Sol Viva

Should I Upgrade My 6.9 kVA Home Supply When Going Solar in Portugal?

John Wallace
Nov 14, 2025By John Wallace


One of the most common questions we hear from homeowners in Portugal is:

“If I install a solar system, do I need to upgrade my home’s electrical supply from 6.9 kVA?”

The short answer is not always, and in many cases, solar actually reduces the need to upgrade.

But as with everything in solar, the right answer depends on how you use electricity and how your system is designed.

Here’s a clear, simple guide to help you understand when a supply upgrade is not needed, and when it might be the right move.

What Does 6.9 kVA Actually Mean?

In Portugal, homes often have one of three contracted power levels:

  • 3.45 kVA: Small apartments
  • 6.9 kVA: Typical villas and townhouses
  • 10.35 kVA+: Large homes with heavy loads

A 6.9 kVA supply means your home can draw around 6,900 VA ≈ 6.9 kW from the grid at any moment before your smart meter trips.

Without solar, it’s easy to hit this limit if you run several big loads at once e.g. Induction hob + oven + AC + pool pump.

Solar changes this dynamic.

How a Solar System Adds “Headroom”

A correctly designed solar system can temporarily increase the available power to your home during the day and at night.

Example:

  • You have a 6.9 kVA grid connection
  • You install a 6 kWp solar system plus a 5kWh battery
  • On a sunny day, your solar plant produces 4–6 kW for hours at a time
  • The battery 2-3kW of power

This means your home can effectively draw:

  • 6.9kW (from the grid)
  • 4–6kW (from your solar)
  • 2-3kW (from your battery)

= 12–16kW available in real time

This significantly reduces the chance of the main breaker tripping.  

Even in the evening, when solar drops, the battery alone can supply 2–3 kW to support peak loads.

Solar doesn’t legally increase your contracted limit, but it increases your real usable power during the day.

When You Usually Don’t Need to Upgrade

With a 6 kWp solar system and a 5 kWh battery, most homeowners are perfectly fine with 6.9 kVA if they:

  • Have 2–3 small AC units
  • Use gas for water heating
  • Have a small pool pump (<1 kW)
  • Run large appliances at different times (normal household behaviour)
  • Heat the pool only during sunny hours
  • Charge appliances (dishwasher/WM/dryer) during the day
  • Don’t charge an EV at full speed at home

And because the battery supplements your grid, your available power effectively increases, smoothing out peaks.

When a 10.35 kVA Upgrade Might Still Be Needed

Even with solar + battery, some homes may benefit from upgrading:

1. You charge an EV at home regularly
Even slow 3.6 kW charging + normal household loads can exceed 6.9 kVA without careful scheduling.

2. You have a large pool heat pump
Pool Heat Pumps draw 2.5–4 kW continuously and have start-up surges.

3. You run 3–5 AC units at once
In peak summer evenings, this can overwhelm the 6.9 kVA limit (solar production is low and battery power may not fully cover spikes).

4. You have an all-electric home
Electric boilers, heat pumps, electric underfloor heating, and multiple heating appliances can create sustained high loads.

5. You use multiple large appliances simultaneously
For example: oven + hob + AC + pool heat pump + washing machine.

In these scenarios, you may not need a higher supply, but it adds comfort and reduces the chance of tripping.

What the 5 kWh Battery Actually Helps With

A 5 kWh battery provides two big advantages:

1. Load smoothing (avoiding overloads)
Batteries support peak loads by supplying 2–3 kW when needed.

Example:

  • Oven (2.5 kW)
  • Hob (2 kW)
  • AC (1 kW)
  • Pool pump (0.75 kW)

= 6.25 kW total

With solar producing 2 kW late afternoon + battery supplying 2 kW, your grid draw is just 2.25 kW, well under 6.9 kVA.

2. Night-time peak support
If you cook dinner or use AC in the evening, the battery helps prevent the meter from tripping — especially useful in summer.

A Simple Rule of Thumb

Use this quick guide:

Stay at 6.9 kVA together with solar plus battery if you:

  • Have 2–3 small AC units
  • Use gas for water heating
  • Have a pool pump under 1 kW
  • Charge an EV at home but on low speed and during the day
  • Cook with either oven or hob (not both at max)
  • Be careful to not run large loads concurrently

Consider 10.35 kVA if you:

  • Charge an EV at higher speeds during the day
  • Run a pool heat pump >1kW
  • Have >3 AC units
  • Use multiple heating appliances simultaneously
  • Have an electric boiler

Final Thoughts

A well-designed solar system reduces grid dependency and helps you stay comfortably within your 6.9 kVA contracted limit.

At Sol Viva, we always check:

  • Your peak load
  • Your appliance mix
  • Your solar potential
  • Your battery options
  • Your day/night usage patterns

…and give a recommendation that balances comfort, cost, and efficiency.

If you’re unsure whether your home needs a power upgrade, Sol Viva can assess your consumption patterns and design a system that fits your lifestyle without unnecessary costs.