The past few days have been a welcome break from the longest, driest summer in recent memory. The first cold front of the fall came a little early. That means that last week’s daytime highs in the 90s gave way to highs of just 72F over the weekend. And overnight lows in the high 50s. It’s most welcome.
Julio, our ten-year-old Dogo Argentino mix, finds this change in the weather most invigorating. He’s not the only one. Our air conditioner is getting a welcome break. I woke early one morning to dead silence. The condenser of our air conditioner, which sits outside our bedroom window was idle. Normally, that sort of thing would be cause for concern. Has it failed? Not in this instance. It was simply not required. Just blissful silence.
Being the curious sort, and data driven (addicted?) I checked out how much power the house had been using overnight. The combination of Home Assistant and a Shelly current sensor provides that data.
This bears a little interpretation. Last week we engaged a portion of our annual Halloween holiday lighting. It’s powered via some TP-Link KASA smart outlets set to turn it off at 1am. No point of alight show that no-one will see. That explains the drop in power used after 1am.
Thereafter the house cruises along using just under 400 Watts. That’s mostly tiny, unswitched loads. The fridge, wine fridge, thermostat, keeping the clock on the stove and microwave running. Also, things like Amazon Echo’s and Google Streamer that never really power down. Much of what’s plugged into AC power draws a trickle even when nominally in the “off” state.
An hour before sunrise the holiday lights turn on, for the benefit of those dropping kids at the elementary school across the street. They turn off again at sunrise. As of 1pm today we’d used just 6.93 kWh.
Looking at the prior day (below) I see we used 23 kWh. That’s not the lowest for a complete 24 hour period, but it’s close. When the outside temperature is just below room temperature, and we’re not doing laundry or running the dishwasher, we can eek under 20 kWh/day.
This kind of info was helpful in planning our backup power strategy. We know both the minimum (20 kWh/day) and maximum (93 kWh/day) of power we need. We know that a 9.5 kW generator is more than enough to comfortably sustain the house, which never draws more than 6 kW.
Hope is not a strategy. Knowing is better than guessing.
More recently, a few people have asked me about Base Power, which is continuing to rollout across Texas. Base Power is a retail electric provider who can also provide a battery that serves as a backup power source. In truth, their business has a few aspects.
They’re a retail electric provider. Even without the battery system, you can sign up to purchase power from the company.
They’re a virtual Power Plant (VPP.) Their fleet of installed batteries serves to balance load on the grid. Literally every day they charge the batteries when the wholesale spot rate for power is cheapest. Typically that’s when wind and solar are delivering well. Then they discharge the batteries back to the grid when the spot rate peaks. That’s most often in the early evening when wind & solar are fading even as domestic load is peaking.
This arbitrage game exactly mirrors what grid-scale battery installations do. The big difference is that the VPP is a distributed resource, not installed at one location. Not beholden to one grid interconnect.
In the ERCOT graph of fuel mix, they are part of the Power Storage category shown in red.
Along the way, they provide the homeowner with a short-term backup power solution. Homes with a Base Power battery system will not suffer electrical outages measured in minutes-to-hours.
At point of introduction their battery systems were around 20 kWh. You could opt for two, delivering 40 kWh of local storage. They recently upgrade, such that what they now call the Base Core is a 40 kWh battery. You can still opt for two, if you want.
The question people most often ask is how long will that battery sustain their home during an outage? Base power says that it supports “36-72 hours of operation,” where 72 hours is what you get from two battery systems. Of course, that’s a generalization. That’s all that can be offered without knowing some details of your homes requirements.
Given what know about our home, a 40 kWh battery would last us for perhaps as long as 36 hours on a day like today, when the load drawn is at its minimum. In the peak heat of the summer, with air conditioning running constantly, it would only last around 10 hours.
If we had a significant solar array on the roof the Base Power solution would be even more attractive. We’d charge by day and draw it down overnight. Historically, our home has not been a good candidate for solar. Our roof is not large enough and there’s too much mature tree cover.
The larger problem here in hurricane alley are outages lasting multiple days. Even weeks. How would you fare when the grid was not available to recharge the battery? Would you lean hard on solar? Or would you fire up a generator? The generator inlet is an option on the Base Power system.
I like the idea of using a generator to power the house and charge the battery in the daytime, then leaning on the battery for overnight. That would eliminate tending the generator overnight, and possibly minimize the ambient noise.
I say “possibly” since there’s a very good chance that the ambient noise profile would be defined by what neighbors where doing to get through the outage. We have in the past suffered neighbors using older and very noisy generators.
We are certainly enjoying the cool weather.