Time-of-Use Tariffs and Solar Panels: Saving More in NI

If you have solar panels and a battery in Northern Ireland, or are thinking about getting them, time-of-use (ToU) tariffs represent one of the most effective ways to squeeze extra savings from your system. By paying less for electricity when it is cheap and avoiding purchases when it is expensive, you can save an additional £100 to £200 per year on top of your standard solar savings.

This guide explains how time-of-use tariffs work, how to combine them with solar and battery storage, and what NI homeowners need to know to take advantage.

What are time-of-use tariffs?

A standard electricity tariff charges you the same rate per kWh regardless of when you use it. A time-of-use tariff, by contrast, charges different rates at different times of day. The principle is straightforward: electricity is cheaper to generate and distribute when demand is low (overnight, for example) and more expensive during peak demand periods (typically early evening).

A typical time-of-use tariff structure looks like this:

Period	Typical Hours	Rate
Off-peak (cheap)	00:00 to 06:00	10-15p per kWh
Standard	06:00 to 16:00, 19:00 to 00:00	25-30p per kWh
Peak (expensive)	16:00 to 19:00	35-45p per kWh

The exact rates and time windows vary between suppliers and tariff products. Some tariffs offer just two tiers (peak and off-peak), while others use three or more.

The savings opportunity is clear. If you can shift your electricity consumption away from peak hours and towards off-peak hours, you pay significantly less per unit.

How solar and battery storage change the equation

On their own, time-of-use tariffs offer modest savings. Most households cannot easily shift their cooking, heating, and lighting to the middle of the night. But add solar panels and a battery, and the picture changes dramatically.

The ideal daily cycle

Here is how a solar-plus-battery system exploits time-of-use pricing across a typical day:

Overnight (00:00 to 06:00): charge from the grid at cheap rates. Your battery charges from the grid during the cheapest period. Even though you are buying electricity, you are buying it at 10-15p per kWh rather than the 28-32p standard rate. Most modern battery systems (GivEnergy, Huawei, SolaX) allow you to schedule overnight charging through their app.

Morning (06:00 to 10:00): use stored cheap electricity. As you wake up, make breakfast, and get ready for the day, your home draws from the battery rather than buying grid electricity at the standard rate.

Daytime (10:00 to 16:00): free solar electricity. Your solar panels are generating at their peak. Your home uses this electricity directly, with any surplus topping up the battery. During sunny periods, you may be fully self-sufficient and exporting excess to the grid via the Smart Export Guarantee.

Evening peak (16:00 to 19:00): avoid the expensive rate. This is where the biggest savings come from. Instead of buying electricity at 35-45p per kWh during the peak period, your home runs on stored solar energy and cheap overnight electricity in the battery. You effectively dodge the most expensive hours entirely.

Evening (19:00 to 00:00): use remaining battery or standard rate. Depending on battery capacity and your usage, the battery may carry you through the evening. If it runs out, you revert to the standard grid rate until the cheap overnight period begins again.

The savings breakdown

The additional savings from combining solar, battery, and time-of-use tariffs depend on several factors: your battery size, electricity usage, solar generation, and the tariff rates available. Here is a realistic estimate for a typical NI home.

Saving Source	Estimated Annual Value
Standard solar self-consumption	£300 - £600
Battery storage (shifting solar to evening)	£100 - £200
Time-of-use tariff optimisation	£100 - £200
Smart Export Guarantee income	£50 - £100
Total	£550 - £1,100

The time-of-use element alone adds £100 to £200 per year. That may sound modest, but over a 10-year battery lifespan, it contributes £1,000 to £2,000 in additional savings, effectively reducing the payback period for your battery by one to two years.

Smart meter requirements

To access a time-of-use tariff, you need a smart meter. Specifically, you need a SMETS2 (Smart Metering Equipment Technical Specifications, second generation) meter. This is the current standard for smart meters in the UK.

A SMETS2 meter records your electricity usage in half-hourly intervals, which is how your supplier calculates what you owe at each rate tier. Without a smart meter, your supplier has no way of knowing when you used electricity, so they cannot offer variable pricing.

Getting a smart meter in NI:

Smart meter rollout in Northern Ireland has been slower than in Great Britain, but the programme is progressing. NIE Networks is responsible for the metering infrastructure, and NI electricity suppliers are offering smart meter installations to customers. If you do not yet have a SMETS2 meter, contact your electricity supplier to request one. Installation is free.

If you are having solar panels installed, ask your installer about smart meter coordination. Some installers can arrange the smart meter installation as part of the solar project, saving you a separate appointment.

Which NI suppliers offer time-of-use tariffs?

The Northern Ireland electricity market is smaller than the GB market, and the range of time-of-use tariffs is more limited. However, options are growing.

What to look for:

• Check with your current NI electricity supplier for any variable-rate or smart tariff products
• Compare offers from all NI suppliers, as the market is evolving
• Look for tariffs specifically designed for solar and battery owners
• Some GB-based suppliers with NI operations are beginning to extend their smart tariff offerings to Northern Ireland

The tariff landscape changes frequently. When you get solar quotes, ask your installer which tariffs they recommend for battery owners. Good installers stay up to date on the best tariff options and can advise on battery charging schedules to match.

Practical tips for maximising savings

1. Set your battery charging schedule

Every major battery brand (GivEnergy, Huawei, Tesla, SolaX, Fox ESS) allows you to set a charging schedule through its app. Configure the battery to charge from the grid during the cheapest overnight hours. Most systems also have a “solar only” mode for daytime, so the battery prioritises solar charging once the sun is up.

2. Time your high-draw appliances

Even without a battery, you can save money by running dishwashers, washing machines, and tumble dryers during off-peak hours. Many modern appliances have delay-start timers. Set your dishwasher to run at 2am rather than after dinner.

3. Charge your EV overnight

If you have an electric vehicle, charging it during the cheap overnight window can save hundreds of pounds per year compared to charging during peak hours. An EV charging at 7.4 kW for six hours overnight at 12p per kWh costs roughly £5.30 for a full charge, compared to £20 or more at peak rates.

4. Monitor and adjust

Use your battery app and smart meter data to understand your consumption patterns. Most systems show you exactly when you are importing from the grid and at what cost. Adjust your schedules based on real data rather than guesswork.

5. Review tariffs annually

The energy market is changing fast. Time-of-use tariffs that were competitive six months ago may no longer be the best option. Review your tariff at least once a year and switch if a better deal is available.

Is it worth it?

For NI homeowners with solar panels and a battery, adding time-of-use tariff optimisation to your energy strategy is a straightforward win. It requires no additional hardware (beyond a smart meter), no installation work, and no ongoing effort beyond setting up your battery schedule once.

The £100 to £200 in annual savings may not sound transformative on its own. But combined with solar generation savings, battery self-consumption gains, and export income, it is another layer of value that strengthens the overall financial case for your system.

If you are still deciding whether to add a battery to your solar installation, the availability of time-of-use tariffs is one more reason to seriously consider it. A battery without ToU optimisation is good. A battery with it is significantly better.

Ready to explore solar and battery options for your home? Get free quotes from NI installers and ask about time-of-use tariff compatibility.