More solar. No panel upgrade. No change order.
Every Watts Up system over 40 amps uses Enphase Power Control, a code-recognized safety system that lets a full-size solar array live on the 200 amp panel you already have. Here is what it is, where the old limit came from, and why the "curtailment" story you may have been told takes thirty-two microwaves to come true.
The hardest a house ever works, and the pile of microwaves it would still take on top of that to make Power Control act. Hover to pause, click to hold it there. The steps are written out below.
Your House Is A Quarter Of The Line. Then Add Twenty Microwaves.
- Power Control can only act above one line: 200 amps on the busbar, 48 kilowatts. Below it, it does nothing at all.
- An ordinary evening, dinner on the stove, TV on, dryer running: about 4 kilowatts. Two blocks of twenty.
- The coldest morning of the year in an all-electric house, heat flat out, hot water recovering: about 12 kilowatts. A quarter of the line.
- Charge the car at the same time: 19 kilowatts. Not even halfway. That is the hardest a house ever works.
- So start adding microwaves on top of that. Five. Ten. Fifteen.
- Twenty microwaves, all on high, at the same instant. Now you are at the line.
- Only now, and only for this moment, does Power Control trim the solar. The grid covers it. The house notices nothing.
- Unplug one microwave and it is over. That is the entire curtailment story.
Your Panel Has A Speed Limit. Somebody Guessed It.
Inside your electrical panel are two copper bars, the busbar, that every breaker clips onto. Grid power comes in through the main breaker at the top. Each circuit takes what it needs on the way down. The bars are rated to match the main breaker, usually 200 amps, and the main breaker is what protects them.
Solar adds a second source on the same bars, through its own breaker, at the other end. The main breaker cannot see that current, so the electrical code caps how much you are allowed to add. In Canada the cap is 125 percent: the main breaker plus the solar breaker may total 250 amps on a 200 amp bus. That leaves room for a 50 amp solar breaker, which the code lets you load to 40 amps continuously. Forty amps at 240 volts is 9.6 kilowatts, about 26 microinverters. That is the line. The American version of the rule says 120 percent, which is why the trade calls it "the 120 percent rule" on both sides of the border.
Where did 125 come from? Not from your panel. Nobody measured anything. A code committee picked it as a comfortable margin, reasoning that houses almost never load their panels anywhere near the rating. The American committee picked 120. The Canadian one picked 125. Same copper, different room. It is a probability judgement with a percent sign on it.
The rule's own fine print tells you what the committee really believed. The solar breaker must sit at the opposite end of the bus from the main. With one source at each end and every load in between, no point on the bus can ever carry more than the bigger source, and the bigger source is the main breaker. The percentage is blanket insurance for panels that are not laid out that neatly, and for the day someone moves a breaker.
When a system needs more than the margin allows, the old answer was hardware. A bigger busbar. A dual lug meter base so the solar can connect ahead of the main breaker. Or a full service upgrade. Thousands of dollars, a utility disconnect, a day without power, and none of it makes a single extra kilowatt-hour.
Replace The Guess With A Measurement.
Power Control is the same rule, enforced by measuring instead of assuming. Three parts, all of them already inside every Enphase system we install.
Measure
Current sensors clamp around the conductors feeding your panel and watch every amp flowing in and out, continuously. Not a calculation on paper. The actual current, right now.
Decide
The IQ Gateway, the same device that runs your monitoring app, compares the live current against your busbar's rating in real time.
Trim
If the bus would ever exceed its rating, the gateway tells the microinverters to back off, by exactly as much as needed, for exactly as long as it takes. Then they come straight back.
This is not a loophole. Rule 64-112 of the Canadian Electrical Code says the breakers on a busbar may exceed the 125 percent limit when equipment monitors and limits the current so the bus cannot be overloaded. Nova Scotia adopted the 2024 edition of that code on July 2, 2024, without amendment. Enphase Power Control is a listed power control system, and it is permitted and inspected like every other part of your installation.
It also does something the hardware answer cannot. A power control system is listed to fail safe: if the controller ever lost contact with the microinverters, they would fall back to a limited output rather than carry on unchecked. A bigger busbar protects you from exactly one thing, and only until someone moves a breaker.
The Code, In Writing
In a dwelling, the breakers feeding a busbar may total 125 percent of its rating, with the solar breaker at the opposite end from the main.
Any size of system may exceed that limit where equipment monitors and limits the current so the busbar cannot be overloaded. That equipment is Power Control.
Nova Scotia adopts the 2024 Canadian Electrical Code with no amendments (Provincial Safety Bulletin 35).
Enphase Power Control is a listed power control system, permitted and inspected like every other part of your installation.
Forty-Eight Kilowatts Is A Massive Amount Of Power.
Power Control can act in exactly one situation: the grid and the solar are both pushing into the bus at the same moment, and together they would exceed the bus rating. The bus only carries what your house is using, so for the bus to hit 200 amps your house has to be pulling 200 amps. At 240 volts that is 48,000 watts. Not for a split second when the fridge kicks on. Sustained. Here is what 48 kilowatts actually looks like.
Thirty-two microwaves, all running at full power, at the same instant, in full sun, before Power Control trims a single watt.
1,500 W microwave at 240 V = 6.25 A
200 A × 240 V = 48,000 W
48,000 W ÷ 1,500 W = 32 microwaves
Every one of these on high, at once, with the sun out. Then, and only then, the software does its job.
Your house does not come anywhere near it. An ordinary evening, dinner cooking and the dryer running, is about 4 kilowatts. The coldest morning of the year in an all-electric house, heat flat out, is about 12. That is a quarter of the line, and it is the hardest a house ever works. Charge the car at the same time and you are still not halfway. From there you would need to add twenty microwaves, all on high, at the same instant, before Power Control trims a single watt. And the coldest morning of the year is not when the sun is out.
And if it ever did happen? The microinverters ease off for a few seconds, the grid covers the difference, and nothing in your house notices. The energy involved is worth a few cents. Set that against the thousands of dollars a meter base or busbar upgrade costs, plus a day with your power off to install it.
What A "Curtailment" Warning Actually Tells You
When a salesperson tells you Power Control will "curtail your performance", they are telling you one of two things. Either they do not understand how the panel on your wall works, or they understand it perfectly and are counting on you not to. In both cases the motive is the same: the string inverter they are selling cannot do this, so they need you to be afraid of the equipment that can.
If Power Control cost our customers real production, we would not use it. We publish the production of every system we have ever installed. Check.
The Sales Script, And What Is Actually True.
"Any system over 40 amps needs a dual lug meter base. Anyone who says otherwise is lying and will hit you with a change order later."What is true
The Canadian Electrical Code says otherwise, in writing, and Nova Scotia adopted it without amendment. Since 2024 every Watts Up system over 40 amps has been designed, permitted and inspected with Power Control instead of a meter base.
The price on your proposal is the price. There is no later invoice for a meter base because we do not install one. And you do not pay us a cent until your system is commissioned and approved, so there is nothing to change-order against.
"Power Control curtails your production. That is the trade-off for skipping the upgrade."What is true
In theory, for a few seconds, while thirty-two microwaves run in full sun. In practice, never. The grid covers any trim, your home loses nothing, and the few cents of energy involved would not pay for the first screw of a meter base.
There is no trade-off here. There is a measurement replacing a guess, and a company that would rather you did not know the difference.
We Sold Meter Bases For Ten Years. Then We Stopped.
For a decade we did what every installer still does: busbar swaps, dual lug meter bases, service upgrades. It was real revenue and we were good at it. When Enphase released Power Control, we were the first installer in Nova Scotia to use it, and we dropped the upgrade work the same season, because our customers no longer needed it.
That decision costs us money on every large system and saves you money on every large system. It is now being used against us by companies selling inverters that cannot do what ours do. We would make the same call again, because the point was never the revenue. The point is that you get the best equipment, installed the least invasive way, at a price you can verify before we ever speak.
Measuring Beats Guessing. It Always Has.
Power control is not a solar workaround. It is how every piece of electrical hardware is learning to share a panel. The American code gave power control systems their own article in its 2026 edition. The Canadian code already recognizes them. EV chargers, heat pumps and batteries are all arriving with the same idea: watch the current and manage it, instead of ripping out a perfectly good 200 amp service every time a home adds a load.
A rule written as a percentage was the best anyone could do in the 1980s. A rule enforced by a sensor is simply better. We would rather sell you the better one.
Forty Years Of The Same Rule, Getting Smarter
- 1987The American code first lets a home's breakers exceed the busbar rating, by 20 percent. A committee's margin, not a measurement.
- 2008The same allowance is extended from homes to every solar system.
- 2021The Canadian code adds the escape hatch: any size of system, if equipment monitors and limits the current.
- July 2, 2024Nova Scotia adopts the 2024 Canadian Electrical Code, no amendments. Rule 64-112 4) g) is the rule here.
- 2026The American code gives power control systems their own article. Measuring becomes the default.
Power Control, Asked And Answered.
No. It runs on the IQ Gateway and the current sensors that are already part of every Enphase system we install. The gateway is the same device that feeds your monitoring app. There is no extra box on the wall and nothing extra on the invoice.
Yes. Rule 64-112 of the Canadian Electrical Code permits the sum of the breakers on a busbar to exceed the 125 percent limit when equipment monitors and limits the current so the bus cannot be overloaded. Nova Scotia adopted the 2024 edition of the code on July 2, 2024, without amendment. Our Power Control systems are permitted and inspected like every other installation.
Power control systems are listed to fail safe. If the controller ever lost contact with the microinverters, they would fall back to a limited output rather than carry on unchecked. The hardware answer, a bigger busbar, has no such safeguard against the day somebody moves a breaker.
The same system manages battery output, so a battery and a large array can share your panel too. It can also hold an EV charger back when the rest of the house is busy so the main breaker never trips, which is the same idea applied to a load instead of a source.
Exactly what everyone else still does: busbar swaps, dual lug meter bases and full service upgrades. Ten years of it. When Power Control arrived we were the first installer in Nova Scotia to use it, and we dropped the upgrade work the same season because our customers no longer needed it.
Almost certainly not. For it to act at all your home has to draw more than 200 amps while the sun is out. If it ever did, you would see a dip of a few seconds, the grid would cover the difference, and the energy involved would be worth a few cents.
The Technical Version
Battery oversubscription, import and export limiting, EV charger load management: the full engineering write-up of what Power Control does on an Enphase system.
Read the technical article Unlocking Greater Solar Potential with Enphase Power ControlSize It For Your Roof, Not For Your Panel
Price the system your roof can hold, with the equipment that can live on the service you already have. No pressure and no salesperson.
Go Quote YourselfSo, thinking about solar? Let's talk
The quickest way to get a quote is to fill in our contact form.
Get in touch