Guide to smart meters for homes with a solar PV system

The issue smart meters were invented to solve

Smoothing demand peaks

Electricity demand currently goes in big peaks and troughs. Those peaks are very costly for the utility companies to supply, and are very carbon-intensive too.

The main usage peak is between 5pm and 7pm, when everyone arrives home and electricity-intensive devices such as ovens, kettles, dishwashers and washing machines all suddenly go on simultaneously. The electricity grid has to build generation capacity to be used just to cover these peaks, and a lot of that infrastructure will sit idle outside the peak hours, making it very expensive per unit supplied.

Unused "free" electricity

Equally in the middle of a windy night, there can be more generation capacity from wind alone than demand requires, meaning there is effectively free, carbon-neutral electricity going to waste.

The smart meter solution: pricing by time of day

Smart meter pricing: both carrot and stick

The main aim of smart meters is to encourage us all to smooth out these peaks and troughs in electricity demand. This encouragement is done by price, and there is plenty of carrot and stick being used here.

For example, on some smart meter plans a typical cycle of a washing machine might cost anything from 8 cents to 52 cents depending on the time of day, a six-fold difference in the cost for the same wash.

Good for the planet, as well as your pocket

The expensive times of day are also the most carbon-intensive, too. These demand peaks are mostly met with fossil fuel generation, so the peak hours often produce the most CO2 per unit of electricity.

The cheapest times are generally fulfilled with the highest proportion of renewable electricity. Indeed there are windy nights in Ireland where 100% of the demand is met by wind, and still, there's spare unused wind generation capacity currently going to waste. This effectively means there's carbon-neutral electricity available and going unused. Any units of electricity you use then have just a fraction of the CO2 footprint compared to a peak-time unit of electricity.

What is a smart meter, and how do they work?

Measuring electricity usage in 30-minute slots

Smart meters measure your electricity usage in half-hourly slots, so utility companies know not only how much electricity was used, but the time of day it was used too.

This allows utility companies to set different prices for electricity use during peak hours and electricity used during quiet times. Indeed some smart meter plans have four different rates used throughout the day.

Sending readings to ESB Networks automatically

Smart meters send their readings directly to ESB Networks automatically. No need for any more meter readings, and the end of estimated bills.

Live data, for ESB Networks and for you

Another advantage of smart meters is they can send meter readings back to ESB Networks every 30 minutes. This gives the electricity grid operators near-live data, helping them understand usage and balance the grid. You to can see your usage data nearly in real-time, helping you understand and adjust your electricity consumption.

Recording exported electricity from solar panels

Before smart meters, utility companies just estimated how much electricity households with solar panels might supply back to the grid, and they were paid based on this estimate.

Smart meters measure electricity going in both directions – not only your consumption, but if you have solar panels (or another micro-generation system like wind turbines) then your smart meter will measure the exact amount of electricity you supply back into the grid so you can be paid the correct amount for that electricity.

Note: smart meters are replacing digital meters / day-night meters

Please note that "digital" meters and day-night meters are not the same as smart meters. These will all be replaced as smart meters roll out.

Understanding smart meter plans

With smart meters, each utility company not only sets the rates, but also which times of day are at which rate. This has led to a huge array of tariff options.

A common misconception about smart meters

One common misconception is that you have to have a plan that involves peak rates and off-peak rates when you get a smart meter. That's not true - you can still pick a tariff that charges you one flat rate per unit 24/7. Depending on your usage patterns though, that may or may not be the cheapest way to go.

If you are able to adjust what time you use your electricity-heavy appliances (timers are my favourite tip here), then there are big savings to be made by switching to a plan that offers cheap times of the day.

Here are two utility companies as an example, and you can see just how much the price of a unit varies depending on when you use it.

Example #1: SSE Airtricity smart meter plans

For each plan you can see the price difference compared to the flat 24-hour rate, to give you an idea of the amount of carrot / stick on offer here for adjusting when you use electricity.

Example #2: Electric Ireland smart meter plans

Example #3: Energia smart meter plans

For each plan you can see the price difference compared to the flat 24-hour rate, to give you an idea of the amount of carrot / stick on offer here for adjusting when you use electricity.

These rates above were last updated 19th Oct 2023, include the discounts available at that time, and assume you get both gas and electricity from the same supplier.

The main downside of smart meters

The main downside is just how hard it is to compare electricity plans between suppliers.

Before, you could just look with the supplier with the lowest unit rate.

Now, one supplier might charge more during weekdays, but less at night and weekends. So I now need to know not only how much electricity I use, but when I use it to know which plan is cheaper.

Myself, I used to work in a power station, and now I run a solar company, so I've a reasonable grip on kW vs kWh, usage patterns the like. And still, I find it a fair challenge to know what the best plan for me would be. It is an issue not with smart meters themselves, but with the huge array of plans now available.

There are some tips and tricks (see below for our favourites), and you can see graphs of your own consumption by time of day by creating an account with ESB Networks here.

How to save money with a smart meter

Saving money with a smart meter plan is about picking the right plan, and then adjusting when you use electricity. There's a few simple tricks here.

Tip #1: Focus on the power-hungry devices

A good rule of thumb for picking out the most electricity-hungry devices is heat. If the device involves heating something up, it probably uses a lot of electricity, so should be top of the list to think about.

Some of the most electricity-heavy household devices are:

• Electric showers
• Electric ovens & hobs
• Tumble driers
• Immersion heaters
• Washing machines
• Dishwashers
• Kettles
• Irons & hair dryers

Yes, you could adjust when you charge your mobile phone, but a typical washing machine cycle uses 150 - 200 times the electricity of a typical phone charge, so focusing on these power-hungry devices is key to savings.

Tip #2: Timers are your new best friend

The great news? Most of the power-hungry devices are used intermittently, and often come with in-built timers.

Take your dishwasher. If you press the timer button, so it comes on during the super-cheap 2am slot, well you've just saved 84% on that wash (based on the SSE night boost rate) compared to hitting "go" straight after dinner.

Tip #3: Charging your solar battery / electric car on super-cheap "Night Boost" electricity

This is perhaps my single favourite money-saving tip.

Most solar batteries can be set to charge from the mains overnight at the super-cheap rate (2am - 4am/5am). Then, you can use this stored cheap electricity to run your morning routine. The solar panels can recharge the battery for a second time during the day, so you still get to use your own solar power in the evenings too.

I do this myself. The power I use in the mornings that's coming from my battery now costs me 10.55 cents / unit, instead of the 48.30 cents / unit that it used to. That's a 78% saving.

Electric cars need a lot of power to charge, and most electric vehicles & EV chargers have timers built in. Again a huge saving is available here. A full charge of my EV (Hyundai Kona) would cost me €31 in the daytime. Set the timers to charge at the 2am "Night Boost" rate instead. It now costs €6.75

Picking the best plan: some rules of thumb

That's all about how much you are able to adjust your usage to the cheap times of day. Please take the below as rough ideas only, you'd need to know your own usage patterns to know for sure.

You can see graphs of your own consumption by time of day by creating an account with ESB Networks here.

Got a solar battery / EV, or both?

I would consider a "Night Boost" rate.

The ability to store electricity at that super cheap rate (normally around 1/4 price of day rates), but then use that power during the day is a huge money saver.

You have two big options there to make the most of that very cheap power from 2am-4am/5am, which with a few settings on your inverters & EV charger can give great savings both in euros and in your CO2 footprint.

No? How about lots of white goods with timers?

Here I'd be looking at one of the day / night rates, or perhaps a weekend-based rate if you are a household that tends to be out most of the week then have a big catch-up on washing and everything else over the weekend.

The delayed start function of things like washing machines & dishwashers is a great way to move your usage to the cheaper times of day.

Not planning on any changes? Perhaps a flat rate

If your usage patterns are fixed, and are heavily biased to the day and peak 5pm-7pm hours, then you may still find the best value is in a flat rate usage.

How to Get a Smart Meter

Getting your meter upgraded to a smart meter is free. There are two separate tasks to do here: getting the physical meter replaced, and then changing your plan to a smart meter plan.

Please note that your meter will be upgraded to a smart meter in time anyhow - smart meters are rolling out across Ireland. But, if you'd like yours prioritised, you can request this from ESB Networks.

Task #1: Getting your old meter replaced with a Smart Meter

Note: Smart meters are being installed by ESB Networks, not your electricity supplier.

To request prioritisation, just get in touch with ESB Networks at esbnetworks@esb.ie (and include your MPRN & address).

When I got my meter replaced (summer 2023) there was a 2-month lead time from request to replacement.

Task #2: changing your plan to a smart meter plan

Once the meter is changed that does not automatically change your plan to the right smart meter plan. To do that, you need to contact your electricity supplier.

There is a bit of a delay here. Data needs to be flowing to your utility company before you can change to a smart meter plan, and utility companies generally say that takes around 30 days from when your smart meter was installed before they can change you to a smart meter plan.