortably.
When we got up around 6:30 this morning and opened the bedroom door, it was like walking into an oven. Despite the outside temp dropping to 70 degrees overnight, the house only cooled 2 degrees from 85 to 83. S.O immediately caved and turned the A/C on (don't blame him at all) and it's been been running constantly for about 2 hours now pumping out the accumulated heat. House battery is down to about 38% as of this writing, and the sun is just starting to hit the roof panels in useful amounts.
Today's forecast is 99 degrees and afternoon thunderstorms, so I may have to cave and switch back to utility power for the rest of the heat wave (the rest of the weekend is supposed to be cloudy and hot).
Lessons learned:
- Add more PV to the roof ASAP
- Buy S.O. something nice for going along with my solar-only shenanigans this week
- It would have probably saved energy in the long run to have run the A/C the whole time at a higher temp than leaving it off and then pumping out about 14 hours of accumulated heat.
- Updating the house's insulation is probably the next project I need to plan
Consider a whole house fan if it’s 85° inside and 70° outside…
We can run the HVAC in fan only mode, and it doesn't seem to help much for cooling with the windows open. Just moves the same air around unless there's a breeze outside pushing outside air in/out.
We used to have a pair of window fans we put on opposite sides of the house, one pushing and one pulling, but those both failed in the last few years and we never replaced them (Why do window fans cost ~$60?! lol) Those worked great, so I guess I'm just gonna have to pay the ridiculous prices and replace them.
Air conditioners are designed to move the heat from inside to outside, not the air. So an HVAC fan doesn't pull air in from the outside, it just recirculates the air in the house across the evaporator, which in "fan only" mode is turned off.
Window fans are an excellent idea, it's the only cooling method I need here in New Mexico. That, plus an insulated house. I run the fans for a couple of hours in the early morning when it's coolest, and then close up the house. It only gets up to 85F by the afternoon, and with <15% humidity, that is comfortable.
I think he's referring to whole house fan that pulls in air from outside and blows it into the house
I was picturing an attic fan that pushed the hot air up and out so fresh air is drawn in the windows.
Yup, that's it.
I have a whole house fan and I highly recommend it. Our AC use went down 80%. Gets us comfortable most nights. They’re not too bad to install, a few thousand.
We were using window fans before and it’s just a pain in the ass to have to turn them on individually every night. Also they block quite a bit of your view/natural light. But, using them to see if it works to bring your house temp down is a good strategy to see if a house fan is worth the investment.