RESOLVING THE LEDGER
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Follow ZDNET: Add us as a preferred source on Google.ZDNET's key takeawaysBatteries let you store and timeshift power.They can store solar-generated power or cheap, off-peak power.To make this work, you need a TOU tariff with a decent peak/off-peak rate spread.Last week, I traveled to London to see some new products EcoFlow is releasing now that plug-in solar is set to become legal here in the UK. But what struck me was how I feel that pure plug-in solar has already been superseded by hybrid systems offering greater potential for savings.Also: You're charging your phone all wrong: 6 common myths, debunkedDon't get me wrong, I still think there's a place for pure plug-in solar systems where you take solar panels, hook them up to a microinverter, and feed that power into your system to handle some of the energy usage during the day. The problemThe problem, in a nutshell, is a mismatch between household energy use and peak solar energy generation. The average household's power usage peaks twice a day, morning and evening, with a trough between the two. This trough, rather annoyingly, coincides with the single solar energy-harvesting curve, which peaks at midday, a time when most people are out of the house. Also: I tested this backup power station during a real blackout - don't make my mistakesThose of us who work from home or outside traditional hours will win in this scenario because we're there to make maximum use of the power, but for the majority who go to and from work humming Dolly Parton's "9 to 5," this isn't the optimal setup. Sure, solar can carry a fair amount of that daily base load, and it's a step in the right direction when it comes to energy independence, especially if you live in sunnier parts of the country. (Note: Base load is the stuff that's always on -- refrigerator, Wi-Fi router, chargers, and appliances left on standby.) However, there's a limit to solar's effectiveness. The allowable size of a plug-in solar setup -- 800W for Utah and in European countries where it's allowed, up to 1,920W in Colorado -- isn't much, and even under perfect conditions, won't be enough to give you energy independence. Not by a long shot.Time-shifting power - no solar panels neededIdeally, people want a way to capture that power during the day, when it's abundant, and time-shift it to times of day when it's needed. For that, you need batteries. And those batteries can not only store solar power but also be charged from an outlet. In fact, if you have a time-of-use (TOU) or time-of-day (TOD) power tariff where electricity costs less during specific periods, you don't need solar panels. You fill up the batteries with cheap, off-peak power to use during costlier peak periods.Does time-shifting power make sense?One question I get a lot is whether, even with a TOU or TOD rate, it makes sense to fill a portable power station using AC. After all, there are losses every time you charge up a unit, and more losses when you discharge. Don't these losses mount up? How does the math work out for real-world energy prices?Also: I tried a solar-powered AirTag alternative that lasts 2 years - and looks like my Apple WatchWell, I did the math...A portable power station is a battery pack with an AC-to-DC charger and DC-to-AC inverter. Every time power is shifted through one of the parts of the power station, there are losses due to heat during charging and discharging, battery chemistry inefficiencies, and standby drain. The average round-trip efficiency (grid AC into the battery, then out via AC to your load) is in the range of 80% to 90%. This means that for every 1 kWh you draw from the wall outlet, you get 0.8-0.9 kWh of usable AC power back out.This is why you want to store power when prices are low and use it when they're high. And even then, there are losses that eat into your gains.Let's look at a real-world example based on Con Edison prices. Currently, prices are as follows:Off-peak prices: $0.0522/kWh (all hours outside 8 a.m. to midnight) Peak in summer (Jun. - Sep.): $0.2786/kWh Peak in winter (Oct. - May): $0.1711/kWh Also: How much I saved on electricity after months of using backyard solar panels - and my most effective setupI have a 12 kWh "Tower of Power," and if I filled it with off-peak power, I'd need to pay for 15 kWh (this accounts for losses), which would cost $0.783. This would get me 12 kWh of power, which would cost me $3.3432 to buy in summer and $2.0532 in winter.So, each refill has the potential to save about one to two and a half bucks a day. If I took a more modest 3 kWh setup, that would need 3.75 kWh to fill, costing $0.19575, and get $0.8358 worth of summer power, and only $0.5133 of winter power. Here, the savings are down to $0.30 to $0.60 per day. All this is before any customer charges and surcharges start eating into your savings. I think it's vital that you check the math and work out the savings for yourself.Oh, and this is all before you consider the cost of the portable power station and any solar panels, which can be considerable.Is it worth it?People who buy a basic plug-in balcony solar setup will be looking at it purely from a savings perspective. These systems start at around $300 for a 180W system, going up to $1,500 to $2,000 for 800W setups. Throw in a battery (and a smart controller and an energy meter), and the costs go up. The 5,024Wh Stream systems that EcoFlow had on display cost in the region of $2,000 and had an installation charge on top of that, close to $1,000. That's a fair chunk of cash to make back, and that's without adding more expansion batteries (the Stream systems are expandable to a massive 90kWh) or solar panels, line items that will push the price up considerably. To make your money back here you're going to have to make sure you're on the best possible energy tariffs, and make sure you work the system. Also: You've been using your power bank wrong, and airline rules make that obviousFortunately, the system is smart, and every...
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