How important are buyback rates for solar panel ROI?
Chasing buyback rates while ignoring winter peak prices is how good solar savings quietly disappear.
Everyone’s talking about buyback rates.
Meridian this. Octopus that.
And yeah — buyback rates matter.
But most people are obsessing over the wrong side of the power bill.
Because while everyone’s chasing an extra few cents for exported solar, they’re ignoring what they’ll still be paying for grid power on cloudy days, and during winter evenings — when solar simply can’t keep up.
And here’s the uncomfortable truth:
Solar is unlikely to cover your big winter loads.
What solar actually does well (and what it doesn’t)
Solar is brilliant at smashing summer power bills.
Even without a battery, many homes see close to 90% off their monthly bills.
Winter is a different beast.
Even with a battery, solar generally:
Reduces winter bills by 40–50%, not 100%
Leaves you buying a decent chunk of power from the grid
Especially between 5–9pm, when families actually use electricity
So once you install solar, it becomes critically important that the power you still buy from the grid — mostly in winter — is priced sensibly.
The buyback trap
The highest solar buyback rates come from retailers like Octopus and Ecotricity.
Sometimes their overall pricing stacks up nicely. And sometimes it really doesn’t.
Consumers are signing up to these plans in droves; mainly motivated by the high solar buyback rates.
Compared to the flat “anytime” pricing offered by much of the market, these plans tend to come with peak rates 30–40% higher than what you'd pay at the same time on an 'all the time / anytime' rate. IE; 50c between 5pm to 9pm with a 'peak / off peak plan' but only 35c on an all-the-time plan.
That would be fine... If your solar and battery could actually cover your winter evening usage. But most solar systems can't. So consumers are left buying peak power at 50c per kWh, when they could be paying 35c per kWh.
When peak pricing doesn’t matter
(The seriously oversized system that consistently generates enough for 7am - 9pm in winter)
Let’s say your home uses 12,000 kWh per year.
Ballpark numbers:
1,600 kWh/month in the 3 coldest months, and around 800kWh/month in the 9 warmer months.
That’s about 50 kWh per winter day
Around 35 kWh of that is likely used between 7am and 9pm
Unless your roof is a perfect 35° north-facing unicorn, you’d need roughly:
17.5kW of solar (35+ panels)
A 20kWh battery
Cost? Around $50,000. And this system would handle peak pricing nicely.
But it would also:
Smash into export limits in summer, unless your home is 3 phase.
Waste energy because of the buyback limits
Leave a huge hole in your pocket or home equity.
The upside?
You'd be able to dance around those peak rates like they're the piggy in the middle.
And after 9pm, you'd enjoy the 'super off peak' or 'night rates' — which can be 30–40% below the standard anytime rates.
Sounds great, but reality is - 12,000kWh of usage is typical. $50,000 is not.
And chances are, you're not looking to spend $50,000 on solar?
When rates really matter
(The system most people actually get)
Most homes install solar to:
Eliminate summer bills
Cut winter bills by 40–50%
That means during the coldest three months, you’re still buying roughly half your power from the grid.
So if your system isn’t covering winter evenings (it probably isn’t), then why on earth would you pay 50c/kWh when you could be paying 35c/kWh?
This is where we hear the same line over and over: “We use most of our power in winter evenings and want solar + a battery to ensure a warm house without the bank-breaking power bills.”
And our response is always: “Cool. Solar can help, and let’s make sure you don’t get ripped off during those peak hours.”
Sometimes we recommend those peak / off peak power plans - because often the savings equation works in your favour, even during winter. But that's not the rule. If a solar company is out there pushing one power company over another, without applying some serious thought to the rates you are on now, and the rates you'll be on with solar, you have to ask -
Does this solar company truly understand how changing power companies can affect my month to month energy costs?
“What about charging the battery from the grid?”
Good question.
In practice? It quietly destroys your battery warranty.
Even the latest Tesla Powerwall states that once you charge from the grid:
You lose the unlimited cycle / 70% capacity guarantee
You’re capped at 10kWh of total daily cycling
Exceed that, and your warranty ends once you hit 37.8 MWh of throughput
Do the maths:
37,800 kWh over 10 years
≈ 10.3 kWh per day
Increasing the tire-wear on your solar battery from grid charging may decrease your power bills by a further 10%, but you can also be certain:
Grid-charging your battery reduces its lifespan and its warranty.
Better to design a system with a reasonable evening power price in mind so Peter doesn't get a chance to rob from Paul.
The final word
If you’re like most people, your home barely uses power while you sleep. So on an anytime rate plan, don’t stress about the ~35c anytime rate.
When you’re earning 17–20c on exported solar during the day, the real win is knowing your 5–9pm power price isn’t undoing all that good work.
Because remember:
In winter, solar systems perform at roughly half their summer output
At the same time, homes often use twice as much energy
Get the winter evening rate right — and the buyback rate becomes a nice bonus, not a trap.
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