HEATING GUIDE

Night Storage Heater Replacement — Complete UK Guide

Everything electricians and homeowners need to know about replacing old night storage heaters: Lot 20 compliance, wiring under BS 7671, Economy 7 tariff implications, and realistic costs for modern alternatives.

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10 min readUpdated 2026-05-18Andrew Moore, Founder of Elec-Mate

Written and reviewed by Andrew Moore, founder of Elec-Mate, against BS 7671:2018+A4:2026, IET Guidance Note 3 and the IET On-Site Guide.

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Key Takeaways

  • 1Old night storage heaters manufactured before 2018 are likely non-compliant with the Lot 20 ErP Directive, which sets minimum energy performance standards for local space heaters. Replacement with a compliant model is required if the unit is being sold or supplied new.
  • 2Each storage heater circuit typically runs on a dedicated radial circuit — commonly 2.5mm² cable on a 16A MCB for heaters up to 3kW, or 4mm² on a 20A MCB for larger units. Always confirm the heater rating plate before sizing cable and protection.
  • 3Switching from night storage heaters to panel heaters or infrared heating eliminates the need for a dual-rate Economy 7 tariff and the associated off-peak controller. A full electrical assessment of the existing circuits is essential before like-for-like replacement.
  • 4Air source heat pumps (ASHPs) require a dedicated supply from the consumer unit, typically on a 32A or 40A circuit with appropriate cable sizing. Part P notification is required for new circuits in England.
  • 5Infrared panel heaters operate at lower wattages (typically 350W to 1,000W) and can often be connected to existing socket circuits or fused spurs, simplifying installation and reducing rewiring costs.
01 · Heating Guide

Why Replace Night Storage Heaters?

Night storage heaters were the dominant form of electric heating in UK homes built between the 1960s and 1990s. They work by storing heat in ceramic bricks during off-peak hours (typically overnight on an Economy 7 tariff) and releasing that heat gradually during the day. While this approach made sense when off-peak electricity was substantially cheaper, several factors have changed the economics significantly.

  • Poor controllability — older storage heaters have limited ability to respond to changing weather or occupancy. Heat stored overnight is released throughout the day regardless of whether the property is occupied, wasting energy and money.
  • Lot 20 non-compliance — heaters manufactured before January 2018 do not meet the Ecodesign minimum performance standards. Lot 20 requires electronic thermostats, open window detection, and adaptive charge control as minimum standards for new heaters placed on the market.
  • Narrowing Economy 7 price differential — the gap between Economy 7 day and night rates has narrowed over recent years. The benefit of off-peak charging is less pronounced than it was in the 1980s, making the storage heater proposition less attractive financially.
  • Heat pump compatibility — properties heated by storage heaters are increasingly prime candidates for air source heat pump (ASHP) retrofits, particularly following the introduction of the Boiler Upgrade Scheme (BUS) grant of up to \u00a37,500 for ASHPs in England and Wales.

For electricians, storage heater replacements are a growing area of domestic work. Understanding the wiring implications, tariff considerations, and Lot 20 requirements is essential for providing accurate advice and completing compliant installations. Use the

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02 · Heating Guide

Modern Alternatives to Night Storage Heaters

There are three main categories of modern electric heating that can replace night storage heaters, each with different installation requirements, running costs, and suitability depending on the property type and insulation standard.

1. Lot 20-Compliant Storage Heaters

  • Direct replacement for existing heaters — same circuit, same connection point. Modern units include electronic thermostats, open window detection, and 24/7 programming. Brands include Dimplex Quantum, Elnur, and Creda.
  • Best suited to properties with existing Economy 7 wiring and meter. Minimal electrical work required. Cost: \u00a3400 to \u00a3900 per heater supplied and fitted.

2. Electric Panel Heaters

  • Convection or fan-assisted heaters rated typically 750W to 2,500W. No off-peak charging — heat on demand only. Can connect to existing spur circuits or fused connection units. Wi-Fi or smart thermostat models offer good control.
  • Economy 7 tariff no longer required. Single-rate tariff may be more cost-effective. Supply cost: \u00a3150 to \u00a3500 per unit. Installation: \u00a350 to \u00a3150 per heater if connecting to existing circuits.

3. Infrared Panel Heaters

  • Radiant heat panels rated typically 350W to 1,000W. Heat objects and people directly rather than the air, making them more efficient in poorly insulated rooms. Can be ceiling or wall mounted. Suitable for most domestic circuits.
  • Installation is straightforward — most panels connect via a standard 13A plug or fused spur. Supply cost: \u00a3200 to \u00a3600 per panel. No Off-Peak tariff needed.

4. Air Source Heat Pumps

  • Whole-house heating solution. Requires wet underfloor heating or suitable radiators (low-flow temperature compatible). Typical system cost: \u00a38,000 to \u00a315,000. Boiler Upgrade Scheme grant of \u00a37,500 available in England and Wales.
  • Requires a dedicated electrical supply — typically a 32A or 40A radial circuit with appropriate cable sizing per BS 7671. Part P notification required. MCS certification needed to access grant funding.
03 · Heating Guide

Economy 7 Tariff Implications

Economy 7 is a dual-rate electricity tariff offering cheaper overnight electricity (typically between midnight and 07:00, though the exact hours vary by supplier and region) with a higher day rate. The tariff requires a dual-rate meter — either an older electromechanical type or a modern smart meter configured for two rates.

Night storage heaters are designed specifically to exploit this tariff by charging during the cheap-rate period. When storage heaters are removed or replaced with on-demand heaters, the Economy 7 arrangement may no longer be beneficial because:

  • Higher day rate applies to all on-demand heating — panel heaters and infrared heaters operate during the day at the higher Economy 7 day rate, which is typically 20 to 30% more expensive than a standard single-rate tariff for the same consumption.
  • Switching tariff requires a meter change — if moving from Economy 7 to a single-rate tariff, the supplier may need to reconfigure the smart meter or replace an older dual-rate meter. This is arranged through the energy supplier and is usually free.
  • Economy 7 remains beneficial for electric vehicle charging — if the property has or plans to install an electric vehicle charge point, Economy 7 overnight cheap rates may still provide value for overnight EV charging even without storage heaters.
  • Dual-rate wiring may be present — properties with storage heaters often have a separate Economy 7 consumer unit or a dual-tariff wiring arrangement with a separate off-peak circuit. When replacing heaters, check whether this dedicated wiring can be repurposed or must be decommissioned.
04 · Heating Guide

Lot 20 Regulations Explained

The Lot 20 Ecodesign requirements derive from EU Commission Regulation (EU) 2015/1188 and have been retained in UK law through the Ecodesign for Energy-Related Products and Energy Information Regulations 2021. They set minimum energy performance standards for local space heaters, a category that includes electric storage heaters, panel heaters, and infrared heaters placed on the UK market on or after 1 January 2018.

Minimum Requirements for Electric Heaters (Lot 20)

  • Electronic thermostat with minimum 1\u00b0C precision
  • Open window detection — heater reduces output when a rapid temperature drop is detected (window opened)
  • Adaptive start — heater learns the thermal characteristics of the room and adjusts heat-up timing
  • Weekly programming — 24/7 time programming as a minimum
  • Presence detection capability (for heaters above certain wattage thresholds)

Pre-2018 storage heaters — particularly older manual dial-controlled units — do not meet these requirements. They can still legally be used in a property, but cannot be supplied as new. When a landlord or homeowner asks about replacement, installing a Lot 20-compliant model is the appropriate recommendation.

Electricians are not required to verify Lot 20 compliance as part of an electrical installation, but advising customers on this regulation demonstrates professional competence and protects against future complaints.

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05 · Heating Guide

Wiring Requirements Under BS 7671

Fixed electric heating installations must comply with BS 7671:2018+A4:2026 (the Wiring Regulations). The key requirements for storage heater and replacement heating circuits are covered in Part 5 (Selection and Erection of Equipment) and Chapter 43 (Protection Against Overcurrent).

Circuit Sizing for Fixed Heating

  • Up to 2kW (8.7A): 2.5mm\u00b2 twin and earth cable, 16A MCB (Type B)
  • Up to 3kW (13A): 2.5mm\u00b2 twin and earth cable, 16A MCB (Type B)
  • Up to 3.68kW (16A): 2.5mm\u00b2 twin and earth cable, 20A MCB (Type B)
  • 3.68kW to 4.6kW (20A): 4mm\u00b2 twin and earth cable, 20A MCB (Type B)
  • Over 4.6kW: 6mm\u00b2 or larger — calculate per BS 7671 Chapter 43 based on design current, installation method, and grouping derating factors
  • RCD protection — fixed electric heaters installed in domestic premises must have 30mA RCD protection under Regulation 411.3.3. This applies to heaters in all rooms including bedrooms and living rooms.
  • Local isolation — each fixed heater requires a means of isolation accessible without the use of a tool (Regulation 537.2). A double-pole fused spur with neon indicator is the standard solution.
  • Part P notification — new circuits for fixed heating in dwellings in England are notifiable under Part P of the Building Regulations. Use a registered competent person scheme (NICEIC, NAPIT, ELECSA) for self-certification.

Before replacing storage heaters, always test the existing circuit: verify the earth loop impedance, insulation resistance, and RCD operation time. Record findings on an or minor works certificate as appropriate.

06 · Heating Guide

Typical Replacement Costs

Replacement costs vary significantly depending on the heating type chosen, the number of heaters, whether existing circuits are suitable, and whether any consumer unit upgrades are required.

  • Like-for-like Lot 20 storage heater replacement: \u00a3450 to \u00a3950 per unit (supply and fit). No new circuits required if existing wiring is satisfactory.
  • Electric panel heaters: \u00a3200 to \u00a3650 per heater (supply and fit). May require new circuits or fused spurs. Additional cost if Economy 7 wiring needs decommissioning.
  • Infrared panel heaters: \u00a3250 to \u00a3700 per panel (supply and fit). Wiring is typically simpler. Ceiling-mounted panels may require more labour for cable routing.
  • Air source heat pump (full system): \u00a38,000 to \u00a315,000 installed. Boiler Upgrade Scheme grant of \u00a37,500 reduces net cost. MCS certification required to claim grant.
  • Consumer unit upgrade (if required): \u00a3500 to \u00a31,200 for a dual RCD or RCBO consumer unit. Often required where the existing board lacks sufficient ways or adequate RCD protection.
07 · Heating Guide

For Electricians — Using Elec-Mate for Storage Heater Jobs

Storage heater replacement jobs typically involve an initial inspection, a minor works or full installation certificate, and sometimes a consumer unit upgrade. Elec-Mate provides the tools you need to manage the paperwork efficiently on-site.

Night Storage Heater Replacement — Frequently Asked Questions

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