Is a Night Rate Meter right for me?
Since 2015 Tipperary Energy Agency has been supporting homeowners decarbonising their homes using heat pumps. We are often asked if it makes sense to install a night meter.
What is night rate meter?
A night rate meter is a meter that affords the user lower rate electricity during the hours of 11pm-8am (End October to end of March), and midnight to 9am in the summer months. The reason that the time changes from summer to winter is based on not resetting mechanical clocks when the times change! This lower night rate costs are balanced by a slightly higher day unit cost and slightly higher standing charge.
When does it make sense to have night rate?
If you use the 4200 national average units (kWh) per annum, then you will have the same costs at 27% usage during night rate hours or 3.16 units during the night hours. Assuming a minimum load of about 200Watts, the average home would use 1.8kWh/ units at night, so one would have to actively use about 1.4kWh extra units on night rate.
However, when someone installs a heat pump (assuming about 4000units used for heating), the night rate meter would make sense if you had your heating on at any point during the night hours or run your hot water cycle at night. This would be about 20% of your overall usage at night or 4.5 Units during the night hours on average (an additional 2.7 Units at night).
We typically see 35%-45% usage at night time with homes with heat pumps (and in some cases PV). And the use of a night meter would save €150 – €250 per annum. This would represent 10% – 20% depending on how well you use your home appliances and heat pump.
At the time of writing that following day/ night vs standard Electric Ireland Tariffs (largest market share for info only and do not include direct debit and online billing discounts):
Commission for Regulation of Utilities Q1 2018.
Note many, if not all the providers offer introductory discounts that apply for new customers that are not referenced in the above graphics.
The below analysis is based on the Rural Tariff, but there is little major difference, and would most likely be included within the two lines.
If one uses only a Heat pump to supply hot water (assumed 10kWh of hot water at a cop of 2.5) at night, and an average base load of 200W from standby appliances, one would use 5.8kWh. Any extra appliance usage or heating usage would likely drive significant savings in terms of using night rate.
What about an Electric Car?
If you use your EV charger at home and at night, it makes a lot of sense to have a night rate meter. If we assume 18000kms per annum, 15kWh/ 100kms and 80% home charging at night, then one would utilise 6 units per night. Noting that one only needs less than half this to break even, it makes a lot of sense.
Does a PV installation make a difference?
Yes, a PV array generates in the day and therefore the slight increase in day rate costs have a little lower impact, and it usually results in a higher % night rate.
Is this the same for all suppliers and tariffs?
In principle it is similar, however the % night rate required changes per supplier and the heavily discounted introductory tariffs need a little higher % night to break even. This would equate to 24% break even Vs 20% on the standard Electric Ireland tariff for a home with a heat pump.
So is this right for me?
If you have a heat pump or an Electric vehicle and make a reasonable effort to switch to night rate usage, it would be highly likely you will save significant sums of money. If you don’t have either, then it is a question of how much energy you can switch to night rate to see if it is worthwhile.
Some assumptions to the above analysis:
- ie used for price comparisons – long term Electric Ireland (55% of domestic customers in Ireland) and lowest introductory rate.
- Heat pump using 4000 kWh/ annum;
- EV using 2160 (80% of 15kWh/100kms @18000kms/annum)
- Direct debit and online billing discounts not included.
- Rural standing charge.
